|
OSHA Instruction CPL 2.106 February 9, 1996 Office of Health
Compliance Assistance SUBJECT: Enforcement Procedures and Scheduling for Occupational
Exposure to Tuberculosis A.
Purpose. This instruction provides uniform inspection procedures and
guidelines to be followed when conducting inspections and issuing citations
under Section 5(a)(1) of the OSH Act and pertinent standards for employees
who are occupationally exposed to tuberculosis. B.
Scope. This instruction applies OSHA-wide. C.
References. 1. OSHA Instruction CPL 2.103, September 26,
1994, Field Inspection Reference Manual (FIRM). 2. OSHA Instruction CPL
2.45B, June 15, 1985, The Revised Field Operations Manual (FOM). 3. American
Public Health Association - 1990 or current edition, Control of Communicable
Diseases in Man. 4. OSHA Instruction CPL 2-2.20B, CH-3, August 22, 1994. Occupational
Safety and Health Administration Technical Manual Chapter No. 7. 5. OSHA
Instruction, ADM 1-31, the IMIS Enforcement Data Processing Manual. 6. OSHA
Instruction ADM 1-32, Enforcement User Skills Manual (for those Area Offices
still using the NCR system). 7. Centers for Disease Control and Prevention
(CDC), Biosafety in Microbiological and Biomedical Laboratories, 3rd Edition,
or current edition. 8. Department of Health and Human Services, Public Health
Service, 42 CFR Part 84; Final Rule 9. Centers for Disease Control and
Prevention (CDC); Guidelines for Preventing the transmission of mycobacterium
tuberculosis in Health Care Facilities, 1994; MMWR October 26, 1994 Vol. 43,
No. RR-13. D. Action.
OSHA Regional
Administrators and Area Directors shall use this instruction to ensure
uniformity when performing inspections for occupational exposures to
tuberculosis (TB). The Directorate of Compliance Programs shall provide
support as necessary to assist the Regional Administrators and Area Directors
in enforcing this directive. Issuance of this directive cancels the
Memorandum to Regional Administers dated October 8, 1993, and entitled
Enforcement Policy and Procedures for Occupational Exposure to Tuberculosis. E.
Federal Program Change. This is a federal program change which impacts
state programs. 1. The Regional Administrator (RA) shall
ensure that this change is promptly forwarded to each state designee using a
format consistent with the Plan Change Two-way Memorandum in Appendix A,
State Plan Policies and Procedures Manual (SPM). 2. The RA shall explain the
content of this change to the state designee as required. 3. The state shall
respond to this change within 70 days in accordance with paragraph
I.1.a.(2).(a). and (b)., Part I, Chapter III of the SPM. 4. The state's
acknowledgment shall include (a) the state's plan to adopt and implement an
identical change, (b) the state's plan to develop an alternative, which is as
effective, or the reasons why no change is necessary to maintain a program
which is as effective. The state shall submit a plan supplement within six
months in accordance with I.1.a.(3).(c)., Part I, Chapter III of the SPM. 5. The
RA shall advise state designees of the following: a. In order to ensure a
sound and consistent national enforcement and litigation strategy in relation
to complex issues addressed by this instruction, state implementation of the
procedures in this instruction, or comparable state procedures, must be
carefully coordinated with OSHA. b. The state is also responsible for
extending coverage under its procedures for addressing occupational exposure
to tuberculosis to the public sector employees in workplaces covered by this
instruction. c. The Directorate of Technical Support is available to assist
the states in locating expert witnesses (see paragraph M., expert witnesses).
Also, the Directorate of Compliance Programs will provide support to the
states through the RA to assist in the enforcement of this directive. 6. The
RA shall review policies, instructions, and guidelines issued by the state to
determine that this change has been communicated to state compliance
personnel. F.
Definitions. For a complete list of definitions applicable to
tuberculosis please refer to the list of definitions in the 1994 CDC
guidelines found in Appendix A beginning on page 113. G.
Background. Since 1985, the incidence of tuberculosis (TB) in the
general U.S. population has increased approximately 14 percent, reversing a
30-year downward trend. In 1993, 25,313 new cases of TB were reported in the
United States. Increases in the incidence of TB have been observed in some
geographic areas; these increases are related partially to the high risk for
TB among immunosuppressed persons, particularly those infected with human
immunodeficiency virus (HIV). Other factors (e.g., socioeconomic) have also
contributed to these increases. Outbreaks have occurred in hospitals, correctional
institutions, homeless shelters, nursing homes, and residential care
facilities for AIDS patients. During 1994 and 1995 there has been a decrease
in the number of TB cases in the United States that is likely been due to
increased awareness and efforts in the prevention and control of TB,
including the implementation of TB control measures recommended by the CDC
and required by OSHA. Recently, drug resistant strains of M.
tuberculosis have become a serious concern and cases of multi-drug-resistant
(MDR) TB have occurred in forty states. In a recent New York City study, 33%
of cases had organisms resistant to the two most effective drugs available
for treating the disease. When organisms are resistant to both drugs, the
course of the treatment increases from six months to 18-24 months, and the
cure rate decreases from 100% to 60% or less. In a 1992 American Hospital
Association survey/CDC survey, 90 of 729 (13%) respondents reported
nosocomial TB transmission to health care workers. More than 80% of those
facilities experienced TB skin test conversions among workers. More than 100
cases of active TB disease in health care workers were known to CDC and
reported to Congress by Dr. William Roper in the Spring of 1993. Twelve (12)
health care workers have died. Nationwide, at least several hundred employees
have become infected and required medical treatment after workplace exposure
to TB. In general, persons who become infected with TB have approximately a
10% risk for developing active TB in their lifetimes. M. tuberculosis is
carried through the air in tiny infectious droplet nuclei of 1 to 5 microns
in diameter. These droplets may be generated when a person with pulmonary and
laryngeal TB disease coughs, speaks, sings, sneezes, or spits. When inhaled by
susceptible persons, the mycobacteria in these droplets may become
established in the lungs and, in some cases, spread throughout the body. After
an interval of months, years, or even decades, the initial infection may then
progress to clinical illness (i.e., tuberculosis disease). Transmission of TB
is most likely to occur from persons with pulmonary or laryngeal TB that are
not on effective anti-TB therapy and who have not been placed in respiratory
isolation. In occupational healthcare settings, where patients with TB are
seen, workers exposed to tuberculosis droplet nuclei are at increased risk of
infection with exposure to TB. Certain high-risk medical procedures that are
cough-inducing or aerosol generating can further increase the risk of
infection in health-care workers. The employer's obligations are those set
forth in the Occupational Safety and Health Act (OSH Act) of 1970. Recommendations
for preventing the transmission of TB for health care settings were
originally established with the 1990 CDC Guidelines. In October, of 1994,
those guidelines were revised and published (Appendix A). The new guidelines
emphasize the control of TB through an effective TB infection control
program. Under these guidelines the control of TB is to be accomplished through
the early identification, isolation, and treatment of persons with TB, use of
engineering and administrative procedures to reduce the risk of exposure, and
through the use of respiratory protection. OSHA believes these guidelines
reflect an industry recognition of the hazard as well as appropriate, widely
recognized, and accepted standards of practice to be followed by employers in
carrying out their responsibilities under the OSH Act. H.
Inspection Scheduling and Scope 1. The evaluation of occupational exposure to
TB shall be conducted in response to employee complaints, related
fatality/catastrophes, or as part of all industrial hygiene inspections
conducted in workplaces where the CDC has identified workers as having a
greater incidence of TB infection than in the general population. The degree
of risk of occupational exposure of a worker to TB will vary based on a
number of factors discussed in detail by the CDC (Appendix A, pg. 4-5). These
workplaces have been the subject of reports issued by the CDC which provide
recommendations for the control of tuberculosis. Specifically, these
workplaces are as follows: a. health care facilities b. correctional
institutions c. long-term care facilities for the elderly d. homeless
shelters e. drug treatment centers Note: Health-care facilities
include hospitals where patients with confirmed or suspect TB are treated or
to which they are transported. Coverage of non-hospital health care settings
(i.e., doctors' offices, clinics, etc.) includes only personnel present
during the performance of high hazard procedures on suspect or active TB
patients. Dental health care personnel are covered by the directive only if
they treat suspect or active patients in a hospital or correctional facility.
Homeless shelters - due to a variety of circumstances, the control of TB in
homeless shelters presents unique problems for the protection of workers. Shelters
must establish protocols that provide for rapid early identification followed
by immediate transfer of suspect cases if the shelters have elected not to
treat these patients. 2. All inspections in these workplaces shall include a
review of the employer's plans for employee TB protection, if any. Such plans
may include the infection control program, respiratory protection and skin
testing. Employee interviews and site observations are an integral part of
the process evaluation. 3. Complaints received from state and local
government employees who are outside federal jurisdiction in federal
enforcement states shall be referred to the appropriate agency by the Area
Office. I.
Inspection Procedures. The procedure given in the FIRM, Chapter II,
shall be followed except as modified in the following sections: 1. Health care facilities generally have
internal infection control and employee health programs. This function may be
performed by a team or individual. Upon entry, the CSHO shall request the
presence of the infection control director and employee occupational health
professional responsible for occupational health hazard control. Other
individuals who will be responsible for providing records pertinent to the
inspection may include: training director, facilities engineer, director of
nursing, etc. 2. The CSHO shall establish whether or not the facility has had
a suspect or confirmed TB case within the previous six (6) months from the
opening conference to determine coverage under the OSH Act. This
determination may be based upon interviews and, in a hospital, a review of
the infection control data. 3. If the facility has had a suspect or confirmed
TB case within the previous six months, the CSHO shall proceed with the TB
portion of the inspection. The CSHO shall verify implementation of the
employer's plans for TB protection through employee interviews and direct
observation where feasible. Professional judgment shall be used to identify
which areas of a facility must be inspected during the walkthrough (e.g.,
emergency rooms, respiratory therapy areas, bronchoscopy suites, and morgue).
After review of the facility plans for worker TB protection, employee
interviews combined with an inspection of appropriate areas of the facility,
shall be used to determine compliance. 4. CSHOs who perform smoke-trail
visualization tests should review the protocol in Appendix B of this
directive. 5. CSHOs should be prepared to present to the employer the
material safety data sheet (MSDS) for the smoke that is released on a
smoke-trail visualization. J.
Compliance Officer Protection 1. Area Directors or Assistant Area Directors
shall ensure that CSHOs performing TB related inspections are familiar with
the CDC Guidelines, terminology, and are adequately trained through either
course work or field/work experience in health care settings. Consultation
with the regional TB coordinators is encouraged prior to beginning such
inspections. 2. CSHOs shall not enter occupied respiratory isolation [AFB
(acid fast bacilli)] rooms to evaluate compliance unless, in their
determination entry is required to document a violation. Prior to entry CSHOs
will discuss the need for entry with the Area Director. Photographs or video
taping where practical shall be used for case documentation. Under no
circumstances shall photographing or videotaping of patients be done. CSHO's
must take all necessary precautions to assure and protect patient
confidentiality. 3. CSHOs shall exercise professional judgement and extreme
caution when engaging in activities that may involve potential exposure to
TB. CSHOs normally shall establish the existence of hazards and adequacy of
work practices through employee interviews and shall observe them in a manner
which prevents exposure (e.g., through an observation window where
available). 4. On rare occasions when entry into potentially hazardous areas
is judged necessary (e.g., where the CSHO determines that direct observation
of a high hazard procedure is necessary), the CSHO shall be properly equipped
as required by the facility, this directive, and following consultation with
the CSHO's supervisor. Since CSHOs' respiratory protection is used in more
than one type of industry they shall use their negative pressure elastomeric
face piece respirators equipped with HEPA filters as the minimum level of
respiratory protection. 5. CSHOs who conduct TB inspections shall have been
offered the TB skin tests. CSHOs exposed to an individual(s) with active
infectious TB shall receive a follow-up examination and follow Sections J.
and K. of Appendix A beginning on page 37. Note: A "TB Skin Test"
means the intradermal injection (Mantoux Method) of tuberculin antigen
(usually PPD) with subsequent measurement of the induration by designated,
trained personnel. 6. If an isolation room is occupied by a patient with
confirmed or suspect TB or has not been adequately purged when a smoke-trail
test is performed, then the CSHO should assume that the isolation room is not
under negative pressure. Under such circumstances CSHOs shall wear a negative
pressure HEPA respirator when performing air tests as described in Appendix B
or if entry into the room is determined to be necessary. K.
Citation Policy. Relevant chapters of the FIRM shall be followed when
preparing and issuing citations for hazards related to TB. 1. The following requirements apply when
citing hazards found in target workplaces. Employers must comply with the
provisions of these requirements whenever an employee may be occupationally
exposed to TB: Section 5(a)(1) -- General Duty Clause and Executive Order 12196, Section 1-201(a) for Federal facilities.
29 CFR 1910.134 -- Respiratory Protection 29
CFR 1910.145 -- Accident Prevention Signs and Tags 29 CFR 1910.20 -- Access
to Employee Exposure and Medical Records 29 CFR 1904 -- Recording and Reporting Occupational Injuries & Illness
L.
Violations. All elements in this section must be addressed to ensure
adequate protection of employees from TB hazards. Violations of these OSHA
requirements will normally be classified as serious. 1. General Duty Clause - Section 5(a)(1).
Section 5(a)(1) provides: "Each employer shall furnish to each of his
employees employment and a place of employment which are free from recognized
hazards that are causing or are likely to cause death or serious physical
harm to his employees." a. Section 5(a)(1) citations must meet the
requirements outlined in the FIRM, and shall be issued only when there is no
standard that applies to the particular hazard. The hazard, not the absence
of a particular means of abatement, is the basis for a general duty clause
citation. All applicable abatement methods identified as correcting the same
hazard shall be issued under a single 5(a)(1) citation. b. Recognition, for
purposes of citing section 5(a)(1), is shown by the CDC Guidelines for the
types of exposures detailed below because the CDC is an acknowledged body of
experts familiar with the hazard. c. Citations shall be issued to employers
with employees working in one of the workplaces where the CDC has identified
workers as having a higher incidence of TB infection than the general
population, when the employees are not provided appropriate protection and
who have exposure as defined below: 1. Exposure to the exhaled air of an
individual with suspected or confirmed pulmonary TB disease, or Note:
A suspected case is one in which the facility has identified an individual as
having symptoms consistent with TB. The CDC has identified the symptoms to
be: productive cough, coughing up blood, weight loss, loss of appetite,
lethargy/weakness, night sweats, or fever. 2. Employee exposure without
appropriate protection to a high hazard procedure performed on an individual
with suspected or confirmed infectious TB disease and which has the potential
to generate infectious airborne droplet nuclei. Examples of high hazard procedures
include aerosolized medication treatment, bronchoscopy, sputum induction,
endotracheal intubation and suctioning procedures, emergency dental,
endoscopic procedures, and autopsies conducted in hospitals. d. If a citation
under 5(a)(1) is justified, the citation, after setting forth the SAVE for
section 5(a)(1), shall state: Section 5(a)(1) of the Occupational Safety and
Health Act of 1970: The employer did not furnish employment and a place of
employment which were free from recognized hazards that were causing or
likely to cause death or serious physical harm to employees exposed to the
hazard of being infected with Mycobacterium tuberculosis through unprotected
contact with [specify group such as patients, inmates, clients, etc.] who
was/were infectious or suspected to be infectious with tuberculosis in that:
[list deficiencies] Feasible and useful abatement methods for reducing this
hazard, as recommended by the CDC, include, but are not limited to: [list
abatement methods]. e. The following are examples of feasible and useful
abatement methods, which must be implemented to abate the hazard. Deficiencies
found in any category can result in the continued existence of a serious
hazard and may, therefore, allow citation under 5(a)(1). 1. Early
Identification of Patient/Client. The employer shall implement a protocol
for the early identification of individuals with active TB. See Appendix A
pages 19-30. 2. Medical Surveillance: a. Initial Exams. The employer,
in covered workplaces, shall offer TB skin tests (at no cost to the
employees) to all current potentially exposed employees and to all new
employees prior to exposure. A two-step baseline shall be used for new
employees who have an initially negative PPD test result and who have not had
a documented negative TB skin test result during the preceding 12 months (See
Appendix A, pg. 63). TB skin tests shall be offered at a time and location
convenient to workers. Follow-up and treatment evaluations are also to be
offered at no cost to the workers. Note: The reading and
interpretation of the TB skin tests shall be performed by a qualified
individual as described in the CDC Guidelines. b. Periodic Evaluations. TB
skin testing shall be conducted every three (3) months for workers in high
risk categories, every six (6) months for workers in intermediate risk
categories, and annually for low risk personnel (The CDC has defined the
criteria for high, intermediate, and low risk categories, see Appendix A, pg.
8-17). Workers with a documented positive TB skin test who have received
treatment for disease or preventive therapy for infection are exempt from the
TB skin test but must be informed periodically about the symptoms of TB and
the need for immediate evaluation of any pulmonary symptoms suggestive of TB
by a physician or trained health care provider to determine if symptoms of TB
disease have developed. Note: If the facility has not completed a risk
assessment the CSHO shall review the TB related records to establish required
testing frequencies for the facility and areas of the facility. c.
Reassessment following exposure or change in health. Workers who experience
exposure to an individual with suspect or confirmed infectious TB for whom
infection control precautions have not been taken shall be managed according
to CDC recommendations (Appendix A). An employee who develops symptoms of TB
disease shall be immediately evaluated according to the CDC Guidelines. 3. Case
Management of Infected Employees shall include the following: a. Protocol
for New Converters. Conversion to a positive TB skin test shall be followed
as soon as possible, by appropriate physical, laboratory, and radiographic
evaluations to determine whether the employee has infectious TB disease. (See
Appendix A, pg. 65). b. Work Restrictions for Infectious Employees. See
Appendix A, page 41. 4. Worker Education and Training. Training and
information to ensure employee knowledge of such issues as the mode of TB
transmission, its signs and symptoms, medical surveillance and therapy, and
site specific protocols including the purpose and proper use of controls
shall be provided to all current employees and to new workers upon hiring. (See
Appendix A, pgs. 36-37) Training should be repeated as needed. Workers shall
be trained to recognize, and report to a designated person, any patients or
clients with symptoms suggestive of infectious TB and instructed on the post
exposure protocols to be followed in the event of an exposure incident. (See
Appendix A, pg. 23) 5. Engineering Controls. The use of each control measure
must be based on its ability to abate the hazard. a. Individuals with
suspected or confirmed infectious TB disease must be placed in a respiratory
acid-fast bacilli (AFB) isolation room. High hazard procedures on individuals
with suspected or confirmed infectious TB disease must be performed in AFB
treatment rooms, AFB isolation rooms, booths, and/or hoods. AFB isolation
refers to a negative pressure room or an area that exhausts room air directly
outside or through HEPA filters if recirculation is unavoidable. b. Isolation
and treatment rooms in use by individuals with suspected or confirmed
infectious TB disease shall be kept under negative pressure to induce airflow
into the room from all surrounding areas (e.g., corridors, ceiling plenums,
plumbing chases, etc.). (See Appendix A, Supplement No. 3, page 76) Note:
The employer must assure that AFB isolation rooms are maintained under
negative pressure. At a minimum, the employer must use nonirritating smoke
trails or some other indicator to demonstrate that direction of airflow is
from the corridor into the isolation/treatment room with the door closed. If
an anteroom exists, direction of airflow must be demonstrated at the inner
door between the isolation/treatment room and the anteroom. (See Appendix B)
c. Air exhausted from AFB isolation or treatment rooms must be safely
exhausted directly outside and not recirculated into the general ventilation
system. (See Appendix A, Supplement No. 3, page 87). In circumstances where
recirculation is unavoidable, HEPA filters must be installed in the duct
system from the room to the general ventilation system. (See Appendix A,
Supplement No. 3, page 82). For these HEPA filters, a regularly scheduled
monitoring program to demonstrate as-installed effectiveness should include;
1) recognized field test method, 2) acceptance criteria, and 3) testing
frequencies (see Appendix A, Supplement No. 3, page 85). The air handling
system should be appropriately marked with a TB warning where maintenance
personnel would have access to the duct work, fans, or filters for
maintenance or repair activities. d. In order to avoid leakage, all
potentially contaminated air which is ducted through the facility must be
kept under negative pressure until it is discharged safely outside (i.e.,
away from occupied areas and air intakes), or e. The air from isolation and
treatment rooms must be decontaminated by a recognized process (e.g., HEPA
filter) before being recirculated back to the isolation/treatment room. The
use of UV radiation as the sole means of decontamination shall not be used. The
CDC Guidelines allow the use of UV in waiting rooms, emergency rooms,
corridors, and the like where patients with undiagnosed TB could potentially
contaminate the air. (See appendix A, pg. 90) Note: The opening and
closing of doors in an isolation or treatment room which is not equipped with
an anteroom compromises the ability to maintain negative pressure in the
room. For these rooms, the employer should utilize a combination of controls
and practices to minimize spillage of contaminated air into the corridor. Recognized
controls and practices include, but are not limited to: minimizing entry to
the room; adjusting the hydraulic closer to slow the door movement and reduce
displacement effects; adjusting doors to swing into the room where fire codes
permit; avoiding placement of room exhaust intake near the door; etc. f. If
high-hazard procedures are performed within AFB isolation or treatment rooms
without benefit of source control ventilation or local exhaust ventilation
(e.g., hood, booth, tent, etc.), and droplets are released into the
environment (e.g., coughing), then a purge time interval must be imposed
during which personnel must use a respirator when entering the room. (See
Appendix A, pg. 35 and Suppl. 3, Table S3-1) g. Interim or supplemental
ventilation units equipped with HEPA filters as described in Appendix A pgs.
70-73 are acceptable. 2. Respiratory Protection - 29 CFR 1910.134(a)(2)
and (b). The standard provides in part: "Respirators shall be
provided by the employer when such equipment is necessary to protect the
health of the employee. The employer shall provide the respirators which are
applicable and suitable for the purpose intended. The employer shall be
responsible for the establishment and maintenance of a respiratory protective
program which shall include the requirement outlined in paragraph (b) of this
section." a. Requirements for a minimal acceptable program. The
1994 CDC Guidelines specify standard performance criteria for respirators for
exposure to TB. These criteria include (see appendix A pg 97): 1. The ability
to filter particles 1 um in size in the unloaded state with a filter
efficiency of greater than or equal to 95% (i.e., filter leakage of less than
or equal to 5%), given flow rates of up to 50L per minute. 2. The ability to
be qualitatively or quantitatively fit tested in a reliable way to obtain a
face-seal leakage of less than or equal to 10%. 3. The ability to fit the
different facial sizes and characteristics of health care workers which can
usually be met by making the respirators available in at least three sizes. 4.
The ability to be checked for face piece fit, in accordance with OSHA
standards and good industrial hygiene practice, by health care workers each time
they put on their respirator. b. Under the new NIOSH criteria, filter
materials would be tested at a flow rate of 85 L/minute for penetration by
particles with a median aerodynamic diameter of 0.3 um and, if certified
would be placed in one of the following categories: Type 100 (99.7%
efficient), Type 99 (99% efficient), and Type 95 (95% efficient). NIOSH has
determined that these categories of respirators are effective against TB. Based
upon these criteria, the minimally acceptable level of respiratory protection
for TB is the Type 95 Respirator. The classes of these air-purifying,
particulate respirators to be certified are described under 42 CFR Part 84
Subpart K. See Volume 60 of the Federal Register, page 30338 (June 8, 1995). Until
these classes of respirators are commercially available the minimal
acceptable respiratory protection meeting the criteria will remain the HEPA
respirator (see Appendix A, pg 98). The following respiratory protection
measures must be addressed: 1. Employees wear HEPA or respirators certified
under 42 CFR Part 84 Subpart K in the following circumstances: a. When
workers enter rooms housing individuals with suspected or confirmed
infectious TB. b. When workers are present during the performance of high
hazard procedures on individuals who have suspected or confirmed infectious
TB. c. When emergency-medical-response personnel or others transport, in a
closed vehicle, an individual with suspected or confirmed infectious TB. Note:
If a facility chooses to use disposable respirators as part of their
respiratory protection program, their reuse by the same health care worker is
permitted as long as the respirator maintains its structural and functional
integrity and the filter material is not physically damaged or soiled. The
facility must address the circumstances in which a disposable respirator will
be considered to be contaminated and not available for reuse. 2. The
following sample language is provided for citations which are warranted under
1910.134(a)(2): "The employer did not provide respirators which were
applicable and suitable for the purpose intended, nor was a respiratory
protection program established which included the requirements outlined in 29
CFR 1910.134(b): (a) Employees were given a [surgical mask or list manufacturer/model
number] respirator for protection against airborne Mycobacterium tuberculosis
when entering isolation rooms or performing high hazard procedures [including
vehicular transporting if applicable]. They shall use NIOSH approved
respirators (HEPA or those certified under 42 CFR Part 84 Subpart K). NIOSH
approved respirators providing greater protection would also be acceptable. 3.
When respiratory protection (including disposable respirators) is required, a
complete respiratory protection program must be in place in accordance with
29 CFR 1910.134(b). 3. Access to employee medical and exposure records: 29
CFR 1910.20. a. A record concerning employee exposure to TB is an
employee exposure record within the meaning of 29 CFR 1910.20. b. A record of
TB skin test results and medical evaluations and treatment are employee
medical records within the meaning of 29 CFR 1910.20. Where known, the
workers exposure record should contain a notation of the type of TB, to which
the employee was exposed to (e.g., multidrug resistant TB). c. These records
shall be handled according to 29 CFR 1913.10 in order for the CSHO to
determine compliance with 29 CFR 1910.20. 4. Accident prevention signs and
tags: 29 CFR 1910.145. a. In accordance with 1910.145(f)(8), a warning
shall be posted outside the Respiratory isolation or treatment room. 1910.145(f)(4)
requires that a signal word (i.e. "STOP", "HALT", or
"NO ADMITTANCE") or biological hazard symbol be presented as well
as a major message (e.g., "special respiratory isolation",
"Respiratory isolation", or AFB isolation). A description of the
necessary precautions, e.g., respirators must be donned before entering. Respiratory
isolation rooms in an emergency department or a message referring one to the
nursing station for instruction must also be posted. b. The employer shall
also use biological hazard tags on air transport components (e.g., fans,
ducts, filters) which identify TB hazards to employees associated with
working on air systems that transport contaminated air (See Appendix A, page
85). c. The standard provides in part: 29 CFR 1910.145(e)(4): Biological
hazard warning signs were not used to signify the actual or potential
presence of a biohazard and to identify equipment, containers, rooms,
materials, experimental animals, or combinations thereof, which contain, or
are contaminated with viable hazardous agents: Sample violation language: a.
On or about [date], warning signs posted outside respiratory (Respiratory)
isolation or treatment rooms did not state the entry requirement of wearing
HEPA filtered respirators. Abatement Note: Warning signs must be
posted on respiratory isolation or treatment rooms stating "pulmonary
isolation", "respiratory isolation," or "AFB
isolation." The sign must state specifically the precautions required to
interact with those patients. Indicators on patient records or tags on
corpses, printed in language or symbols easily recognized by employees are
additional methods to achieve this purpose. 5. OSHA 200 log - 29 CFR 1904:
a. For OSHA Form 200 record keeping purposes, both tuberculosis infections
(positive TB skin test) and tuberculosis disease are recordable in the high
risk setting referenced in section H.1. A positive skin test for
tuberculosis, even on initial testing (except pre-assignment screening) is
recordable on the OSHA 200 log because there is a presumption of
work-relatedness in these settings unless there is clear documentation that
an outside exposure occurred. Note: In this case preassignment means the same
as pre employment and initial testing is the same as baseline testing. b. If
the employee's tuberculosis infection which was entered on the OSHA 200 log
progresses to tuberculosis disease during the five-year maintenance period,
the original entry for the infection shall be updated to reflect the new
information. Because it is difficult to determine if tuberculosis disease
resulted from the source indicated by the skin test conversion or from
subsequent exposures, only one case should be entered to avoid double
counting. c. A positive TB skin test provided within two weeks of employment
does not have to be recorded on the OSHA 200 forms. However, the initial test
must be performed prior to any potential workplace exposure within the
initial two weeks of employment. M.
Expert Witness. The Directorate of Technical Support will assist
Regional Offices and the States in locating expert witnesses. Expert
witnesses must be contacted before issuance of citations. 1. In the event that a 5(a)(1) citation is
contested, proper expert witness support will be required. Issues which the
expert must be prepared to address include: a. The risk to workers associated
with the exposure circumstances. b. Existence, feasibility and utility of
abatement measures. c. Recognition of the hazard in the industry. 2. Expert
witnesses may also be necessary in other cases, particularly those involving
29 CFR 1910.134. N.
Recording in the IMIS. A TB-related inspection is any health
inspection conducted to investigate the presence or alleged presence of TB disease
(i.e., a referral or complaint inspection). 1. When a TB-related inspection is conducted,
complete the OSHA-1 as for any inspection and enter the code "N 02
TB" in Item 42, Optional Information. EXAMPLE: Type ID Value N 2 TB
2. When an OSHA-7 is completed and the
complaint alleges the presence of TB hazards, enter the code "N 02
TB" in Item 46, Optional Information. 3. When an OSHA-90 is completed
and the referral alleges the presence of TB hazards, enter the code "N
02 TB" in Item, 26, Optional Information. 4. All IMIS case file data for
TB-related inspections conducted since October 1, 1990, shall be modified to
include the appropriate TB code. O.
Referrals 1. When a complaint or inquiry is received
from a source in a state plan regarding occupational exposure to TB, the Area
Office shall refer it to the state plan designee for action. 2. When a
complaint or inquiry regarding occupational exposure to TB in a state or
local government health care facility is received in a state without an
OSHA-approved state plan, the Regional Administrator shall refer it to the
appropriate State public health agency or local health agency. P.
Pre-citation Review. Citations proposed pursuant to this program shall
be reviewed prior to issuance, by the Regional Administrator and Regional
Office Solicitor for consistency with these procedures. The Directorate of
Technical Support shall be contacted to establish expert witness support. The
Office of Health Compliance Assistance shall be provided with a copy of all
citations issued related to TB during the first 6 months of this directive. Joseph
A. Dear Assistant Secretary Distribution:
National, Regional, and Area Offices All Compliance Officers State Designees
NIOSH Regional Program Directors 7(c)(1) Consultation Project Managers Appendix No. A October 28, 1994/Vol. 43/No.RR-13 MMWR
Recommendations and Reports MORBIDITY
AND MORTALITY WEEKLY REPORT
---------------------------------------------------------------------------- Guidelines for preventing the Transmission of Mycobacterium Tuberculosis in Health-Care Facilities, 1994 U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Centers for Disease Control and Prevention (CDC) Atlanta, Georgia 30333 Contents Executive Summary ...................................................1 I. Introduction ...................................................2 A. Purpose of
Document .......................................2 B. Epidemiology,
Transmission, and Pathogenesis of TB ........4 C. Risk for Nosocomial
Transmission of M. tuberculosis .......5 D. Fundamentals of TB Infection
Control ......................6 II. Recommendations ................................................8 A. Assignment of
Responsibility ..............................8 B. Risk Assessment,
Development of the TB Infection-Control Plan, and Periodic Reassessment
.........8 1. Risk assessment ......................................8 a.
General .........................................8 b. Community TB profile
...........................17 c. Case surveillance
..............................17 d. Analysis of HCW PPD test screening data
........17 e. Review of TB patient medical records ...........18 f.
Observation of TB infection-control practices ......................................19
g. Engineering evaluation .........................19 2. Development of the
TB Infection-Control Plan ........19 3. Periodic Reassessment
...............................19 4. Examples of Risk Assessment
.........................22 C. Identifying, Evaluating, and Initiating
Treatment for Patients Who May Have Active TB ......................23 1. Identifying
patients who may have active TB .........23 2. Diagnostic evaluation for
active TB .................24 3. Initiation of treatment for suspected or
confirmed TB ........................................25 D. Management of
Patients Who May Have Active TB in Ambulatory-Care Settings and Emergency
Departments .......25 E. Management of Hospitalized Patients Who Have
Confirmed or Suspected TB ................................27 1. Initiation of
isolation for TB ......................27 Use of trade names is for identification only
and does not imply endorsement by the Public Health Service or the U.S.
Department of Health and Human
Services. Copies can be purchased from Superintendent
of Documents, U.S. Government
Printing Office, Washington, DC 20402-9325. Telephone: (202) 783-3238. 2. TB isolation practices ..............................28 3. The TB isolation room
...............................29 4. Discontinuation of TB isolation
.....................30 5. Discharge planning
..................................31 F. Engineering Control Recommendations
......................31 1. General ventilation
.................................31 2. Additional engineering control
approaches ...........32 a. HEPA filtration
................................32 b. UVGI
...........................................32 G. Respiratory Protection
...................................33 H. Cough-inducing and
Aerosol-Generating Procedures .........34 1. General guidelines
..................................34 2. Special considerations for
bronchoscopy .............35 3. Special considerations for the administration
of aerosolized pentamidine ..........................35 I. Education and
Training of HCWs ...........................36 J. HCW Counseling, Screening,
and Evaluation ................37 1. Counseling HCWs regarding TB
........................37 2. Screening HCWs for active TB
........................38 3. Screening HCWs for latent TB infection
..............38 4. Evaluation and management of HCWs who have positive PPD
test results or active TB ..............40 a. Evaluation
.....................................40 b. Routine and follow-up chest
radiographs ........40 c. Workplace restrictions .........................41
1) Active TB .................................41 2) Latent TB infection
.......................41 K. Problem Evaluation .......................................41
1. Investigating PPD test conversions and active TB in HCWs
..........................................42 a. Investigating PPD test
conversions in HCWs .....42 b. Investigating cases of active TB in HCWs
.......47 2. Investigating possible patient-to-patient transmission of M.
tuberculosis .....................48 3. Investigating contacts of patients
and HCWs who have infectious TB ..............................48 L.
Coordination with the Public Health Department ...........49 M. Additional
Considerations for Selected Areas in Health-Care Facilities and Other
Health-Care Settings .................................................50 1. Selected
areas in health-care facilities ............50 a. Operating rooms
................................50 b. Autopsy rooms
..................................51 c. Laboratories
...................................51 2. Other health-care settings
..........................51 a. Emergency medical services
.....................51 b. Hospices .......................................52
c. Long-term care facilities ......................52 d. Correctional
facilities ........................52 e. Dental settings
................................52 f. Home-health-care settings
......................53 g. Medical offices
................................54 Supplement 1: Determining the Infectiousness of a TB Patient ......57 Supplement 2: Diagnosis and Treatment of Latent TB Infection and
Active TB
......................................................59 I.
Diagnostic Procedures for TB Infection and Disease .......59 A. PPD Skin Testing and
Anergy Testing .................59 1. Application and reading of PPD skin
tests ......59 2. Interpretation of PPD skin tests ...............60 a.
General ...................................60 b. HCWs
......................................61 3. Anergy testing
.................................61 4. Pregnancy and PPD skin testing
.................61 5. BCG vaccination and PPD skin testing ...........63 6. The
booster phenomenon .........................63 B. Chest Radiography
...................................64 C. Bacteriology
........................................64 II.
II. Preventive Therapy for Latent TB Infection and Treatment of Active
TB
...................................65 A. Preventive Therapy for Latent TB
Infection ..........65 B. Treatment of Patients Who Have Active TB
............66 Supplement 3: Engineering Controls ................................69 I.
Introduction .............................................69
II.
Ventilation
..............................................69 A. Local Exhaust Ventilation
...........................70 1. Enclosing devices ..............................70 2. Exterior-devices
...............................71 3. Discharge exhaust from booths, tents,
and hoods ......................................71 B. General Ventilation
.................................73 1. Dilution and removal
...........................73 a. Types of general ventilation systems
......73 b. Ventilation rates .........................74 2. Airflow patterns
within rooms (air mixing) .....74 3. Airflow direction in the facility
..............76 a. Directional airflow .......................76 b. Negative
pressure for achieving directional airflow .......................76 4. Achieving
negative pressure in a room ..........76 a. Pressure differential
.....................76 b. Alternate methods for achieving negative pressure
.........................77 c. Monitoring negative pressure ..............78
C. HEPA filtration .....................................81 1. Use of HEPA
filtration when exhausting air to the outside
.................................82 2. Recirculation of HEPA-filtered air to
other areas of a facility ......................82 3. Recirculation of
HEPA-filtered air within a room ..................................82 a. Fixed
room-air recirculation systems ......84 b. Portable room-air recirculation
units .....84 c. Evaluation of room-air recirculation systems and units
.........................85 4. Installing, maintaining, and monitoring HEPA
filters ...................................85 D. TB Isolation Rooms and
Treatment Rooms ..............86 1. Preventing the escape of droplet nuclei
from the room ..................................87 2. Reducing the
concentration of droplet nuclei in the room .............................87
3. Exhaust from TB isolation rooms and treatment rooms
................................87 4. Alternatives to TB isolation rooms
.............87 III.
UVGI
..........................................................88 A. Applications
.............................................89 1. Duct irradiation
....................................89 2. Upper-room air irradiation
..........................89 B. Limitations
..............................................90 C. Safety Issues
............................................91 D. Exposure Criteria for UV
Radiation .......................92 E. Maintenance and Monitoring
...............................93 1. Labeling and posting
................................93 2. Maintenance
.........................................94 3. Monitoring
..........................................95 Supplement 4: Respiratory Protection ..............................97 I. Considerations for Selection of Respirators ................97 A. Performance Criteria for Personal Respirators for Protection Against Transmission of M. tuberculosis ........................................97 B. Specific Respirators ................................98 C. The Effectiveness of Respiratory Protective Devices .............................................99 1. Face-seal leakage ..............................99 2. Filter leakage ................................100 3. Fit testing ...................................100 4. Fit checking ..................................101 5. Reuse of respirators ..........................101 II. Implementing a Personal Respiratory Protection Program .......102
Supplement 5: Decontamination-Cleaning, Disinfecting, and Sterilizing
of Patient-Care Equipment .............................105 References
........................................................106 Glossary
..........................................................113 Index
.............................................................121 List of Tables
...............................................132 List of Figures
..............................................132 Acknowledgments Drafts
of this document have been reviewed by leaders of numerous medical,
scientific, public health, and labor organizations and others expert in
tuberculosis, acquired immunodeficiency syndrome, infection control, hospital
epidemiology, microbiology, ventilation, industrial hygiene, nursing, dental
practice, or emergency medical services. We thank the many organizations and
individuals for their thoughtful comments, suggestions, and assistance. TB Infection-Control Guidelines Work Group Carmine J. Bozzi Dale R. Burwen, M.D. Samuel W. Dooley, M.D. Patricia M. Simone, M.D. National Center for Prevention Services Consuelo Beck-Sague, M.D. Elizabeth A. Bolyard, R.N., M.P.H. William R. Jarvis, M.D. National Center for Infectious Diseases Philip J. Bierbaum Christine A. Hudson, M.P.H. Robert T. Hughes Linda S. Martin, Ph.D. Robert J. Mullan, M.D. National Institute for Occupational Safety
and Health Brian M. Willis, J.D., M.P.H. Office of the Director
Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities, 1994 Executive Summary This
document updates and replaces all previously published guidelines for the
prevention of Mycobacterium tuberculosis transmission in health-care
facilities. The purpose of this revision is to emphasize the importance of a)
the hierarchy of control measures, including administrative and engineering
controls and personal respiratory protection; b) the use of risk assessments
for developing a written tuberculosis (TB) control plan; c) early
identification and management of persons who have TB; d) TB screening programs
for health-care workers (HCWs); e) HCW training and education; and f) the
evaluation of TB infection-control programs. Transmission
of M. tuberculosis is a recognized risk to patients and HCWs in health-care
facilities. Transmission is most likely to occur from patients who have
unrecognized pulmonary or laryngeal TB, are not on effective anti-TB therapy,
and have not been placed in TB isolation. Several recent TB outbreaks in
health-care facilities, including outbreaks of multidrug-resistant TB, have
heightened concern about nosocomial transmission. Patients who have
multidrug-resistant TB can remain infectious for prolonged periods, which
increases the risk for nosocomial and/or occupational transmission of M.
tuberculosis. Increases in the incidence of TB have been observed in some
geographic areas; these increases are related partially to the high risk for
TB among immunosuppressed persons, particularly those infected with human
immunodeficiency virus (HIV). Transmission of M. tuberculosis to HIV-infected
persons is of particular concern because these persons are at high risk for
developing active TB if they become infected with the bacteria. Thus,
health-care facilities should be particularly alert to the need for
preventing transmission of M. tuberculosis in settings in which HIV-infected
persons work or receive care. Supervisory
responsibility for the TB infection-control program should be assigned to a
designated person or group of persons who should be given the authority to
implement and enforce TB infection-control policies. An effective TB
infection-control program requires early identification, isolation, and
treatment of persons who have active TB. The primary emphasis of TB
infection-control plans in health-care facilities should be achieving these
three goals by the application of a hierarchy of control measures, including
a) the use of administrative measures to reduce the risk for exposure to
persons who have infectious TB, b) the use of engineering controls to prevent
the spread and reduce the concentration of infectious droplet nuclei, and c)
the use of personal respiratory protective equipment in areas where there is
still a risk for exposure to M. tuberculosis (e.g., TB isolation rooms). Implementation
of a TB infection-control program requires risk assessment and development of
a TB infection-control plan; early identification, treatment, and isolation
of infectious TB patients; effective engineering controls; an appropriate
respiratory protection program; HCW TB training, education, counseling, and
screening; and evaluation of the program's effectiveness. Although
completely eliminating the risk for transmission of M. tuberculosis in all
health-care facilities may not be possible at the present time, adherence to
these guidelines should reduce the risk to persons in these settings. Recently,
nosocomial TB outbreaks have demonstrated the substantial morbidity and
mortality among patients and HCWs that have been associated with incomplete
implementation of CDC's Guidelines for Preventing the Transmission of
Tuberculosis in Health-Care Facilities, with Special Focus on HIV-Related
Issues published in 1990.* Follow-up investigations at some of these
hospitals have documented that complete implementation of measures similar or
identical to those in the 1990 TB Guidelines significantly reduced or
eliminated nosocomial transmission of M. tuberculosis to patients and/or
HCWs. __________ *
CDC. Guidelines for Preventing the Transmission of Tuberculosis in
Health-Care Facilities, with Special Focus on HIV-Related Issues. MMWR
1990;39(No. RR-17). I. Introduction A. Purpose of Document In April 1992, the National
MDR-TB Task Force published the National Action Plan to Combat
Multidrug-Resistant Tuberculosis (1). The publication was a response to
reported nosocomial outbreaks of tuberculosis (TB), including outbreaks of
multidrug-resistant TB (MDR-TB), and the increasing incidence of TB in some
geographic areas. The plan called for the update and revision of the guidelines
for preventing nosocomial transmission of Mycobacterium tuberculosis
published December 7, 1990 (2). Public meetings were held in October 1992 and
January 1993 to discuss revision of the 1990 TB Guidelines (2). CDC received
considerable input on various aspects of infection control, including
health-care worker (HCW) education; administrative controls (e.g., having
protocols for the early identification and management of patients who have
TB); the need for more specific recommendations regarding ventilation; and
clarification on the use of respiratory protection in health-care settings. On
the basis of these events and the input received, on October 12, 1993, CDC
published in the Federal Register the Draft Guidelines For Preventing the
Transmission of Tuberculosis in Health-Care Facilities, Second Edition (3). During
and after the 90-day comment period following publication of this draft,
CDC's TB Infection-Control Guidelines Work Group received and reviewed more
than 2,500 comments. The purpose of this document is to make recommendations
for reducing the risk for transmitting M. tuberculosis to HCWs, patients,
volunteers, visitors, and other persons in these settings. The information
also may serve as a useful resource for educating HCWs about TB. These recommendations
update and replace all previously published CDC recommendations for TB
infection control in health-care facilities (2,4). The recommendations in
this document are applicable primarily to inpatient facilities in which
health care is provided (e.g., hospitals, medical wards in correctional
facilities, nursing homes, and hospices). Recommendations applicable to
ambulatory-care facilities, emergency departments, home-health-care settings,
emergency medical services, medical offices, dental settings, and other
facilities or residential settings that provide medical care are provided in
separate sections, with cross-references to other sections of the guidelines
if appropriate. Designated personnel at health-care facilities should conduct
a risk assessment for the entire facility and for each area* and occupational
group, determine the risk for nosocomial or occupational transmission of M.
tuberculosis, and implement an appropriate TB infection-control program. The
extent of the TB infection-control program may range from a simple program
emphasizing administrative controls in settings where there is minimal risk
for exposure to M. tuberculosis, to a comprehensive program that includes
administrative controls, engineering controls, and respiratory protection in
settings where the risk for exposure is high. In all settings, administrative
measures should be used to minimize the number of HCWs exposed to M.
tuberculosis while still providing optimal care for TB patients. HCWs
providing care to patients who have TB should be informed about the level of
risk for transmission of M. tuberculosis and the appropriate control measures
to minimize that risk. __________ *
Area: a structural unit (e.g., a hospital ward or laboratory) or functional
unit (e.g., an internal medicine service) in which HCWs provide services to
and share air with a specific patient population or work with clinical
specimens that may contain viable M. tuberculosis organisms. The risk for
exposure to M. tuberculosis in a given area depends on the prevalence of TB
in the population served and the characteristics of the environment. In this document, the term "HCWs"
refers to all the paid and unpaid persons working in health-care settings who
have the potential for exposure to M. tuberculosis. This may include, but is
not limited to, physicians; nurses; aides; dental workers; technicians;
workers in laboratories and morgues; emergency medical service (EMS)
personnel; students; part-time personnel; temporary staff not employed by the
health-care facility; and persons not involved directly in patient care but
who are potentially at risk for occupational exposure to M. tuberculosis
(e.g., volunteer workers and dietary, housekeeping, maintenance, clerical,
and janitorial staff). Although the purpose of this document is to make
recommendations for reducing the risk for transmission of M. tuberculosis in
health-care facilities, the process of implementing these recommendations
must safeguard, in accordance with applicable state and federal laws, the
confidentiality and civil rights of persons who have TB. B. Epidemiology, Transmission, and
Pathogenesis of TB
The prevalence of TB is not distributed evenly throughout all segments of the
U.S. population. Some subgroups or persons have a higher risk for TB either
because they are more likely than other persons in the general population to
have been exposed to and infected with M. tuberculosis or because their
infection is more likely to progress to active TB after they have been
infected (5). In some cases, both of these factors may be present. Groups of
persons known to have a higher prevalence of TB infection include contacts of
persons who have active TB, foreign-born persons from areas of the world with
a high prevalence of TB (e.g., Asia, Africa, the Caribbean, and Latin
America), medically underserved populations (e.g., some African-Americans,
Hispanics, Asians and Pacific Islanders, American Indians, and Alaskan
Natives), homeless persons, current or former correctional-facility inmates,
alcoholics, injecting-drug users, and the elderly. Groups with a higher risk
for progression from latent TB infection to active disease include persons
who have been infected recently (i.e., within the previous 2 years), children
less than 4 years of age, persons with fibrotic lesions on chest radiographs,
and persons with certain medical conditions (i.e., human immunodeficiency
virus [HIV] infection, silicosis, gastrectomy or jejuno-ileal bypass, being
greater than or equal to 10% below ideal body weight, chronic renal failure
with renal dialysis, diabetes mellitus, immunosuppression resulting from
receipt of high-dose corticosteroid or other immunosuppressive therapy, and
some malignancies)(5). M. tuberculosis is carried in airborne particles, or
droplet nuclei, that can be generated when persons who have pulmonary or
laryngeal TB sneeze, cough, speak, or sing (6). The particles are an
estimated 1-5 um in size, and normal air currents can keep them airborne for
prolonged time periods and spread them throughout a room or building (7). Infection
occurs when a susceptible person inhales droplet nuclei containing M.
tuberculosis, and these droplet nuclei traverse the mouth or nasal passages,
upper respiratory tract, and bronchi to reach the alveoli of the lungs. Once
in the alveoli, the organisms are taken up by alveolar macrophages and spread
throughout the body. Usually within 2-10 weeks after initial infection with
M. tuberculosis, the immune response limits further multiplication and spread
of the tubercle bacilli; however, some of the bacilli remain dormant and
viable for many years. This condition is referred to as latent TB infection. Persons
with latent TB infection usually have positive purified protein derivative
(PPD)-tuberculin skin-test results, but they do not have symptoms of active
TB, and they are not infectious. In general, persons who become infected with
M. tuberculosis have approximately a 10% risk for developing active TB during
their lifetimes. This risk is greatest during the first 2 years after infection.
Immunocompromised persons have a greater risk for the progression of latent
TB infection to active TB disease; HIV infection is the strongest known risk
factor for this progression. Persons with latent TB infection who become
coinfected with HIV have approximately an 8%-10% risk per year for developing
active TB (8). HIV-infected persons who are already severely immunosuppressed
and who become newly infected with M. tuberculosis have an even greater risk
for developing active TB (9-12). The probability that a person who is exposed
to M. tuberculosis will become infected depends primarily on the
concentration of infectious droplet nuclei in the air and the duration of
exposure. Characteristics of the TB patient that enhance transmission include
a) disease in the lungs, airways, or larynx; b) presence of cough or other
forceful expiratory measures; c) presence of acid-fast bacilli (AFB) in the
sputum; d) failure of the patient to cover the mouth and nose when coughing
or sneezing; e) presence of cavitation on chest radiograph; f) inappropriate
or short duration of chemotherapy; and g) administration of procedures that
can induce coughing or cause aerosolization of M. tuberculosis (e.g., sputum
induction). Environmental factors that enhance the likelihood of transmission
include a) exposure in relatively small, enclosed spaces; b) inadequate local
or general ventilation that results in insufficient dilution and/or removal
of infectious droplet nuclei; and c) recirculation of air containing
infectious droplet nuclei. Characteristics of the persons exposed to M.
tuberculosis that may affect the risk for becoming infected are not as well
defined. In general, persons who have been infected previously with M.
tuberculosis may be less susceptible to subsequent infection. However,
reinfection can occur among previously infected persons, especially if they
are severely immunocompromised. Vaccination with Bacille of Calmette and
Guerin (BCG) probably does not affect the risk for infection; rather, it
decreases the risk for progressing from latent TB infection to active TB
(13). Finally, although it is well established that HIV infection increases
the likelihood of progressing from latent TB infection to active TB, it is
unknown whether HIV infection increases the risk for becoming infected if
exposed to M. tuberculosis. C. Risk for Nosocomial Transmission of M.
tuberculosis
Transmission of M. tuberculosis is a recognized risk in health-care
facilities (14-22). The magnitude of the risk varies considerably by the type
of health-care facility, the prevalence of TB in the community, the patient
population served, the HCW's occupational group, the area of the health-care
facility in which the HCW works, and the effectiveness of TB
infection-control interventions. The risk may be higher in areas where
patients with TB are provided care before diagnosis and initiation of TB
treatment and isolation precautions (e.g., in clinic waiting areas and
emergency departments) or where diagnostic or treatment procedures that
stimulate coughing are performed. Nosocomial transmission of M. tuberculosis
has been associated with close contact with persons who have infectious TB
and with the performance of certain procedures (e.g., bronchoscopy [17],
endotracheal intubation and suctioning [18], open abscess irrigation [20],
and autopsy [21,22]). Sputum induction and aerosol treatments that induce
coughing may also increase the potential for transmission of M. tuberculosis
(23,24). Personnel of health-care facilities should be particularly alert to
the need for preventing transmission of M. tuberculosis in those facilities
in which immunocompromised persons (e.g., HIV-infected persons) work or
receive care -- especially if cough-inducing procedures, such as sputum
induction and aerosolized pentamidine treatments, are being performed. Several
TB outbreaks among persons in health-care facilities have been reported
recently (11,24-28; CDC, unpublished data). Many of these outbreaks involved
transmission of multidrug-resistant strains of M. tuberculosis to both
patients and HCWs. Most of the patients and some of the HCWs were
HIV-infected persons in whom new infection progressed rapidly to active
disease. Mortality associated with those outbreaks was high (range: 43%-93%).
Furthermore, the interval between diagnosis and death was brief (range of
median intervals: 4-16 weeks). Factors contributing to these outbreaks
included delayed diagnosis of TB, delayed recognition of drug resistance, and
delayed initiation of effective therapy -- all of which resulted in prolonged
infectiousness, delayed initiation and inadequate duration of TB isolation,
inadequate ventilation in TB isolation rooms, lapses in TB isolation
practices and inadequate precautions for cough-inducing procedures, and lack
of adequate respiratory protection. Analysis of data collected from three of
the health-care facilities involved in the outbreaks indicates that
transmission of M. tuberculosis decreased significantly or ceased entirely in
areas where measures similar to those in the 1990 TB Guidelines were
implemented (2,29-32). However, several interventions were implemented
simultaneously, and the effectiveness of the separate interventions could not
be determined. D. Fundamentals of TB Infection Control An effective TB infection-control
program requires early identification, isolation, and effective treatment of
persons who have active TB. The primary emphasis of the TB infection-control
plan should be on achieving these three goals. In all health-care facilities,
particularly those in which persons who are at high risk for TB work of
receive care, policies and procedures for TB control should be developed,
reviewed periodically, and evaluated for effectiveness to determine the
actions necessary to minimize the risk for transmission of M. tuberculosis. The
TB infection-control program should be based on a hierarchy of control
measures. The first level of the hierarchy, and that which affects the
largest number of persons, is using administrative measures intended
primarily to reduce the risk for exposing uninfected persons to persons who
have infectious TB. These measures include a) developing and implementing
effective written policies and protocols to ensure the rapid identification,
isolation, diagnostic evaluation, and treatment of persons likely to have TB;
b) implementing effective work practices among HCWs in the health-care
facility (e.g., correctly wearing respiratory protection and keeping doors to
isolation rooms closed); c) educating, training, and counseling HCWs about
TB; and d) screening HCWs for TB infection and disease. The second level of
the hierarchy is the use of engineering controls to prevent the spread and
reduce the concentration of infectious droplet nuclei. These controls include
a) direct source control using local exhaust ventilation, b) controlling
direction of airflow to prevent contamination of air in areas adjacent to the
infectious source, c) diluting and removing contaminated air via general
ventilation, and d) air cleaning via air filtration or ultraviolet germicidal
irradiation (UVGI). The first two levels of the hierarchy minimize the number
of areas in the health-care facility where exposure to infectious TB may
occur, and they reduce, but do not eliminate, the risk in those few areas
where exposure to M. tuberculosis can still occur (e.g., rooms in which
patients with known or suspected infectious TB are being isolated and
treatment rooms in which cough-inducing or aerosol-generating procedures are
performed on such patients). Because persons entering such rooms may be
exposed to M. tuberculosis, the third level of the hierarchy is the use of
personal respiratory protective equipment in these and certain other
situations in which the risk for infection with M. tuberculosis may be
relatively higher. Specific measures to reduce the risk for transmission of
M. tuberculosis include the following: * Assigning to specific persons in the
health-care facility the supervisory responsibility for designing,
implementing, evaluating, and maintaining the TB infection-control program
(Section II.A). * Conducting a risk assessment to evaluate the risk for
transmission of M. tuberculosis in all areas of the health-care facility,
developing a written TB infection-control program based on the risk
assessment, and periodically repeating the risk assessment to evaluate the
effectiveness of the TB infection-control program (Section II.B). *
Developing, implementing, and enforcing policies and protocols to ensure
early identification, diagnostic evaluation, and effective treatment of patients
who may have infectious TB (Section II.C; Suppl. 2). * Providing prompt
triage for and appropriate management of patients in the outpatient setting
who may have infectious TB (Section II.D). * Promptly initiating and
maintaining TB isolation for persons who may have infectious TB and who are
admitted to the inpatient setting (Section II.E; Suppl. 1). * Effectively
planning arrangements for discharge (Section II.E). * Developing, installing,
maintaining, and evaluating ventilation and other engineering controls to
reduce the potential for airborne exposure to M. tuberculosis (Section II.F;
Suppl. 3). * Developing, implementing, maintaining, and evaluating a
respiratory protection program (Section II.G; Suppl. 4). * Using precautions
while performing cough-inducing procedures (Section II.H; Suppl. 3). *
Educating and training HCWs about TB, effective methods for preventing
transmission of M. tuberculosis, and the benefits of medical screening
programs (Section II.I). * Developing and implementing a program for routine
periodic counseling and screening of HCWs for active TB and latent TB
infection (Section II.J; Suppl. 2). * Promptly evaluating possible episodes
of M. tuberculosis transmission in health-care facilities, including PPD
skin-test conversions among HCWs, epidemiologically associated cases among
HCWs or patients, and contacts of patients or HCWs who have TB and who were
not promptly identified and isolated (Section II.K). * Coordinating
activities with the local public health department, emphasizing reporting,
and ensuring adequate discharge follow-up and the continuation and completion
of therapy (Section II.L). II. Recommendations A. Assignment of Responsibility * Supervisory responsibility for
the TB infection-control program should be assigned to a designated person or
group of persons with expertise in infection control, occupational health,
and engineering. These persons should be given the authority to implement and
enforce TB infection-control policies. * If supervisory responsibility is
assigned to a committee, one person should be designated as the TB contact
person. Questions and problems can then be addressed to this person. B. B. Risk Assessment, Development of
the TB Infection-Control Plan, and Periodic Reassessment 1. Risk assessment a.
General * TB infection-control measures for each health-care facility should
be based on a careful assessment of the risk for transmission of M.
tuberculosis in that particular setting. The first step in developing the TB
infection-control program should be to conduct a baseline risk assessment to
evaluate the risk for transmission of M. tuberculosis in each area and
occupational group in the facility (Table 1, Figure 1). Appropriate
infection-control interventions can then be developed on the basis of actual
risk. Risk assessments should be performed for all inpatient and outpatient
settings (e.g., medical and dental offices). * Regardless of risk level, the
management of patients with known or suspected infectious TB should not vary.
However, the index of suspicion for infectious TB among patients, the
frequency of HCW PPD skin testing, the number of TB isolation rooms, and
other factors will depend on whether the risk for transmission of M.
tuberculosis in the facility, area, or occupational group is high,
intermediate, low, very low, or minimal. * The risk assessment should be
conducted by a qualified person or group of persons (e.g., hospital
epidemiologists, infectious disease specialists, pulmonary disease
specialists, infection-control practitioners, health-care administrators,
occupational health personnel, engineers, HCWs, or local public health
personnel). * The risk assessment should be conducted for the entire facility
and for specific areas within the facility (e.g., medical, TB, pulmonary, or
HIV wards; HIV, infectious disease, or pulmonary clinics; and emergency
departments or other areas where TB patients might receive care or where
cough-inducing procedures are performed). This should include both inpatient
and outpatient areas. In addition, risk assessments should be conducted for
groups of HCWs who work throughout the facility rather than in a specific
area (e.g., respiratory therapists; bronchoscopists; environmental services,
dietary, and maintenance personnel; and students, interns, residents, and
fellows). TABLE 1. Elements of a risk assessment for tuberculosis (TB) in health-care facilities ----------------------------------------------------------------------------- 1.
Review the community TB profile (from public health department data). 2.
Review the number of TB patients who were treated in each area of area of the
facility (both inpatient and outpatient). (This information can be obtained
by analyzing laboratory surveillance data and by reviewing discharge
diagnoses or medical and infection-control records.) 3.
Review the drug-susceptibility patterns of TB isolates of patients who were
treated at the facility. 4.
Analyze purified protein derivative (PPD)-tuberculin skin-test results of
health-care workers (HCWs), by area or by occupational group for HCWs not
assigned to a specific area (e.g., respiratory therapists). 5.
To evaluate infection-control parameters, review medical records of a sample
of TB patients seen at the facility. Calculate intervals from: * admission until TB
suspected; * admission until TB evaluation performed; * admission until
acid-fast bacilli (AFB) specimens ordered; * AFB specimens ordered until AFB
specimens collected; * AFB specimens collected until AFB smears performed and
reported; * AFB specimens collected until cultures performed and reported; *
AFB specimens collected until species identification conducted and reported;
* AFB specimens collected until drug-susceptibility tests performed and
reported; * admission until TB isolation initiated; * admission until TB
treatment initiated; and * duration of TB isolation. Obtain the following
additional information: * Were appropriate criteria used for discontinuing
isolation? * Did the patient have a history or prior admission to the
facility * Was the TB treatment regimen adequate? * Were follow-up sputum
specimens collected properly? * Was appropriate discharge planning conducted? 6.
Perform an observational review of TB infection control practices. 7.
Review the most recent environmental evaluation and maintenance procedures. ____________________________________________________________________________ (For Figure 1, see printed copy) * Classification of risk for a facility, for
a specific area, and for a specific occupational group should be based on a)
the profile of TB in the community; b) the number of infectious TB patients
admitted to the area or ward, or the estimated number of infectious TB
patients to whom HCWs in an occupational group may be exposed; and c) the
results of analysis of HCW PPD test conversions (where applicable) and
possible person-to-person transmission of M. tuberculosis (Figure 1). * All
TB infection-control programs should include periodic reassessments of risk. The
frequency of repeat risk assessments should be based on the results of the
most recent risk assessment (Table 2, Figure 1). * The
"minimal-risk" category applies only to an entire facility. A
"minimal-risk" facility does not admit TB patients to inpatient or
outpatient areas and is not located in a community with TB (i.e., counties or
communities in which TB cases have not been reported during the previous
year). Thus, there is essentially no risk for exposure to TB patients in the
facility. This category may also apply to many outpatient settings (e.g.,
many medical and dental offices). (For Table 2, see printed copy) * The "very low-risk" category
generally applies only to an entire facility. A very low-risk facility is one
in which a) patients with active TB are not admitted to inpatient areas but
may receive initial assessment and diagnostic evaluation or outpatient
management in outpatient areas (e.g., ambulatory-care and emergency
departments) and b) patients who may have active TB and need inpatient care
are promptly referred to a collaborating facility. In such facilities, the
outpatient areas in which exposure to patients with active TB could occur
should be assessed and assigned to the appropriate low-, intermediate-, or
high-risk category. Categorical assignment will depend on the number of TB
patients examined in the area during the preceding year and whether there is
evidence of nosocomial transmission of M. tuberculosis in the area. If TB
cases have been reported in the community, but no patients with active TB
have been examined in the outpatient area during the preceding year, the area
can be designated as very low risk (e.g., many medical offices). The
referring and receiving facilities should establish a referral agreement to
prevent inappropriate management and potential loss to follow-up of patients
suspected of having TB during evaluation in the triage system of a very
low-risk facility. In some facilities in which TB patients are admitted to
inpatient areas, a very low-risk protocol may be appropriate for areas (e.g.,
administrative areas) or occupational groups that have only a very remote
possibility of exposure to M. tuberculosis. The very low-risk category may
also be appropriate for outpatient facilities that do not provide initial
assessment of persons who may have TB, but do screen patients for active TB
as part of a limited medical screening before undertaking specialty care
(e.g., dental settings). * Low-risk" areas or occupational groups are
those in which a) the PPD test conversion rate is not greater than that for
areas or groups in which occupational exposure to M. tuberculosis is unlikely
or than previous conversion rates for the same area or group, b) no clusters*
of PPD test conversions have occurred, c) person-to-person transmission of M.
tuberculosis has not been detected, and d) fewer than six TB patients are
examined or treated per year. __________ *
Cluster: two or more PPD skin-test conversions occurring within a 3-month
period among HCWs in a specific area or occupational group, and epidemiologic
evidence suggests occupational (nosocomial) transmission. * "Intermediate-risk" areas or
occupational groups are those in which a) the PPD test conversion rate is not
greater than that for areas or groups in which occupational exposure to M.
tuberculosis is unlikely or than previous conversion rates for the same area
or group, b) no clusters of PPD test conversions have occurred, c)
person-to-person transmission of M. tuberculosis has not been detected, and
d) six or more patients with active TB are examined or treated each year. Survey
data suggest that facilities in which six or more TB patients are examined or
treated each year may have an increased risk for transmission of M.
tuberculosis (CDC, unpublished data); thus, areas in which six or more
patients with active TB are examined or treated each year (or occupational
groups in which HCWs are likely to be exposed to six or more TB patients per
year) should be classified as "intermediate risk". *
"High-risk" areas or occupational groups are those in which a) the
PPD test conversion rate is significantly greater than for areas or groups in
which occupational exposure to M. tuberculosis is unlikely or than previous
conversion rates for the same area or group, and epidemiologic evaluation
suggests nosocomial transmission; or b) a cluster of PPD test conversions has
occurred, and epidemiologic evaluation suggests nosocomial transmission of M.
tuberculosis; or c) possible person-to-person transmission of M. tuberculosis
has been detected. * If no data or insufficient data for adequate determination
of risk have been collected, such data should be compiled, analyzed, and
reviewed expeditiously. b. Community TB profile * A profile of TB in the
community that is served by the facility should be obtained from the public
health department. This profile should include, at a minimum, the incidence
(and prevalence, if available) of active TB in the community and the
drug-susceptibility patterns of M. tuberculosis isolates (i.e., the
antituberculous agents to which each isolate is susceptible and those to
which it is resistant) from patients in the community. c. Case surveillance *
Data concerning the number of suspected and confirmed active TB cases among
patients and HCWs in the facility should be systematically collected,
reviewed, and used to estimate the number of TB isolation rooms needed, to
recognize possible clusters of nosocomial transmission, and to assess the
level of potential occupational risk. The number of TB patients in specific
areas of a facility can be obtained from laboratory surveillance data on
specimens positive for AFB smears or M. tuberculosis cultures, from
infection-control records, and from databases containing information about
hospital discharge diagnoses. * Drug-susceptibility patterns of M.
tuberculosis isolates from TB patients treated in the facility should be
reviewed to identify the frequency and patterns of drug resistance. This
information may indicate a need to modify the initial treatment regimen or
may suggest possible nosocomial transmission or increased occupational risk. d. Analysis of HCW PPD test screening data * Results of HCW PPD testing should be
recorded in the individual HCW's employee health record and in a retrievable
aggregate database of all HCW PPD test results. Personal identifying
information should be handled confidentially. PPD test conversion rates
should be calculated at appropriate intervals to estimate the risk for PPD
test conversions for each area of the facility and for each specific
occupational group not assigned to a specific area (Table 2). To calculate
PPD test conversion rates, the total number of previously PPD-negative HCWs
tested in each area or group (i.e., the denominator) and the number of PPD
test conversions among HCWs in each area or group (the numerator) must be
obtained. * PPD test conversion rates for each area or occupational group
should be compared with rates for areas or groups in which occupational
exposure to M. tuberculosis is unlikely and with previous conversion rates in
the same area or group to identify areas or groups where the risk for
occupational PPD test conversions may be increased. A low number of HCWs in a
specific area may result in a greatly increased rate of conversion for that
area, although the actual risk may not be significantly greater than that for
other areas. Testing for statistical significance (e.g., Fisher's exact test
or chi square test) may assist interpretation; however, lack of statistical
significance may not rule out a problem (i.e., if the number of HCWs tested
is low, there may not be adequate statistical power to detect a significant
difference). Thus, interpretation of individual situations is necessary. * An
epidemiologic investigation to evaluate the likelihood of nosocomial
transmission should be conducted if PPD test conversions are noted (Section
II.K.1). * The frequency and comprehensiveness of the HCW PPD testing program
should be evaluated periodically to ensure that all HCWs who should be
included in the program are being tested at appropriate intervals. For
surveillance purposes, earlier detection of transmission may be enhanced if
HCWs in a given area or occupational group are tested on different scheduled
dates rather than all being tested on the same date (Section II.J.3). e. Review of TB patient medical records * The medical records of a sample of TB
patients examined at the facility can be reviewed periodically to evaluate
infection-control parameters (Table 1). Parameters to examine may include the
intervals from date of admission until a) TB was suspected, b) specimens for
AFB smears were ordered, c) these specimens were collected, d) tests were
performed, and e) results were reported. Moreover, the adequacy of the TB
treatment regimens that were used should be evaluated. * Medical record
reviews should note previous hospital admissions of TB patients before the
onset of TB symptoms. Patient-to-patient transmission may be suspected if
active TB occurs in a patient who had a prior hospitalization during which
exposure to another TB patient occurred or if isolates from two or more TB
patients have identical characteristic drug-susceptibility or DNA fingerprint
patterns. * Data from the case review should be used to determine if there is
a need to modify a) protocols for identifying and isolating patients who may
have infectious TB, b) laboratory procedures, c) administrative policies and
practices, or d) protocols for patient management. f. Observation of TB infection-control
practices
TABLE 3. Characteristics of an effective tuberculosis (TB) infection-control program* ----------------------------------------------------------------------------- I. Assignment of responsibility A. Assign responsibility for the TB
infection-control program to qualified person(s). B. Ensure that persons with
expertise in infection control, occupational health, and engineering are
identified and included. II. Risk assessment, TB infection-control plan, and periodic
reassessment A. Initial risk assessment 1. Obtain
information concerning TB in the community. 2. Evaluate data concerning TB
patients in the facility. 3. Evaluate data concerning pruified protein
derivative (PPD)-tuberculin skin-test conversions among health-care workers
(HCWs in the facility. 4. Rule out evidence of person-to-person transmission.
B. Written TB infection-control program 1. Select initial risk protocol(s).
2. Develop written TB infection-control protocols. C. Repeat risk assessment
at appropriate intervals. 1. Review current community and facility
surveillance data and PPD-tuberculin skin-test results. 2. Review records of
TB patients. 3. Observe HCW infection-control practices. 4. Evaluate
maintenance of engineering controls. III. Identification, evaluation, and treatment of patients who have TB A. Screen patients for signs and symptoms of
active TB: 1. On initial encounter in emergency department or ambulatory-care
setting. 2. Before or at the time of admission. B. Perform radiologic and
bacteriologic evaluation of patients who have signs and symptoms suggestive
of TB. C. Promptly initiate treatment. IV. Managing outpatients who have possible infectious TB A. Promptly initiate TB precautions. B. Place
patients in separate waiting areas or TB isolation rooms. C. Give patients a
surgical mask, a box of tissues, and instructions regarding the use of these
items. V. Managing inpatients who have possible infectious TB A. Promptly isolate patients who have
suspected or known infectious TB. B. Monitor the response to treatment. C.
Follow appropriate criteria for discontinuing isolation. VI. Engineering recommendations A. Design local exhaust and general
ventilation in collaboration with person who have expertise in ventilation
engineering. B. Use a single-pass air systems or air recirculation after
high-efficiency particulate air (HEPA) filtration in areas where infectious
TB patients receive care. C. Use additional measures, if needed, in areas
where TB patients may receive care. D. Design TB isolation rooms in
health-care facilities to achieve greater than or equal to 6 air changes per
hour (ACH) for existing facilities and greater than or equal to 12 ACH for
new or renovated facilities. E. Regularly monitor and maintain engineering
controls. F. TB isolation rooms that are being used should be monitored daily
to ensure they maintain negative pressure relative to the hallways and all
surrounding areas. G. Exhaust TB isolation room air to outside or, if
absolutely unavoidable, recirculate after HEPA filtration. VII. Respiratory protection A. Respiratory protective devices should meet
recommended performance criteria. B. Respiratory protection should be used by
persons entering rooms in which patients with known or suspected infectious
TB are being isolated, by HCWs when performing cough-inducing or
aerosol-generating procedures on such patients, and by persons in other
settings where administrative and engineering controls are not likely to
protect them from inhaling infectious airborne droplet nuclei. C. A
respiratory protection program is required at all facilities in which
respiratory protection is used. VII. Cough-inducing procedures A. Do not perform such procedures on TB
patients unless absolutely necessary. B. Perform such procedures in areas
that have local exhaust ventilation devices (e.g., booths or special
enclosures) or, if this is not feasible, in a room that meets the ventilation
requirements for TB isolation. C. After completion of procedures, TB patients
should remain in the booth or special enclosure until their coughing
subsides. IX. HCW TB training and education A. All HCWs should receive periodic TB
education appropriate for their work responsibilities and duties. B. Training
should include the epidemiology of TB in the facility. C. TB education should
emphasize concepts of the Pathogenesis of and occupational risk for TB. D.
Training should describe work practices that reduce the likelihood of
transmitting M. tuberculosis. X. HCW counseling and screening A. Counsel all HCWs regarding TB and TB
infection. B. Counsel all HCWs about the increased risk to immunocompromised
persons for developed active TB. C. Perform PPD skin tests on HCWs at the
beginning of their employment, and repeat PPD tests at periodic intervals. D.
Evaluate symptomatic HCWs for active TB. XI. Evaluate HCW PPD test conversions and possible nosocomial
transmission of M. tuberculosis. XII. Coordinate efforts with public health department(s) ----------------------------------------------------------------------------- *
A program such as this is appropriate for health-care facilities in which
there is a high risk for transmission of Mycobacterium tuberculosis. * After each risk assessment, the staff
responsible for TB control, in conjunction with other appropriate HCWs,
should review all TB control policies to ensure that they are effective and
meet current needs. 4. Examples of Risk Assessment Examples of six
hypothetical situations and the means by which surveillance data are used to
select a TB control protocol are described as follows: Hospital A. The
overall HCW PPD test conversion rate in the facility is 1.6%. No areas or HCW
occupational groups have a significantly greater PPD test conversion rate
than areas or groups in which occupational exposure to M. tuberculosis is
unlikely (or than previous rates for the same area or group). No clusters of
PPD test conversions have occurred. Patient-to-patient transmission has not
been detected. Patients who have TB are admitted to the facility, but no area
admits six or more TB patients per year. The low-risk protocol will be
followed in all areas. Hospital B. The overall HCW PPD test conversion
rate in the facility is 1.8%. The PPD test conversion rate for the medical
intensive-care unit rate is significantly higher than all other areas in the
facility. The problem identification process is initiated (Section II.K). It
is determined that all TB patients have been isolated appropriately. Other
potential problems are then evaluated, and the cause for the higher rate is
not identified. After consulting the public health department TB
infection-control program, the high-risk protocol is followed in the unit
until the PPD test conversion rate is similar to areas of the facility in
which occupational exposure to TB patients is unlikely. If the rate remains
significantly higher than other areas, further evaluation, including
environmental and procedural studies, will be performed to identify possible
reasons for the high conversion rate. Hospital C. The overall HCW PPD
test conversion rate in the facility is 2.4%. Rates range from 0 to 2.6% for
the individual areas and occupational groups. None of these rates is
significantly higher than rates for areas in which occupational exposure to
M. tuberculosis is unlikely. No particular HCW group has higher conversion
rates than the other groups. No clusters of HCW PPD test conversions have
occurred. In two of the areas, HCWs cared for more than six TB patients
during the preceding year. These two areas will follow the intermediate-risk
protocol, and all other areas will follow the low-risk protocol. This
hospital is located in the southeastern United States, and these conversion
rates may reflect cross-reactivity with nontuberculous mycobacteria. Hospital
D. The overall HCW PPD test conversion rate in the facility is 1.2%. In
no area did HCWs care for six or more TB patients during the preceding year. Three
of the 20 respiratory therapists tested had PPD conversions, for a rate of
15%. The respiratory therapists who had PPD test conversions had spent all or
part of their time in the pulmonary function laboratory, where induced sputum
specimens were obtained. A low-risk protocol is maintained for all areas and
occupational groups in the facility except for respiratory therapists. A
problem evaluation is conducted in the pulmonary function laboratory (Section
II.K). It is determined that the ventilation in this area is inadequate. Booths
are installed for sputum induction. PPD testing and the risk assessment are
repeated 3 months later. If the repeat testing at 3 months indicates that no
more conversions have occurred, the respiratory therapists will return to the
low-risk protocol. Hospital E. Hospital E is located in a community
that has a relatively low incidence of TB. To optimize TB services in the
community, the four hospitals in the community have developed an agreement
that one of them (e.g., Hospital G) will provide all inpatient services to
persons who have suspected or confirmed TB. The other hospitals have
implemented protocols in their ambulatory-care clinics and emergency
departments to identify patients who may have active TB. These patients are
then transferred to Hospital G for inpatient care if such care is considered
necessary. After discharge from Hospital G, they receive follow-up care in
the public health department's TB clinic. During the preceding year, Hospital
E has identified fewer than six TB patients in its ambulatory-care and
emergency departments and has had no PPD test conversions or other evidence
of M. tuberculosis transmission among HCWs or patients in these areas. These
areas are classified as low risk, and all other areas are classified as very
low risk. Hospital F. Hospital F is located in a county in which no TB
cases have been reported during the preceding 2 years. A risk assessment
conducted at the facility did not identify any patients who had suspected or
confirmed TB during the preceding year. The facility is classified as minimal
risk. C. Identifying, Evaluating, and Initiating Treatment for Patients
Who May Have Active TB The most important factors in preventing
transmission of M. tuberculosis are the early identification of patients who
may have infectious TB, prompt implementation of TB precautions for such
patients, and prompt initiation of effective treatment for those who are
likely to have TB. 1. Identifying patients who may have active TB *
Health-care personnel who are assigned responsibility for TB infection
control in ambulatory-care and inpatient settings should develop, implement,
and enforce protocols for the early identification of patients who may have
infectious TB. * The criteria used in these protocols should be based on the
prevalence and characteristics of TB in the population served by the specific
facility. These protocols should be evaluated periodically and revised
according to the results of the evaluation. Review of medical records of
patients who were examined in the facility and diagnosed as having TB may
serve as a guide for developing or revising these protocols. * A diagnosis of
TB may be considered for any patient who has a persistent cough (i.e., a
cough lasting for greater than or equal to 3 weeks) or other signs or
symptoms compatible with active TB (e.g., bloody sputum, night sweats, weight
loss, anorexia, or fever). However, the index of suspicion for TB will vary
in different geographic areas and will depend on the prevalence of TB and
other characteristics of the population served by the facility. The index of
suspicion for TB should be very high in geographic areas or among groups of
patients in which the prevalence of TB is high (Section I.B). Appropriate
diagnostic measures should be conducted and TB precautions implemented for
patients in whom active TB is suspected. 2. Diagnostic evaluation for
active TB * Diagnostic measures for identifying TB should be conducted
for patients in whom active TB is being considered. These measures include
obtaining a medical history and performing a physical examination, PPD skin
test, chest radiograph, and microscopic examination and culture of sputum or
other appropriate specimens (6,34,35). Other diagnostic procedures (e.g.,
bronchoscopy or biopsy) may be indicated for some patients (36,37). * Prompt
laboratory results are crucial to the proper treatment of the TB patient and
to early initiation of infection control. To ensure timely results,
laboratories performing mycobacteriologic tests should be proficient at both
the laboratory and administrative aspects of specimen processing. Laboratories
should use the most rapid methods available (e.g., fluorescent microscopy for
AFB smears; radiometric culture methods for isolation of mycobacteria; p-nitro-a-acetylamino-b-hydroxy-proprophenone
[NAP] test, nucleic acid probes, or high-pressure liquid chromatography
[HPLC] for species identification; and radiometric methods for
drug-susceptibility testing). As other more rapid or sensitive tests become
available, practical, and affordable, such tests should be incorporated
promptly into the mycobacteriology laboratory. Laboratories that rarely
receive specimens for mycobacteriologic analysis should refer the specimens
to a laboratory that more frequently performs these tests. * Results of AFB
sputum smears should be available within 24 hours of specimen collection
(38). * The probability of TB is greater among patients who have positive PPD
test results or a history of positive PPD test results, who have previously
had TB or have been exposed to M. tuberculosis, or who belong to a group at
high risk for TB (Section I.B). Active TB is strongly suggested if the
diagnostic evaluation reveals AFB in sputum, a chest radiograph suggestive of
TB, or symptoms highly suggestive of TB. TB can occur simultaneously in
immunosuppressed persons who have pulmonary infections caused by other
organisms (e.g., Pneumocystis carinii or Mycobacterium avium complex) and
should be considered in the diagnostic evaluation of all patients who have
symptoms compatible with TB (Suppl. 1; Suppl. 2). * TB may be more difficult
to diagnose among persons who have HIV infection (or other conditions
associated with severe suppression of cell-mediated immunity) because of a
nonclassical clinical or radiographic presentation and/or the simultaneous
occurrence of other pulmonary infections (e.g., P. carinii pneumonia and M.
avium complex). The difficulty in diagnosing TB in HIV-infected persons may
be further compounded by impaired responses to PPD skin tests (39,40), the
possibly lower sensitivity of sputum smears for detecting AFB (41), or the
overgrowth of cultures with M. avium complex in specimens from patients
infected with both M. avium complex and M. tuberculosis (42). *
Immunosuppressed patients who have pulmonary signs or symptoms that are
ascribed initially to infections or conditions other than TB should be
evaluated initially for coexisting TB. The evaluation for TB should be
repeated if the patient does not respond to appropriate therapy for the
presumed cause(s) of the pulmonary abnormalities (Suppl. 1; Suppl. 2). *
Patients with suspected or confirmed TB should be reported immediately to the
appropriate public health department so that standard procedures for
identifying and evaluating TB contacts can be initiated. 3. Initiation of
treatment for suspected or confirmed TB * Patients who have confirmed
active TB or who are considered highly likely to have active TB should be
started promptly on appropriate treatment in accordance with current
guidelines (Suppl. 2)(43). In geographic areas or facilities that have a high
prevalence of MDR-TB, the initial regimen used may need to be enhanced while
the results of drug-susceptibility tests are pending. The decision should be
based on analysis of surveillance data. * While the patient is in the
health-care facility, anti-TB drugs should be administered by directly
observed therapy (DOT), the process by which an HCW observes the patient
swallowing the medications. Continuing DOT after the patient is discharged
should be strongly considered. This decision and the arrangements for
providing outpatient DOT should be made in collaboration with the public
health department. D. Management of Patients Who May Have Active TB in
Ambulatory-Care Settings and Emergency Departments * Triage of patients
in ambulatory-care settings and emergency departments should include vigorous
efforts to promptly identify patients who have active TB. HCWs who are the
first points of contact in facilities that serve populations at risk for TB
should be trained to ask questions that will facilitate identification of
patients with signs and symptoms suggestive of TB. * Patients with signs or
symptoms suggestive of TB should be evaluated promptly to minimize the amount
of time they are in ambulatory-care areas. TB precautions should be followed
while the diagnostic evaluation is being conducted for these patients. * TB
precautions in the ambulatory-care setting should include a) placing these
patients in a separate area apart from other patients, and not in open
waiting areas (ideally, in a room or enclosure meeting TB isolation
requirements); b) giving these patients surgical masks* to wear and
instructing them to keep their masks on; and c) giving these patients tissues
and instructing them to cover their mouths and noses with the tissues when
coughing or sneezing. __________ *
Surgical masks are designed to prevent the respiratory secretions of the
person wearing the mask from entering the air. When not in a TB isolation
room, patients suspected of having TB should wear surgical masks to reduce
the expulsion of droplet nuclei into the air. These patients do not need to
wear particulate respirators, which are designed to filter the air before it
is inhaled by the person wearing the mask. Patients suspected of having or
known to have TB should never wear a respirator that has an exhalation valve,
because the device would provide no barrier to the expulsion of droplet
nuclei into the air. * TB precautions should be followed for patients
who are known to have active TB and who have not completed therapy until a
determination has been made that they are noninfectious (Suppl. 1). *
Patients with active TB who need to attend a health-care clinic should have
appointments scheduled to avoid exposing HIV-infected or otherwise severely
immunocompromised persons to M. tuberculosis. This recommendation could be
accomplished by designating certain times of the day for appointments for
these patients or by treating them in areas where immunocompromised persons
are not treated. * Ventilation in ambulatory-care areas where patients at
high risk for TB are treated should be designed and maintained to reduce the
risk for transmission of M. tuberculosis. General-use areas (e.g., waiting
rooms) and special areas (e.g., treatment or TB isolation rooms in ambulatory
areas) should be ventilated in the same manner as described for similar
inpatient areas (Sections II.E.3, II.F; Suppl. 3). Enhanced general
ventilation or the use of air-disinfection techniques (e.g., UVGI or
recirculation of air within the room through high-efficiency particulate air
[HEPA] filters) may be useful in general-use areas of facilities where many
infectious TB patients receive care (Section II.F; Suppl. 3). * Ideally,
ambulatory-care settings in which patients with TB are frequently examined or
treated should have a TB isolation room(s) available. Such rooms are not
necessary in ambulatory-care settings in which patients who have confirmed or
suspected TB are seen infrequently. However, these facilities should have a
written protocol for early identification of patients with TB symptoms and
referral to an area or a collaborating facility where the patient can be
evaluated and managed appropriately. These protocols should be reviewed on a
regular basis and revised as necessary. The additional guidelines in Section
II.H should be followed in ambulatory-care settings where cough-inducing
procedures are performed on patients who may have active TB. E. Management
of Hospitalized Patients Who Have Confirmed or Suspected TB 1. Initiation
of isolation for TB * In hospitals and other inpatient facilities, any
patient suspected of having or known to have infectious TB should be placed
in a TB isolation room that has currently recommended ventilation
characteristics (Section II.E.3; Suppl. 3). Written policies for initiating
isolation should specify a) the indications for isolation, b) the person(s)
authorized to initiate and discontinue isolation, c) the isolation practices
to follow, d) the monitoring of isolation, e) the management of patients who
do not adhere to isolation practices, and f) the criteria for discontinuing
isolation. * In rare circumstances, placing more than one TB patient together
in the same room may be acceptable. This practice is sometimes referred to as
"cohorting" Because of the risk for patients becoming superinfected
with drug-resistant organisms, patients with TB should be placed in the same
room only if all patients involved a) have culture-confirmed TB, b) have
drug-susceptibility test results available on a current specimen obtained
during the present hospitalization, c) have identical drug-susceptibility
patterns on these specimens, and d) are on effective therapy. Having isolates
with identical DNA fingerprint patterns is not adequate evidence for placing
two TB patients together in the same room, because isolates with the same DNA
fingerprint pattern can have different drug-susceptibility patterns. *
Pediatric patients with suspected or confirmed TB should be evaluated for
potential infectiousness according to the same criteria as are adults (i.e.,
on the basis of symptoms, sputum AFB smears, radiologic findings, and other
criteria) (Suppl. 1). Children who may be infectious should be placed in
isolation until they are determined to be noninfectious. Pediatric patients
who may be infectious include those who have laryngeal or extensive pulmonary
involvement, pronounced cough, positive sputum AFB smears, or cavitary TB or
those for whom cough-inducing procedures are performed (44). * The source of
infection for a child with TB is often a member of the child's family (45). Therefore,
parents and other visitors of all pediatric TB patients should be evaluated
for TB as soon as possible. Until they have been evaluated, or the source
case is identified, they should wear surgical masks when in areas of the
facility outside of the child's room, and they should refrain from visiting
common areas in the facility (e.g., the cafeteria or lounge areas). * TB
patients in intensive-care units should be treated the same as patients in
noncritical-care settings. They should be placed in TB isolation and have
respiratory secretions submitted for AFB smear and culture if they have
undiagnosed pulmonary symptoms suggestive of TB. * If readmitted to a
health-care facility, patients who are known to have active TB and who have
not completed therapy should have TB precautions applied until a
determination has been made that they are noninfectious (Suppl. 1). 2. TB
isolation practices * Patients who are placed in TB isolation should be
educated about the mechanisms of M. tuberculosis transmission and the reasons
for their being placed in isolation. They should be taught to cover their
mouths and noses with a tissue when coughing or sneezing, even while in the
isolation room, to contain liquid drops and droplets before they are expelled
into the air (46). * Efforts should be made to facilitate patient adherence
to isolation measures (e.g., staying in the TB isolation room). Such efforts
might include the use of incentives (e.g., providing them with telephones,
televisions, or radios in their rooms or allowing special dietary requests). Efforts
should also be made to address other problems that could interfere with
adherence to isolation (e.g., management of the patient's withdrawal from
addictive substances [including tobacco]). * Patients placed in isolation
should remain in their isolation rooms with the door closed. If possible,
diagnostic and treatment procedures should be performed in the isolation
rooms to avoid transporting patients through other areas of the facility. If
patients who may have infectious TB must be transported outside their
isolation rooms for medically essential procedures that cannot be performed
in the isolation rooms, they should wear surgical masks that cover their
mouths and noses during transport. Persons transporting the patients do not
need to wear respiratory protection outside the TB isolation rooms. Procedures
for these patients should be scheduled at times when they can be performed
rapidly and when waiting areas are less crowded. * Treatment and procedure
rooms in which patients who have infectious TB or who have an undiagnosed
pulmonary disease and are at high risk for active TB receive care should meet
the ventilation recommendations for isolation rooms (Section II.E.3; Suppl. 3).
Ideally, facilities in which TB patients are frequently treated should have
an area in the radiology department that is ventilated separately for TB
patients. If this is not possible, TB patients should wear surgical masks and
should stay in the radiology suite the minimum amount of time possible, then
be returned promptly to their isolation rooms. * The number of persons
entering an isolation room should be minimal. All persons who enter an
isolation room should wear respiratory protection (Section II.G; Suppl. 4).
The patient's visitors should be given respirators to wear while in the
isolation room, and they should be given general instructions on how to use
their respirators. * Disposable items contaminated with respiratory
secretions are not associated with transmission of M. tuberculosis. However,
for general infection-control purposes, these items should be handled and
transported in a manner that reduces the risk for transmitting other
microorganisms to patients, HCWs, and visitors and that decreases
environmental contamination in the health-care facility. Such items should be
disposed of in accordance with hospital policy and applicable regulations
(Suppl. 5). 3. The TB isolation room * TB isolation rooms should be
single-patient rooms with special ventilation characteristics appropriate for
the purposes of isolation (Suppl. 3). The primary purposes of TB isolation
rooms are to a) separate patients who are likely to have infectious TB from
other persons; b) provide an environment that will allow reduction of the
concentration of droplet nuclei through various engineering methods; and c)
prevent the escape of droplet nuclei from the TB isolation room and treatment
room, thus preventing entry of M. tuberculosis into the corridor and other
areas of the facility. * To prevent the escape of droplet nuclei, the TB
isolation room should be maintained under negative pressure (Suppl. 3). Doors
to isolation rooms should be kept closed, except when patients or personnel
must enter or exit the room, so that negative pressure can be maintained. *
Negative pressure in the room should be monitored daily while the room is
being used for TB isolation. * The American Society of Heating, Refrigerating
and Air-Conditioning Engineers, Inc. (ASHRAE) (47), the American Institute of
Architects (AIA) (48), and the Health Resources and Services Administration
(49) recommend a minimum of 6 air changes per hour (ACH) for TB isolation and
treatment rooms. This ventilation rate is based on comfort and odor control
considerations. The effectiveness of this level of airflow in reducing the
concentration of droplet nuclei in the room, thus reducing the transmission
of airborne pathogens, has not been evaluated directly or adequately. Ventilation
rates of greater than 6 ACH are likely to produce an incrementally greater
reduction in the concentration of bacteria in a room than are lower rates
(50-52). However, accurate quantitation of decreases in risk that would
result from specific increases in general ventilation levels has not been
performed and may not be possible. For the purposes of reducing the
concentration of droplet nuclei, TB isolation and treatment rooms in existing
health-care facilities should have an airflow of greater than or equal to 6
ACH. Where feasible, this airflow rate should be increased to greater than or
equal to 12 ACH by adjusting or modifying the ventilation system or by using
auxiliary means (e.g., recirculation of air through fixed HEPA filtration
systems or portable air cleaners) (Suppl. 3, Section II.B.5.a) (53). New
construction or renovation of existing health-care facilities should be
designed so that TB isolation rooms achieve an airflow of greater than or
equal to 12 ACH. * Air from TB isolation rooms and treatment rooms used to
treat patients who have known or suspected infectious TB should be exhausted
to the outside in accordance with applicable federal, state, and local
regulations. The air should not be recirculated into the general ventilation.
In some instances, recirculation of air into the general ventilation system
from such rooms is unavoidable (i.e., in existing facilities in which the
ventilation system or facility configuration makes venting the exhaust to the
outside impossible). In such cases, HEPA filters should be installed in the
exhaust duct leading from the room to the general ventilation system to
remove infectious organisms and particulates the size of droplet nuclei from
the air before it is returned to the general ventilation system (Section
II.F; Suppl. 3). Air from TB isolation and treatment rooms in new or
renovated facilities should not be recirculated into the general ventilation
system. * Although not required, an anteroom may increase the effectiveness
of the isolation room by minimizing the potential escape of droplet nuclei
into the corridor when the door is opened. To work effectively, the anteroom
should have positive air pressure in relation to the isolation room. The
pressure relationship between the anteroom and the corridor may vary
according to ventilation design. * Upper-room air UVGI may be used as an
adjunct to general ventilation in the isolation room (Section II.F; Suppl. 3).
Air in the isolation room may be recirculated within the room through HEPA filters
or UVGI devices to increase the effective ACH and to increase thermal
efficiency. * Health-care facilities should have enough isolation rooms to
appropriately isolate all patients who have suspected or confirmed active TB.
This number should be estimated using the results of the risk assessment of
the health-care facility. Except for minimal- and very low-risk health-care
facilities, all acute-care inpatient facilities should have at least one TB
isolation room (Section II.B). * Grouping isolation rooms together in one
area of the facility may reduce the possibility of transmitting M.
tuberculosis to other patients and may facilitate care of TB patients and the
installation and maintenance of optimal engineering (particularly
ventilation) controls. 4. Discontinuation of TB isolation * TB
isolation can be discontinued if the diagnosis of TB is ruled out. For some
patients, TB can be ruled out when another diagnosis is confirmed. If a
diagnosis of TB cannot be ruled out, the patient should remain in isolation
until a determination has been made that the patient is noninfectious. However,
patients can be discharged from the healthcare facility while still
potentially infectious if appropriate postdischarge arrangements can be
ensured (Section II.E.5). * The length of time required for a TB patient to
become noninfectious after starting anti-TB therapy varies considerably
(Suppl. 1). Isolation should be discontinued only when the patient is on
effective therapy, is improving clinically, and has had three consecutive
negative sputum AFB smears collected on different days. * Hospitalized
patients who have active TB should be monitored for relapse by having sputum
AFB smears examined regularly (e.g., every 2 weeks). Nonadherence to therapy
(i.e., failure to take medications as prescribed) and the presence of
drug-resistant organisms are the two most common reasons why patients remain
infectious despite treatment. These reasons should be considered if a patient
does not respond clinically to therapy within 2-3 weeks. * Continued
isolation throughout the hospitalization should be strongly considered for
patients who have MDR-TB because of the tendency for treatment failure or
relapse (i.e., difficulty in maintaining noninfectiousness) that has been
observed in such cases. 5. Discharge planning * Before a TB patient is
discharged from the health-care facility, the facility's staff and public
health authorities should collaborate to ensure continuation of therapy. Discharge
planning in the health-care facility should include, at a minimum, a) a
confirmed outpatient appointment with the provider who will manage the
patient until the patient is cured, b) sufficient medication to take until
the outpatient appointment, and c) placement into case management (e.g., DOT)
or outreach programs of the public health department. These plans should be
initiated and in place before the patient's discharge. * Patients who may be
infectious at the time of discharge should only be discharged to facilities
that have isolation capability or to their homes. Plans for discharging a
patient who will return home must consider whether all the household members
were infected previously and whether any uninfected household members are at
very high risk for active TB if infected (e.g., children less than 4 years of
age or persons infected with HIV or otherwise severely immunocompromised). If
the household does include such persons, arrangements should be made to
prevent them from being exposed to the TB patient until a determination has
been made that the patient is noninfectious. F. Engineering Control
Recommendations 1. General ventilation This section deals only
with engineering controls for general-use areas of health-care facilities
(e.g., waiting-room areas and emergency departments). Recommendations for
engineering controls for specific areas of the facility (e.g., TB isolation
rooms) are contained in the sections encompassing those areas. Details
regarding ventilation design, evaluation, and supplemental approaches are
described in Supplement 3. * Health-care facilities should either a) include
as part of their staff an engineer or other professional with expertise in
ventilation or b) have this expertise available from a consultant who is an
expert in ventilation engineering and who also has hospital experience. These
persons should work closely with infection-control staff to assist in
controlling airborne infections. * Ventilation system designs in health-care
facilities should meet any applicable federal, state, and local requirements.
* The direction of airflow in health-care facilities should be designed,
constructed, and maintained so that air flows from clean areas to less-clean
areas. * Health-care facilities serving populations that have a high
prevalence of TB may need to supplement the general ventilation or use
additional engineering approaches (i.e., HEPA filtration or UVGI) in
general-use areas where TB patients are likely to go (e.g., waiting-room
areas, emergency departments, and radiology suites). A single-pass,
nonrecirculating system that exhausts air to the outside, a recirculation
system that passes air through HEPA filters before recirculating it to the
general ventilation system, or upper air UVGI may be used in such areas. 2.
Additional engineering control approaches a. HEPA filtration HEPA filters
may be used in a number of ways to reduce or eliminate infectious droplet
nuclei from room air or exhaust (Suppl. 3). These methods include placement
of HEPA filters a) in exhaust ducts discharging air from booths or enclosures
into the surrounding room; b) in ducts or in ceiling- or wall-mounted units,
for recirculation of air within an individual room (fixed recirculation
systems); c) in portable air cleaners; d) in exhaust ducts to remove droplet
nuclei from air being discharged to the outside, either directly or through
ventilation equipment; and e) in ducts discharging air from the TB isolation
room into the general ventilation system. In any application, HEPA filters
should be installed carefully and maintained meticulously to ensure adequate
functioning. The manufacturers of in-room air cleaning equipment should
provide documentation of the HEPA filter efficiency and the efficiency of the
device in lowering room air contaminant levels. b. UVGI For general-use areas
in which the risk for transmission of M. tuberculosis is relatively high,
UVGI lamps may be used as an adjunct to ventilation for reducing the
concentration of infectious droplet nuclei (Suppl. 3), although the
effectiveness of such units has not been evaluated adequately. Ultra-violet
(UV) units can be installed in a room or corridor to irradiate the air in the
upper portion of the room (i.e., upper-room air irradiation), or they can be
installed in ducts to irradiate air passing through the ducts. UV units
installed in ducts should not be substituted for HEPA filters in ducts that
discharge air from TB isolation rooms into the general ventilation system. However,
UV units can be used in ducts that recirculate air back into the same room. To
function properly and decrease hazards to HCWs and others in the health-care
facility, UV lamps should be installed properly and maintained adequately,
which includes the monitoring of irradiance levels. UV tubes should be
changed according to the manufacturer's instructions or when meter readings
indicate tube failure. An employee trained in the use and handling of UV
lamps should be responsible for these measures and for keeping maintenance
records. Applicable safety guidelines should be followed. Caution should be
exercised to protect HCWs, patients, visitors, and others from excessive
exposure to UV radiation. G. Respiratory Protection * Personal
respiratory protection should be used by a) persons entering rooms in which
patients with known or suspected infectious TB are being isolated, b) persons
present during cough-inducing or aerosol-generating procedures performed on
such patients, and c) persons in other settings where administrative and
engineering controls are not likely to protect them from inhaling infectious
airborne droplet nuclei (Suppl. 4). These other settings include transporting
patients who may have infectious TB in emergency transport vehicles and
providing urgent surgical or dental care to patients who may have infectious
TB before a determination has been made that the patient is noninfectious
(Suppl. 1). * Respiratory protective devices used in health-care settings for
protection against M. tuberculosis should meet the following standard
performance criteria: 1. The ability to filter particles 1 um in size in the
unloaded* state with a filter efficiency of greater than or equal to 95%
(i.e., filter leakage of less than or equal to 5%), given flow rates of up to
50 L per minute. __________ *
Some filters become more efficient as they become loaded with dust. Health-care
settings do not have enough dust in the air to load a filter on a respirator.
Therefore, the filter efficiency for respirators used in health-care settings
must be determined in the unloaded state. 2. The ability to be qualitatively or
quantitatively fit tested in a reliable way to obtain a face-seal leakage of
less than or equal to 10% (54,55). 3. The ability to fit the different facial
sizes and characteristics of HCWs, which can usually be met by making the
respirators available in at least three sizes. 4. The ability to be checked
for facepiece fit, in accordance with standards established by the
Occupational Safety and Health Administration (OSHA) and good industrial
hygiene practice, by HCWs each time they put on their respirators (54,55). * The
facility's risk assessment may identify a limited number of selected settings
(e.g., bronchoscopy performed on patients suspected of having TB or autopsy
performed on deceased persons suspected of having had active TB at the time
of death) where the estimated risk for transmission of M. tuberculosis may be
such that a level of respiratory protection exceeding the standard
performance criteria is appropriate. In such circumstances, a level of
respiratory protection exceeding the standard criteria and compatible with
patient-care delivery (e.g., more protective negative-pressure respirators;
powered air-purifying particulate respirators [PAPRs]; or positive-pressure
air-line, half-mask respirators) should be provided by employers to HCWs who
are exposed to M. tuberculosis. Information on these and other respirators is
in the NIOSH Guide to Industrial Respiratory Protection (55) and in
Supplement 4 of this document. * In some settings, HCWs may be at risk for
two types of exposure: a) inhalation of M. tuberculosis and b) mucous
membrane exposure to fluids that may contain bloodborne pathogens. In these
settings, protection against both types of exposure should be used. * When
operative procedures (or other procedures requiring a sterile field) are
performed on patients who may have infectious TB, respiratory protection worn
by the HCW should serve two functions: a) it should protect the surgical
field from the respiratory secretions of the HCW, and b) it should protect
the HCW from infectious droplet nuclei that may be expelled by the patient or
generated by the procedure. Respirators with exhalation valves and most
positive-pressure respirators do not protect the sterile field. * Health-care
facilities in which respiratory protection is used to prevent inhalation of
M. tuberculosis are required by OSHA to develop, implement, and maintain a
respiratory protection program (Suppl. 4). All HCWs who use respiratory
protection should be included in this program. Visitors to TB patients should
be given respirators to wear while in isolation rooms, and they should be
given general instructions on how to use their respirators. * Facilities that
do not have isolation rooms and do not perform cough-inducing procedures on
patients who may have TB may not need to have a respiratory protection
program for TB. However, such facilities should have written protocols for
the early identification of patients who have signs or symptoms of TB and
procedures for referring these patients to a facility where they can be
evaluated and managed appropriately. These protocols should be evaluated
regularly and revised as needed. * Surgical masks are designed to prevent the
respiratory secretions of the person wearing the mask from entering the air. To
reduce the expulsion of droplet nuclei into the air, patients suspected of
having TB should wear surgical masks when not in TB isolation rooms. These
patients do not need to wear particulate respirators, which are designed to
filter the air before it is inhaled by the person wearing the respirator. Patients
suspected of having or known to have TB should never wear a respirator that
has an exhalation valve, because this type of respirator does not prevent
expulsion of droplet nuclei into the air. H. Cough-Inducing and
Aerosol-Generating Procedures 1. General guidelines Procedures
that involve instrumentation of the lower respiratory tract or induce
coughing can increase the likelihood of droplet nuclei being expelled into
the air. These cough-inducing procedures include endotracheal intubation and
suctioning, diagnostic sputum induction, aerosol treatments (e.g.,
pentamidine therapy), and bronchoscopy. Other procedures that can generate
aerosols (e.g., irrigation of tuberculous abscesses, homogenizing or
lyophilizing tissue, or other processing of tissue that may contain tubercle
bacilli) are also covered by these recommendations. * Cough-inducing
procedures should not be performed on patients who may have infectious TB
unless the procedures are absolutely necessary and can be performed with
appropriate precautions. * All cough-inducing procedures performed on
patients who may have infectious TB should be performed using local exhaust
ventilation devices (e.g., booths or special enclosures) or, if this is not
feasible, in a room that meets the ventilation requirements for TB isolation.
* HCWs should wear respiratory protection when present in rooms or enclosures
in which cough-inducing procedures are being performed on patients who may
have infectious TB. * After completion of cough-inducing procedures, patients
who may have infectious TB should remain in their isolation rooms or
enclosures and not return to common waiting areas until coughing subsides. They
should be given tissues and instructed to cover their mouths and noses with
the tissues when coughing. If TB patients must recover from sedatives or
anesthesia after a procedure (e.g, after a bronchoscopy), they should be
placed in separate isolation rooms (and not in recovery rooms with other
patients) while they are being monitored. * Before the booth, enclosure, or
room is used for another patient, enough time should be allowed to pass for
at least 99% of airborne contaminants to be removed. This time will vary
according to the efficiency of the ventilation or filtration used (Suppl. 3,
Table S-31). 2. Special considerations for bronchoscopy * If
performing bronchoscopy in positive-pressure rooms (e.g., operating rooms) is
unavoidable, TB should be ruled out as a diagnosis before the procedure is
performed. If the bronchoscopy is being performed for the purpose of
diagnosing pulmonary disease and that diagnosis could include TB, the
procedure should be performed in a room that meets TB isolation ventilation
requirements. 3. Special considerations for the administration of
aerosolized pentamidine * Patients should be screened for active TB
before prophylactic therapy with aerosolized pentamidine is initiated. Screening
should include obtaining a medical history and performing skin testing and
chest radiography. * Before each subsequent treatment with aerosolized
pentamidine, patients should be screened for symptoms suggestive of TB (e.g.,
development of a productive cough). If such symptoms are elicited, a
diagnostic evaluation for TB should be initiated. * Patients who have
suspected or confirmed active TB should take, if clinically practical, oral
prophylaxis for P. carinii pneumonia. I. Education and Training of HCWs
All HCWs, including physicians, should receive education regarding TB that is
relevant to persons in their particular occupational group. Ideally, training
should be conducted before initial assignment, and the need for additional
training should be reevaluated periodically (e.g., once a year). The level
and detail of this education will vary according to the HCW's work
responsibilities and the level of risk in the facility (or area of the
facility) in which the HCW works. However, the program may include the
following elements: * The basic concepts of M. tuberculosis transmission,
pathogenesis, and diagnosis, including information concerning the difference
between latent TB infection and active TB disease, the signs and symptoms of
TB, and the possibility of reinfection. * The potential for occupational
exposure to persons who have infectious TB in the health-care facility,
including information concerning the prevalence of TB in the community and
facility, the ability of the facility to properly isolate patients who have
active TB, and situations with increased risk for exposure to M.
tuberculosis. * The principles and practices of infection control that reduce
the risk for transmission of M. tuberculosis, including information
concerning the hierarchy of TB infection-control measures and the written
policies and procedures of the facility. Site-specific control measures
should be provided to HCWs working in areas that require control measures in
addition to those of the basic TB infection-control program. * The purpose of
PPD skin testing, the significance of a positive PPD test result, and the
importance of participating in the skin-test program. * The principles of
preventive therapy for latent TB infection. These principles include the
indications, use, effectiveness, and the potential adverse effects of the
drugs (Suppl. 2). * The HCW's responsibility to seek prompt medical
evaluation if a PPD test conversion occurs or if symptoms develop that could
be caused by TB. Medical evaluation will enable HCWs who have TB to receive
appropriate therapy and will help to prevent transmission of M. tuberculosis
to patients and other HCWs. * The principles of drug therapy for active TB. *
The importance of notifying the facility if the HCW is diagnosed with active
TB so that contact investigation procedures can be initiated. * The
responsibilities of the facility to maintain the confidentiality of the HCW
while ensuring that the HCW who has TB receives appropriate therapy and is
noninfectious before returning to duty. * The higher risks associated with TB
infection in persons who have HIV infection or other causes of severely
impaired cell-mediated immunity, including a) the more frequent and rapid
development of clinical TB after infection with M. tuberculosis, b) the
differences in the clinical presentation of disease, and c) the high
mortality rate associated with MDR-TB in such persons. * The potential
development of cutaneous anergy as immune function (as measured by CD4+
T-lymphocyte counts) declines. * Information regarding the efficacy and
safety of BCG vaccination and the principles of PPD screening among BCG
recipients. * The facility's policy on voluntary work reassignment options
for immunocompromised HCWs. J. HCW Counseling, Screening, and Evaluation
* A TB counseling, screening, and prevention program for HCWs should be
established to protect both HCWs and patients. HCWs who have positive PPD test
results, PPD test conversions, or symptoms suggestive of TB should be
identified, evaluated to rule out a diagnosis of active TB, and started on
therapy or preventive therapy if indicated (5). In addition, the results of
the HCW PPD screening program will contribute to evaluation of the
effectiveness of current infection-control practices. 1. Counseling HCWs
regarding TB * Because of the increased risk for rapid progression from
latent TB infection to active TB in HIV-infected or otherwise severely immunocompromised
persons, all HCWs should know if they have a medical condition or are
receiving a medical treatment that may lead to severely impaired
cell-mediated immunity. HCWs who may be at risk for HIV infection should know
their HIV status (i.e., they should be encouraged to voluntarily seek
counseling and testing for HIV antibody status). Existing guidelines for
counseling and testing should be followed routinely (56). Knowledge of these
conditions allows the HCW to seek the appropriate preventive measures
outlined in this document and to consider voluntary work reassignments. Of
particular importance is that HCWs need to know their HIV status if they are
at risk for HIV infection and they work in settings where patients who have
drug-resistant TB may be encountered. * All HCWs should be informed about the
need to follow existing recommendations for infection control to minimize the
risk for exposure to infectious agents; implementation of these
recommendations will greatly reduce the risk for occupational infections
among HCWs (57). All HCWs should also be informed about the potential risks
to severely immunocompromised persons associated with caring for patients who
have some infectious diseases, including TB. It should be emphasized that
limiting exposure to TB patients is the most protective measure that severely
immunosuppressed HCWs can take to avoid becoming infected with M.
tuberculosis. HCWs who have severely impaired cell-mediated immunity and who
may be exposed to M. tuberculosis may consider a change in job setting to
avoid such exposure. HCWs should be advised of the option that severely
immunocompromised HCWs can choose to transfer voluntarily to areas and work
activities in which there is the lowest possible risk for exposure to M.
tuberculosis. This choice should be a personal decision for HCWs after they
have been informed of the risks to their health. * Employers should make
reasonable accommodations (e.g., alternative job assignments) for employees
who have a health condition that compromises cell-mediated immunity and who
work in settings where they may be exposed to M. tuberculosis. HCWs who are
known to be immunocompromised should be referred to employee health
professionals who can individually counsel the employees regarding their risk
for TB. Upon the request of the immunocompromised HCW, employers should
offer, but not compel, a work setting in which the HCW would have the lowest
possible risk for occupational exposure to M. tuberculosis. Evaluation of
these situations should also include consideration of the provisions of the
Americans With Disabilities Act of 1990* and other applicable federal, state,
and local laws. __________ *
Americans With Disabilities Act of 1990. PL 101-336, 42 U.S.C. 12101 et seq. * All HCWs should be informed that
immunosuppressed HCWs should have appropriate follow-up and screening for
infectious diseases, including TB, provided by their medical practitioner. HCWs
who are known to be HIV-infected or otherwise severely immunosuppressed
should be tested for cutaneous anergy at the time of PPD testing (Suppl. 2).
Consideration should be given to retesting, at least every 6 months, those
immunocompromised HCWs who are potentially exposed to M. tuberculosis because
of the high risk for rapid progression to active TB if they become infected. *
Information provided by HCWs regarding their immune status should be treated
confidentially. If the HCW requests voluntary job reassignment, the
confidentiality of the HCW should be maintained. Facilities should have
written procedures on confidential handling of such information. 2.
Screening HCWs for active TB * Any HCW who has a persistent cough (i.e.,
a cough lasting greater than or equal to 3 weeks), especially in the presence
of other signs or symptoms compatible with active TB (e.g., weight loss,
night sweats, bloody sputum, anorexia, or fever), should be evaluated
promptly for TB. The HCW should not return to the workplace until a diagnosis
of TB has been excluded or until the HCW is on therapy and a determination
has been made that the HCW is noninfectious. 3. Screening HCWs for latent TB infection * The risk assessment should identify which
HCWs have potential for exposure to M. tuberculosis and the frequency with
which the exposure may occur. This information is used to determine which
HCWs to include in the skin-testing program and the frequency with which they
should be Table 2). * If HCWs are from risks groups with increased prevalence
of TB, consideration may be given to including them in the skin-testing
program, even if they do not have potential occupational exposure to M.
tuberculosis, so that converters can be identified and preventive therapy
offered. * Administrators of health-care facilities should ensure that
physicians and other personnel not paid by, but working in, the facility
receive skin testing at appropriate intervals for their occupational group
and work location. * During the pre-employment physical or when applying for
hospital privileges, HCWs who have potential for exposure to M. tuberculosis
(Table 2), including those with a history of BCG vaccination, should have
baseline PPD skin testing performed (Suppl. 2). For HCWs who have not had a
documented negative PPD test result during the preceding 12 months, the
baseline PPD testing should employ the two-step method; this will detect
boosting phenomena that might be misinterpreted as a skin-test conversion. Decisions
concerning the use of the two-step procedure for baseline testing in a
particular facility should be based on the frequency of boosting in that
facility. * HCWs who have a documented history of a positive PPD test,
adequate treatment for disease, or adequate preventive therapy for infection,
should be exempt from further PPD screening unless they develop signs or
symptoms suggestive of TB. * PPD-negative HCWs should undergo repeat PPD
testing at regular intervals as determined by the risk assessment (Section
II.B). In addition, these HCWs should be tested whenever they have been
exposed to a TB patient and appropriate precautions were not observed at the
time of exposure (Section II.K.3). Performing PPD testing of HCWs who work in
the same area or occupational group on different scheduled dates (e.g., test
them on their birthdays or on their employment anniversary dates), rather
than testing all HCWs in the area or group on the same day, may lead to
earlier detection of M. tuberculosis transmission. * All PPD tests should be
administered, read, and interpreted in accordance with current guidelines by
specified trained personnel (Suppl. 2). At the time their test results are
read, HCWs should be informed about the interpretation of both positive and
negative PPD test results. This information should indicate that the
interpretation of an induration that is 5-9 mm in diameter depends on the
HCW's immune status and history of exposure to persons who have infectious
TB. Specifically, HCWs who have indurations of 5-9 mm in diameter should be
advised that such results may be considered positive for HCWs who are
contacts of persons with infectious TB or who have HIV infection or other
causes of severe immunosuppression (e.g., immunosuppressive therapy for organ
transplantation). * When an HCW who is not assigned regularly to a single
work area has a PPD test conversion, appropriate personnel should identify
the areas where the HCW worked during the time when infection was likely to
have occurred. This information can then be considered in analyzing the risk
for transmission in those areas. * In any area of the facility where
transmission of M. tuberculosis is known to have occurred, a problem
evaluation should be conducted (Section II.K), and the frequency of skin
testing should be determined according to the applicable risk category
(Section II.B). * PPD test results should be recorded confidentially in the
individual HCW's employee health record and in an aggregate database of all
HCW PPD test results. The database can be analyzed periodically to estimate
the risk for acquiring new infection in specific areas or occupational groups
in the facility. 4. Evaluation and management of HCWs who have positive
PPD test results or active TB a. Evaluation * All HCWs with newly
recognized positive PPD test results or PPD test conversions should be
evaluated promptly for active TB. This evaluation should include a clinical
examination and a chest radiograph. If the history, clinical examination, or
chest radiograph is compatible with active TB, additional tests should be
performed (Section II.C.2). If symptoms compatible with TB are present, the
HCW should be excluded from the workplace until either a) a diagnosis of
active TB is ruled out or b) a diagnosis of active TB was established, the
HCW is being treated, and a determination has been made that the HCW is
noninfectious (Suppl. 2). HCWs who do not have active TB should be evaluated
for preventive therapy according to published guidelines (Suppl. 2). * If an
HCW's PPD test result converts to positive, a history of confirmed or
suspected TB exposure should be obtained in an attempt to determine the
potential source. When the source of exposure is known, the
drug-susceptibility pattern of the M. tuberculosis isolated from the source
should be identified so that the correct curative or preventive therapy can
be initiated for the HCW with the PPD test conversion. The
drug-susceptibility pattern should be recorded in the HCW's medical record,
where it will be available if the HCW subsequently develops active TB and
needs therapy specific for the drug-susceptibility pattern. * All HCWs,
including those with histories of positive PPD test results, should be
reminded periodically about the symptoms of TB and the need for prompt
evaluation of any pulmonary symptoms suggestive of TB. b. Routine and follow-up chest radiographs * Routine chest radiographs are not required
for asymptomatic, PPD-negative HCWs. HCWs with positive PPD test results
should have a chest radiograph as part of the initial evaluation of their PPD
test; if negative, repeat chest radiographs are not needed unless symptoms
develop that could be attributed to TB (58). However, more frequent
monitoring for symptoms of TB may be considered for recent converters and
other PPD-positive HCWs who are at increased risk for developing active TB
(e.g., HIV-infected or otherwise severely immunocompromised HCWs). c. Workplace
restrictions 1) Active TB * HCWs with pulmonary or laryngeal TB pose a risk
to patients and other HCWs while they are infectious, and they should be
excluded from the workplace until they are noninfectious. The same work
restrictions apply to all HCWs regardless of their immune status. * Before
the HCW who has TB can return to the work-place, the health-care facility
should have documentation from the HCW's health-care provider that the HCW is
receiving adequate therapy, the cough has resolved, and the HCW has had three
consecutive negative sputum smears collected on different days. After work
duties are resumed and while the HCW remains on anti-TB therapy, facility
staff should receive periodic documentation from the HCW's health-care
provider that the HCW is being maintained on effective drug therapy for the
recommended time period and that the sputum AFB smears continue to be
negative. * HCWs with active laryngeal or pulmonary TB who discontinue
treatment before they are cured should be evaluated promptly for
infectiousness. If the evaluation determines that they are still infectious,
they should be excluded from the workplace until treatment has been resumed,
an adequate response to therapy has been documented, and three more
consecutive sputum AFB smears collected on different days have been negative.
* HCWs who have TB at sites other than the lung or larynx usually do not need
to be excluded from the workplace if a diagnosis of concurrent pulmonary TB
has been ruled out. 2) Latent TB infection * HCWs receiving preventive treatment for
latent TB infection should not be restricted from their usual work
activities. * HCWs with latent TB infection who cannot take or who do not
accept or complete a full course of preventive therapy should not be excluded
from the work-place. These HCWs should be counseled about the risk for
developing active TB and instructed regularly to seek prompt evaluation if
signs or symptoms develop that could be caused by TB. K. Problem
Evaluation Epidemiologic investigations may be indicated for several
situations. These include, but are not limited to, a) the occurrence of PPD
test conversions or active TB in HCWs; b) the occurrence of possible
person-to-person transmission of M. tuberculosis; and c) situations in which
patients or HCWs with active TB are not promptly identified and isolated,
thus exposing other persons in the facility to M. tuberculosis. The general
objectives of the epidemiologic investigations in these situations are as
follows: 1) to determine the likelihood that transmission of and infection
with M. tuberculosis has occurred in the facility; 2) to determine the extent
to which M. tuberculosis has been transmitted; 3) to identify those persons
who have been exposed and infected, enabling them to receive appropriate
clinical management; 4) to identify factors that could have contributed to
transmission and infection and to implement appropriate interventions; and 5)
to evaluate the effectiveness of any interventions that are implemented and
to ensure that exposure to and transmission of M. tuberculosis have been
terminated. The exact circumstances of these situations are likely to vary
considerably, and the associated epidemiologic investigations should be
tailored to the individual circumstances. The following sections provide
general guidance for conducting these investigations. 1. Investigating PPD
test conversions and active TB in HCWs a. Investigating PPD test conversions in HCWs PPD test conversions may be detected in HCWs
as a result of a contact investigation, in which case the probable source of
exposure and transmission is already known (Section II.K.3.), or as a result
of routine screening, in which case the probable source of exposure and
infection is not already known and may not be immediately apparent. If a
skin-test conversion in an HCW is identified as part of routine screening,
the following steps should be considered (Figure 2): * The HCW should be
evaluated promptly for active TB. The initial evaluation should include a
thorough history, physical examination, and chest radiograph. On the basis of
the initial evaluation, other diagnostic procedures (e.g., sputum
examination) may be indicated. * If appropriate, the HCW should be placed on
preventive or curative therapy in accordance with current guidelines (Suppl. 2)
(5). * A history of possible exposure to M. tuberculosis should be obtained
from the HCW to determine the most likely source of infection. When the
source of infection is known, the drug-susceptibility pattern of the M.
tuberculosis isolate from the source patient should be identified to
determine appropriate preventive or curative therapy regimens. * If the
history suggests that the HCW was exposed to and infected with M.
tuberculosis outside the facility, no further epidemiologic investigation to
identify a source in the facility is necessary. * If the history does not
suggest that the HCW was exposed and infected outside the facility but does
identify a probable source of exposure in the facility, contacts of the
suspected source patient should be identified and evaluated. Possible reasons
for the exposure and transmission should be evaluated (Table 4),
interventions should be implemented to correct these causes, and PPD testing
of PPD-negative HCWs should be performed immediately and repeated after 3
months. If no additional PPD test conversions are detected on follow-up
testing, the investigation can be terminated. If additional PPD test
conversions are detected on follow-up testing, the possible reasons for
exposure and transmission should be reassessed, the appropriateness of and
degree of adherence to the interventions implemented should be evaluated, and
PPD testing of PPD-negative HCWs should be repeated after another 3 months. If
no additional PPD test conversions are detected on the second round of
follow-up testing, the investigation can be terminated. However, if
additional PPD conversions are detected on the second round of follow-up
testing, a high-risk protocol should be implemented in the affected area or
occupational group, and the public health department or other persons with
expertise in TB infection control should be consulted. * If the history does
not suggest that the HCW was exposed to and infected with M. tuberculosis
outside the facility and does not identify a probable source of exposure in
the facility, further investigation to identify the probable source patient
in the facility is warranted. The interval during which the HCW could have
been infected should be estimated. Generally, this would be the interval from
10 weeks before the most recent negative PPD test through 2 weeks before the
first positive PPD test (i.e., the conversion). Laboratory and
infection-control records should be reviewed to identify all patients or HCWs
who have suspected or confirmed infectious TB and who could have transmitted
M. tuberculosis to the HCW. If this process does identify a likely source
patient, contacts of the suspected source patient should be identified and
evaluated, and possible reasons for the exposure and transmission should be
evaluated (Table 4). Interventions should be implemented to correct these
causes, and PPD testing of PPD-negative HCWs should be repeated after 3
months. However, if this process does not identify a probable source case,
PPD screening results of other HCWs in the same area or occupational group
should be reviewed for additional evidence of M. tuberculosis transmission. If
sufficient additional PPD screening results are not available, appropriate
personnel should consider conducting additional PPD screening of other HCWs
in the same area or occupational group. (For Figure 2, see printed copy) (For Table 4, see printed copy) If this review and/or screening does not
identify additional PPD conversions, nosocomial transmission is less likely,
and the contact investigation can probably be terminated. Whether the HCW's
PPD test conversion resulted from occupational exposure and infection is
uncertain; however, the absence of other data implicating nosocomial
transmission suggests that the conversion could have resulted from a)
unrecognized exposure to M. tuberculosis outside the facility; b)
cross-reactivity with another antigen (e.g., nontuberculous mycobacteria); c)
errors in applying, reading, or interpreting the test; d) false positivity
caused by the normal variability of the test; or e) false positivity caused
by a defective PPD preparation. If this review and/or screening does identify
additional PPD test conversions, nosocomial transmission is more likely. In
this situation, the patient identification (i.e., triage) process, TB
infection-control policies and practices, and engineering controls should be
evaluated to identify problems that could have led to exposure and
transmission (Table 4). If no such problems are identified, a high-risk
protocol should be implemented in the affected area or occupational group,
and the public health department or other persons with expertise in TB
infection control should be consulted. If such problems are identified,
appropriate interventions should be implemented to correct the problem(s),
and PPD skin testing of PPD-negative HCWs should be repeated after 3 months. If
no additional PPD conversions are detected on follow-up testing, the
investigation can be terminated. If additional PPD conversions are detected
on follow-up testing, the possible reasons for exposure and transmission
should be reassessed, the appropriateness of and adherence to the
interventions implemented should be evaluated, and PPD skin testing of
PPD-negative HCWs should be repeated after another 3 months. If no additional
PPD test conversions are detected on this second round of follow-up testing,
the investigation can be terminated. However, if additional PPD test
conversions are detected on the second round of follow-up testing, a
high-risk protocol should be implemented in the affected area or occupational
group, and the public health department or other persons with expertise in TB
infection control should be consulted. b. Investigating cases of active TB in HCWs If an HCW develops active TB, the following
steps should be taken: * The case should be evaluated epidemiologically, in a
manner similar to PPD test conversions in HCWs, to determine the likelihood
that it resulted from occupational transmission and to identify possible
causes and implement appropriate interventions if the evaluation suggests
such transmission. * Contacts of the HCW (e.g., other HCWs, patients,
visitors, and others who have had intense exposure to the HCW) should be
identified and evaluated for TB infection and disease (Section II.K.3; Suppl.
2). The public health department should be notified immediately for
consultation and to allow for investigation of community contacts who were
not exposed in the health-care facility. * The public health department
should notify facilities when HCWs with TB are reported by physicians so that
an investigation of contacts can be conducted in the facility. The
information provided by the health department to facilities should be in
accordance with state or local laws to protect the confidentiality of the
HCW. 2. Investigating possible patient-to-patient transmission of M.
tuberculosis Surveillance of active TB cases in patients should be
conducted. If this surveillance suggests the possibility of patient-to-patient
transmission of M. tuberculosis (e.g., a high proportion of TB patients had
prior admissions during the year preceding onset of their TB, the number of
patients with drug-resistant TB increased suddenly, or isolates obtained from
multiple patients had identical and characteristic drug-susceptibility or DNA
fingerprint patterns), the following steps should be taken: * Review the HCW
PPD test results and patient surveillance data for the suspected areas to
detect additional patients or HCWs with PPD test conversions or active
disease. * Look for possible exposures that patients with newly diagnosed TB
could have had to other TB patients during previous admissions. For example,
were the patients admitted to the same room or area, or did they receive the
same procedure or go to the same treatment area on the same day? If the
evaluation thus far suggests transmission has occurred, the following steps
should be taken: * Evaluate possible causes of the transmission (e.g.,
problem with patient detection, institutional barriers to implementing
appropriate isolation practices, or inadequate engineering controls) (Table
4). * Ascertain whether other patients or HCWs could have been exposed; if
so, evaluate these persons for TB infection and disease (Section II.K.3;
Suppl. 2). * Notify the public health department so they can begin a
community contact investigation if necessary. 3. Investigating contacts of
patients and HCWs who have infectious TB If a patient who has active TB
is examined in a health-care facility and the illness is not diagnosed
correctly, resulting in failure to apply appropriate precautions, or if an
HCW develops active TB and exposes other persons in the facility, the
following steps should be taken when the illness is later diagnosed correctly:
* To identify other patients and HCWs who were exposed to the source patient
before isolation procedures were begun, interview the source patient and all
applicable personnel and review that patient's medical record. Determine the
areas of the facility in which the source patient was hospitalized, visited,
or worked before being placed in isolation (e.g., outpatient clinics,
hospital rooms, treatment rooms, radiology and procedure areas, and patient
lounges) and the HCWs who may have been exposed during that time (e.g.,
persons providing direct care, therapists, clerks, transportation personnel,
housekeepers, and social workers). * The contact investigation should first
determine if M. tuberculosis transmission has occurred from the source
patient to those persons with whom the source patient had the most intense
contact. * Administer PPD tests to the most intensely exposed HCWs and
patients as soon as possible after the exposure has occurred. If transmission
did occur to the most intensely exposed persons, then those persons with whom
the patient had less contact should be evaluated. If the initial PPD test
result is negative, a second test should be administered 12 weeks after the
exposure was terminated. * Those persons who were exposed to M. tuberculosis
and who have either a PPD test conversion or symptoms suggestive of TB should
receive prompt clinical evaluation and, if indicated, chest radiographs and
bacteriologic studies should be performed (Suppl. 2). Those persons who have
evidence of newly acquired infection or active disease should be evaluated
for preventive or curative therapy (Suppl. 2). Persons who have previously
had positive PPD test results and who have been exposed to an infectious TB
patient do not require a repeat PPD test or a chest radiograph unless they
have symptoms suggestive of TB. * In addition to PPD testing those HCWs and
patients who have been exposed to M. tuberculosis because a patient was not
isolated promptly or an HCW with active TB was not identified promptly, the
investigation should determine why the diagnosis of TB was delayed. If the
correct diagnosis was made but the patient was not isolated promptly, the
reasons for the delay need to be defined so that corrective actions can be
taken. L. Coordination with the Public Health Department * As soon as
a patient or HCW is known or suspected to have active TB, the patient or HCW
should be reported to the public health department so that appropriate
follow-up can be arranged and a community contact investigation can be performed.
The health department should be notified well before patient discharge to
facilitate follow-up and continuation of therapy. A discharge plan
coordinated with the patient or HCW, the health department, and the inpatient
facility should be implemented. * The public health department should protect
the confidentiality of the patient or HCW in accordance with state and local
laws. * Health-care facilities and health departments should coordinate their
efforts to perform appropriate contact investigations on patients and HCWs
who have active TB. * In accordance with state and local laws and
regulations, results of all AFB-positive sputum smears, cultures positive for
M. tuberculosis, and drug-susceptibility results on M. tuberculosis isolates
should be reported to the public health department as soon as these results
are available. * The public health department may be able to assist
facilities with planning and implementing various aspects of a TB
infection-control program (e.g., surveillance, screening activities, and
outbreak investigations). In addition, the state health department may be
able to provide names of experts to assist with the engineering aspects of TB
infection control. M. Additional Considerations for Selected Areas in
Health-Care Facilities and Other Health-Care Settings This section
contains additional information for selected areas in health-care facilities
and for other health-care settings. 1. Selected areas in health-care
facilities a. Operating rooms * Elective operative procedures on patients
who have TB should be delayed until the patient is no longer infectious. * If
operative procedures must be performed, they should be done, if possible, in
operating rooms that have anterooms. For operating rooms without anterooms,
the doors to the operating room should be closed, and traffic into and out of
the room should be minimal to reduce the frequency of opening and closing the
door. Attempts should be made to perform the procedure at a time when other
patients are not present in the operative suite and when a minimum number of
personnel are present (e.g., at the end of day). * Placing a bacterial filter
on the patient endotracheal tube (or at the expiratory side of the breathing
circuit of a ventilator or anesthesia machine if these are used) when
operating on a patient who has confirmed or suspected TB may help reduce the
risk for contaminating anesthesia equipment or discharging tubercle bacilli
into the ambient air. * During postoperative recovery, the patient should be
monitored and should be placed in a private room that meets recommended
standards for ventilating TB isolation rooms. * When operative procedures (or
other procedures requiring a sterile field) are performed on patients who may
have infectious TB, respiratory protection worn by the HCW must protect the
field from the respiratory secretions of the HCW and protect the HCW from the
infectious droplet nuclei generated by the patient. Valved or
positive-pressure respirators do not protect the sterile field; therefore, a
respirator that does not have a valve and that meets the criteria in Section
II.G should be used. b. Autopsy rooms * Because infectious aerosols are
likely to be present in autopsy rooms, such areas should be at negative
pressure with respect to adjacent areas (Suppl. 3), and the room air should
be exhausted directly to the outside of the building. ASHRAE recommends that
autopsy rooms have ventilation that provides an airflow of 12 ACH (47),
although the effectiveness of this ventilation level in reducing the risk for
M. tuberculosis transmission has not been evaluated. Where possible, this
level should be increased by means of ventilation system design or by
auxiliary methods (e.g., recirculation of air within the room through HEPA
filters) (Suppl. 3). * Respiratory protection should be worn by personnel
while performing autopsies on deceased persons who may have had TB at the
time of death (Section II.G; Suppl. 4). * Recirculation of HEPA-filtered air
within the room or UVGI may be used as a supplement to the recommended
ventilation (Suppl. 3). c. Laboratories * Laboratories in which specimens for
mycobacteriologic studies (e.g., AFB smears and cultures) are processed
should be designed to conform with criteria specified by CDC and the National
Institutes of Health (59). 2. Other health-care settings TB precautions may
be appropriate in a number of other types of health-care settings. The
specific precautions that are applied will vary depending on the setting. At
a minimum, a risk assessment should be performed yearly for these settings; a
written TB infection-control plan should be developed, evaluated, and revised
on a regular basis; protocols should be in place for identifying and managing
patients who may have active TB; HCWs should receive appropriate training, education,
and screening; protocols for problem evaluation should be in place; and
coordination with the public health department should be arranged when
necessary. Other recommendations specific to certain of these settings
follow. a. Emergency medical services * When EMS personnel or others must
transport patients who have confirmed or suspected active TB, a surgical mask
should be placed, if possible, over the patient's mouth and nose. Because
administrative and engineering controls during emergency transport situations
cannot be ensured, EMS personnel should wear respiratory protection when
transporting such patients. If feasible, the windows of the vehicle should be
kept open. The heating and air-conditioning system should be set on a
nonrecirculating cycle. * EMS personnel should be included in a comprehensive
PPD screening program and should receive a baseline PPD test and follow-up
testing as indicated by the risk assessment. They should also be included in
the follow-up of contacts of a patient with infectious TB.* __________ *
The Ryan White Comprehensive AIDS Resource Emergency Act of 1990, P.L.
101-381, mandates notification of EMS personnel after they have been exposed
to infectious pulmonary TB (42 U.S.C. 300ff-82.54 Fed. Reg. 13417 [March 21,
1994]). b. Hospices * Hospice patients who have
confirmed or suspected TB should be managed in the manner described in this
document for management of TB patients in hospitals. General-use and
specialized areas (e.g., treatment or TB isolation rooms) should be
ventilated in the same manner as described for similar hospital areas. c.
Long-term care facilities * Recommendations published previously for
preventing and controlling TB in long-term care facilities should be followed
(60). * Long-term care facilities should also follow the recommendations
outlined in this document. d. Correctional facilities * Recommendations
published previously for preventing and controlling TB in correctional
facilities should be followed (61). * Prison medical facilities should also
follow the recommendations outlined in this document. e. Dental settings In
general, the symptoms for which patients seek treatment in a dental-care
setting are not likely to be caused by infectious TB. Unless a patient
requiring dental care coincidentally has TB, it is unlikely that infectious
TB will be encountered in the dental setting. Furthermore, generation of
droplet nuclei containing M. tuberculosis during dental procedures has not
been demonstrated (62). Therefore, the risk for transmission of M.
tuberculosis in most dental settings is probably quite low. Nevertheless,
during dental procedures, patients and dental workers share the same air for
varying periods of time. Coughing may be stimulated occasionally by oral
manipulations, although no specific dental procedures have been classified as
"cough-inducing." In some instances, the population served by a
dental-care facility, or the HCWs in the facility, may be at relatively high
risk for TB. Because the potential exists for transmission of M. tuberculosis
in dental settings, the following recommendations should be followed: * A
risk assessment (Section II.B) should be done periodically, and TB
infection-control policies for each dental setting should be based on the
risk assessment. The policies should include provisions for detection and
referral of patients who may have undiagnosed active TB; management of
patients with active TB, relative to provision of urgent dental care; and
employer-sponsored HCW education, counseling, and screening. * While taking
patients' initial medical histories and at periodic updates, dental HCWs
should routinely ask all patients whether they have a history of TB disease
and symptoms suggestive of TB. * Patients with a medical history or symptoms
suggestive of undiagnosed active TB should be referred promptly for medical
evaluation of possible infectiousness. Such patients should not remain in the
dental-care facility any longer than required to arrange a referral. While in
the dental-care facility, they should wear surgical masks and should be
instructed to cover their mouths and noses when coughing or sneezing. *
Elective dental treatment should be deferred until a physician confirms that
the patient does not have infectious TB. If the patient is diagnosed as
having active TB, elective dental treatment should be deferred until the
patient is no longer infectious. * If urgent dental care must be provided for
a patient who has, or is strongly suspected of having, infectious TB, such
care should be provided in facilities that can provide TB isolation (Sections
II.E and G). Dental HCWs should use respiratory protection while performing
procedures on such patients. * Any dental HCW who has a persistent cough
(i.e., a cough lasting greater than or equal to 3 weeks), especially in the
presence of other signs or symptoms compatible with active TB (e.g., weight
loss, night sweats, bloody sputum, anorexia, and fever), should be evaluated
promptly for TB. The HCW should not return to the work-place until a
diagnosis of TB has been excluded or until the HCW is on therapy and a
determination has been made that the HCW is noninfectious. * In dental-care
facilities that provide care to populations at high risk for active TB, it
may be appropriate to use engineering controls similar to those used in
general-use areas (e.g., waiting rooms) of medical facilities that have a
similar risk profile. f. Home-health-care settings * HCWs who provide medical
services in the homes of patients who have suspected or confirmed infectious
TB should instruct such patients to cover their mouths and noses with a
tissue when coughing or sneezing. Until such patients are no longer
infectious, HCWs should wear respiratory protection when entering these
patients' homes (Suppl. 4). * Precautions in the home may be discontinued
when the patient is no longer infectious (Suppl. 1). * HCWs who provide
health-care services in their patients' homes can assist in preventing
transmission of M. tuberculosis by educating their patients regarding the
importance of taking medications as prescribed and by administering DOT. *
Cough-inducing procedures performed on patients who have infectious TB should
not be done in the patients' homes unless absolutely necessary. When
medically necessary cough-inducing procedures (e.g., AFB sputum collection
for evaluation of therapy) must be performed on patients who may have
infectious TB, the procedures should be performed in a health-care facility
in a room or booth that has the recommended ventilation for such procedures. If
these procedures must be performed in a patient's home, they should be
performed in a well-ventilated area away from other household members. If
feasible, the HCW should consider opening a window to improve ventilation or
collecting the specimen while outside the dwelling. The HCW collecting these
specimens should wear respiratory protection during the procedure (Section
II.G). * HCWs who provide medical services in their patients' homes should be
included in comprehensive employer-sponsored TB training, education, counseling,
and screening programs. These programs should include provisions for
identifying HCWs who have active TB, baseline PPD skin testing, and follow-up
PPD testing at intervals appropriate to the degree of risk. * Patients who
are at risk for developing active TB and the HCWs who provide medical
services in the homes of such patients should be reminded periodically of the
importance of having pulmonary symptoms evaluated promptly to permit early
detection of and treatment for TB. g. Medical offices In general, the
symptoms of active TB are symptoms for which patients are likely to seek
treatment in a medical office. Furthermore, the populations served by some
medical offices, or the HCWs in the office, may be at relatively high risk
for TB. Thus, it is likely that infectious TB will be encountered in a
medical office. Because of the potential for M. tuberculosis transmission,
the following recommendations should be observed: * A risk assessment should
be conducted periodically, and TB infection-control policies based on results
of the risk assessment should be developed for the medical office. The
policies should include provisions for identifying and managing patients who
may have undiagnosed active TB; managing patients who have active TB; and
educating, training, counseling, and screening HCWs. * While taking patients'
initial medical histories and at periodic updates, HCWs who work in medical
offices should routinely ask all patients whether they have a history of TB
disease or have had symptoms suggestive of TB. * Patients with a medical
history and symptoms suggestive of active TB should receive an appropriate
diagnostic evaluation for TB and be evaluated promptly for possible
infectiousness. Ideally, this evaluation should be done in a facility that has
TB isolation capability. At a minimum, the patient should be provided with
and asked to wear a surgical mask, instructed to cover the mouth and nose
with a tissue when coughing or sneezing, and separated as much as possible
from other patients. * Medical offices that provide evaluation or treatment
services for TB patients should follow the recommendations for managing
patients in ambulatory-care settings (Section II.D). * If cough-inducing
procedures are to be administered in a medical office to patients who may
have active TB, appropriate precautions should be followed (Section II.H). *
Any HCW who has a persistent cough (i.e., a cough lasting greater than or
equal to 3 weeks), especially in the presence of other signs or symptoms
compatible with active TB (e.g., weight loss, night sweats, bloody sputum,
anorexia, or fever) should be evaluated promptly for TB. HCWs with such signs
or symptoms should not return to the workplace until a diagnosis of TB has
been excluded or until they are on therapy and a determination has been made
that they are noninfectious. * HCWs who work in medical offices in which
there is a likelihood of exposure to patients who have infectious TB should
be included in employer-sponsored education, training, counseling, and PPD
testing programs appropriate to the level of risk in the office. * In medical
offices that provide care to populations at relatively high risk for active
TB, use of engineering controls as described in this document for general-use
areas (e.g., waiting rooms) may be appropriate (Section II.F; Suppl. 3). Supplement 1: Determining the Infectiousness of a TB Patient The
infectiousness of patients with TB correlates with the number of organisms
expelled into the air, which, in turn, correlates with the following factors:
a) disease in the lungs, airways, or larynx; b) presence of cough or other
forceful expiratory measures; c) presence of acid-fast bacilli (AFB) in the
sputum; d) failure of the patient to cover the mouth and nose when coughing;
e) presence of cavitation on chest radiograph; f) inappropriate or short
duration of chemotherapy; and g) administration of procedures that can induce
coughing or cause aerosolization of M. tuberculosis (e.g., sputum induction). The
most infectious persons are most likely those who have not been treated for
TB and who have either a) pulmonary or laryngeal TB and a cough or are
undergoing cough-inducing procedures, b) a positive AFB sputum smear, or c)
cavitation on chest radiograph. Persons with extrapulmonary TB usually are
not infectious unless they have a) concomitant pulmonary disease; b)
nonpulmonary disease located in the respiratory tract or oral cavity; or c)
extrapulmonary disease that includes an open abscess or lesion in which the
concentration of organisms is high, especially if drainage from the abscess
or lesion is extensive (20,22). Coinfection with HIV does not appear to
affect the infectiousness of TB patients (63-65). In
general, children who have TB may be less likely than adults to be
infectious; however, transmission from children can occur. Therefore,
children with TB should be evaluated for infectiousness using the same
parameters as for adults (i.e., pulmonary or laryngeal TB, presence of cough
or cough-inducing procedures, positive sputum AFB smear, cavitation on chest
radiograph, and adequacy and duration of therapy). Pediatric patients who may
be infectious include those who a) are not on therapy, b) have just been
started on therapy, or c) are on inadequate therapy, and who a) have
laryngeal or extensive pulmonary involvement, b) have pronounced cough or are
undergoing cough-inducing procedures, c) have positive sputum AFB smears, or
d) have cavitary TB. Children who have typical primary tuberculous lesions
and do not have any of the indicators of infectiousness listed previously
usually do not need to be placed in isolation. Because the source case for
pediatric TB patients often occurs in a member of the infected child's family
(45), parents and other visitors of all pediatric TB patients should be evaluated
for TB as soon as possible. Infection
is most likely to result from exposure to persons who have unsuspected
pulmonary TB and are not receiving anti-TB therapy or from persons who have
diagnosed TB and are not receiving adequate therapy. Administration of
effective anti-TB therapy has been associated with decreased infectiousness
among persons who have active TB (66). Effective therapy reduces coughing,
the amount of sputum produced, and the number of organisms in the sputum. However,
the period of time a patient must take effective therapy before becoming
noninfectious varies between patients (67). For example, some TB patients are
never infectious, whereas those with unrecognized or inadequately treated
drug-resistant TB may remain infectious for weeks or months (24). Thus,
decisions about infectiousness should be made on an individual basis. In
general, patients who have suspected or confirmed active TB should be
considered infectious if they a) are coughing, b) are undergoing
cough-inducing procedures, or c) have positive AFB sputum smears, and if they
a) are not on chemotherapy, b) have just started chemotherapy, or c) have a
poor clinical or bacteriologic response to chemotherapy. A patient who has
drug-susceptible TB and who is on adequate chemotherapy and has had a
significant clinical and bacteriologic response to therapy (i.e., reduction
in cough, resolution of fever, and progressively decreasing quantity of
bacilli on smear) is probably no longer infectious. However, because
drug-susceptibility results are not usually known when the decision to
discontinue isolation is made, all TB patients should remain in isolation
while hospitalized until they have had three consecutive negative sputum
smears collected on different days and they demonstrate clinical improvement. Supplement 2: Diagnosis and Treatment of Latent TB Infection and
Active TB I. Diagnostic Procedures for TB Infection and Disease A diagnosis of TB may be considered for any
patient who has a persistent cough (i.e., a cough lasting greater than or
equal to 3 weeks) or other signs or symptoms compatible with TB (e.g., bloody
sputum, night sweats, weight loss, anorexia, or fever). However, the index of
suspicion for TB will vary in different geographic areas and will depend on
the prevalence of TB and other characteristics of the population served by
the facility. The index of suspicion for TB should be very high in areas or
among groups of patients in which the prevalence of TB is high (Section I.B).
Persons for whom a diagnosis of TB is being considered should receive
appropriate diagnostic tests, which may include PPD skin testing, chest
radiography, and bacteriologic studies (e.g., sputum microscopy and culture).
A. PPD Skin Testing and Anergy Testing 1. Application and reading of
PPD skin tests The PPD skin test is the only method available for
demonstrating infection with M. tuberculosis. Although currently available
PPD tests are less than 100% sensitive and specific for detection of
infection with M. tuberculosis, no better diagnostic methods have yet been
devised. Interpretation of PPD test results requires knowledge of the antigen
used, the immunologic basis for the reaction to this antigen, the technique
used to administer and read the test, and the results of epidemiologic and
clinical experience with the test (2,5,6). The PPD test, like all medical
tests, is subject to variability, but many of the variations in administering
and reading PPD tests can be avoided by proper training and careful attention
to details. The intracutaneous (Mantoux) administration of a measured amount
of PPD-tuberculin is currently the preferred method for doing the test. One-tenth
milliliter of PPD (5 TU) is injected just beneath the surface of the skin on
either the volar or dorsal surface of the forearm. A discrete, pale elevation
of the skin (i.e., a wheal) that is 6-10 mm in diameter should be produced. PPD
test results should be read by designated, trained personnel between 48 and
72 hours after injection. Patient or HCW self-reading of PPD test results
should not be accepted (68). The result of the test is based on the presence
or absence of an induration at the injection site. Redness or erythema should
not be measured. The transverse diameter of induration should be recorded in
millimeters. 2. Interpretation of PPD skin tests a. General The
interpretation of a PPD reaction should be influenced by the purpose for
which the test was given (e.g., epidemiologic versus diagnostic purposes), by
the prevalence of TB infection in the population being tested, and by the
consequences of false classification. Errors in classification can be
minimized by establishing an appropriate definition of a positive reaction
(Table S2-1"). The positive-predictive value of PPD tests (i.e, the
probability that a person with a positive PPD test is actually infected with
M. tuberculosis) is dependent on the prevalence of TB infection in the
population being tested and the specificity of the test (69,70). In
populations with a low prevalence of TB infection, the probability that a
positive PPD test represents true infection with M. tuberculosis is very low
if the cut-point is set too low (i.e., the test is not adequately specific). In
populations with a high prevalence of TB infection, the probability that a
positive PPD test using the same cut-point represents true infection with M.
tuberculosis is much higher. To ensure that few persons infected with
tubercle bacilli will be misclassified as having negative reactions and few
persons not infected with tubercle bacilli will be misclassified as having
positive reactions, different cut-points are used to separate positive
reactions from negative reactions for different populations, depending on the
risk for TB infection in that population. A lower cut-point (i.e., 5 mm) is
used for persons in the highest risk groups, which include HIV-infected
persons, recent close contacts of persons with TB (e.g., in the household or
in an unprotected occupational exposure similar in intensity and duration to
household contact), and persons who have abnormal chest radiographs with
fibrotic changes consistent with inactive TB. A higher cut-point (i.e., 10
mm) is used for persons who are not in the highest risk group but who have
other risk factors (e.g., injecting-drug users known to be HIV seronegative;
persons with certain medical conditions that increase the risk for
progression from latent TB infection to active TB [Table S2-1]); medically
under-served, low-income populations; persons born in foreign countries that
have a high prevalence of TB; and residents of correctional institutions and
nursing homes). An even higher cut-point (i.e., 15 mm) is used for all other
persons who have none of the above risk factors. Recent PPD converters are
considered members of a high-risk group. A greater than or equal to 10 mm
increase in the size of the induration within a 2-year period is classified
as a conversion from a negative to a positive test result for persons less
than 35 years of age. An increase of induration of greater than or equal to
15 mm within a 2-year period is classified as a conversion for persons
greater than or equal to 35 years of age (5). b. HCWs In general, HCWs should
have their skin-test results interpreted according to the recommendations in
this supplement and in sections 1, 2, 3, and 5 of Table S2-1. However, the
prevalence of TB in the facility should be considered when choosing the
appropriate cut-point for defining a positive PPD reaction. In facilities
where there is essentially no risk for exposure to TB patients (i.e., minimal-
or very low-risk facilities [Section II.B]), an induration greater than or
equal to 15 mm may be an appropriate cut-point for HCWs who have no other
risk factors. In other facilities where TB patients receive care, the
appropriate cut-point for HCWs who have no other risk factors may be greater
than or equal to 10 mm. A recent PPD test conversion in an HCW should be
defined generally as an increase of greater than or equal to 10 mm in the
size of induration within a 2-year period. For HCWs in facilities where
exposure to TB is very unlikely (e.g., minimal-risk facilities), an increase
of greater than or equal to 15 mm within a 2-year period may be more
appropriate for defining a recent conversion because of the lower
positive-predictive value of the test in such groups. 3. Anergy testing
HIV-infected persons may have suppressed reactions to PPD skin tests because
of anergy, particularly if their CD4+ T-lymphocyte counts decline (71). Persons
with anergy will have a negative PPD test regardless of infection with M.
tuberculosis. HIV-infected testing (72). Two companion antigens (e.g.,
Candida antigen and tetanus toxoid) should be administered in addition to
PPD. Persons with greater than or equal to 3 mm of induration to any of the
skin tests (including tuberculin) are considered not anergic. Reactions of
greater than or equal to 5 mm to PPD are considered to be evidence of TB
infection in HIV-infected persons regardless of the reactions to the
companion antigens. If there is no reaction (i.e., less than 3 mm induration)
to any of the antigens, the person being tested is considered anergic. Determination
of whether such persons are likely to be infected with M. tuberculosis must
be based on other epidemiologic factors (e.g., the proportion of other
persons with the same level of exposure who have positive PPD test results
and the intensity or duration of exposure to infectious TB patients that the
anergic person experienced). 4. Pregnancy and PPD skin testing
Although thousands (perhaps millions) of pregnant women have been PPD skin
tested since the test was devised, thus far no documented episodes of fetal
harm have resulted from use of the tuberculin test (73). Pregnancy should not
exclude a female HCW from being skin tested as part of a contact investigation
or as part of a regular skin-testing program. TABLE S2-1. Summary of interpretation of purified protein derivation (PPD-tubercilin skin-test results ----------------------------------------------------------------------------- 1.
An induration of greater than or equals to 5 mm is classified as positive in: * persons who have human immunodeficiency
virus (HIV) infection or risk factors for HIV infection but unknown HIV
status; * persons who have had recent close contact* with persons who have
active tuberculosis (TB); *
Recent close contact inplies either househould or social contact or
unprotected occupational exposure similar in intensity and duration to
househould contact. * persons who have fibrotic chest radiographs
(consistent with healed TB). 2.
An induration of greater than or equals to 10 mm is classified as positive in
all persons who do not meet any of the criteria above but who have other risk
factors for TB, including: High-risk groups-- * injection-drug users
known to be HIV seronegative; * persons who have other medical conditions
that reportedly increase the risk for progressing from latent TB infection to
active TB (e.g., silicosis; gastrectomy or jejuno-ioeal bypass; being greater
than or equal to 10% below ideal body weight; chronic renal failure with
renal dialysis; diabetes mellitus; high-dose corticosteroid or other
immunosuppressive therapy; some hematologic disorders, including malignancies
such as leukemias and lymphomas; and other malignancies); * children less
than or equal to 4 years of age. High-prevalence groups-- * persons born in
countries in Asia, Africa, the Caribbean, and Latin America that have high
prevalence of TB; * persons from medically underserved, low-income
populations; * residents of long-term-care facilities (e.g., correctional
institutions and nursing homes); * persons from high-risk populations in
their communities, as determined by local public health authorities. 3.
An induration of greater than or equal to 15 mm is classified as positive in
persons who do not meet any of the above criteria. 4.
Recent converters are defined on the basis of both size of induration and age
of the person being tested: * Greater than or equal to 10 mm increase
within a 2-year period is classified as a recent conversion for persons less
than or equal to 35 years of age; * Greater than or equal to 15 mm increase
within a 2-year period is classified as a recent conversion for persons
greater than or equal to 35 years of age. 5.
PPD skin-test results in health-care workers (HCWs) * In general, the recommendations in sections
1, 2, and 3 of this table should be followed when interpreting skin-test
results in HCWs. * However, the prevalence of TB in the facility should be
considered when choosing the appropriate cut-point for defining a positive
PPD reaction. In facilities where there is essentially no risk for exposure
to Mycobacterium tuberculosis (i.e., minimal- or very low-risk facilities
[Section II.B]), an induration greater than or equal 15 mm may be a suitable
cut-point for HCWs who have no other risk factors. In facilities where TB
patients receive care, the cut-pint for HCWs with no other risk factors may
be greater than or equal 10 mm. * A recent conversion in an HCW should be
defined generally as a greater than or equal to 10 mm increase in size of
induration within a 2-year period. For HCWs who work in facilities where
exposure to TB is very unlikely (e.g., minimal-risk facilities), an increase
of greater than or equal to 15 mm within a 2-year period may be more appropriate
for defining a recent conversion because of the lower positive-predictive
value of the test in such groups. ____________________________________________________________________________ 5. BCG vaccination and PPD skin testing BCG vaccination may produce a PPD
reaction that cannot be distinguished reliably from a reaction caused by
infection with M. tuberculosis. For a person who was vaccinated with BCG, the
probability that a PPD test reaction results from infection with M. tuberculosis
increases a) as the size of the reaction increases, b) when the person is a
contact of a person with TB, c) when the person's country of origin has a
high prevalence of TB, and d) as the length of time between vaccination and
PPD testing increases. For example, a PPD test reaction of greater than or
equal to 10 mm probably can be attributed to M. tuberculosis infection in an
adult who was vaccinated with BCG as a child and who is from a country with a
high prevalence of TB (74,75). 6. The booster phenomenon The ability
of persons who have TB infection to react to PPD may gradually wane. For
example, if tested with PPD, adults who were infected during their childhood
may have a negative reaction. However, the PPD could boost the
hypersensitivity, and the size of the reaction could be larger on a
subsequent test. This boosted reaction may be misinterpreted as a PPD test
conversion from a newly acquired infection. Misinterpretation of a boosted
reaction as a new infection could result in unnecessary investigations of
laboratory and patient records in an attempt to identify the source case and
in unnecessary prescription of preventive therapy for HCWs. Although boosting
can occur among persons in any age group, the likelihood of the reaction
increases with the age of the person being tested (6,76). When PPD testing of
adults is to be repeated periodically (as in HCW skin-testing programs),
two-step testing can be used to reduce the likelihood that a boosted reaction
is misinterpreted as a new infection. Two-step testing should be performed on
all newly employed HCWs who have an initial negative PPD test result at the
time of employment and have not had a documented negative PPD test result
during the 12 months preceding the initial test. A second test should be
performed 1-3 weeks after the first test. If the second test result is
positive, this is most likely a boosted reaction, and the HCW should be
classified as previously infected. If the second test result remains
negative, the HCW is classified as uninfected, and a positive reaction to a
subsequent test is likely to represent a new infection with M. tuberculosis. B.
Chest Radiography Patients who have positive skin-test results or
symptoms suggestive of TB should be evaluated with a chest radiograph regardless
of PPD test results. Radiographic abnormalities that strongly suggest active
TB include upper-lobe infiltration, particularly if cavitation is seen (77),
and patchy or nodular infiltrates in the apical or subapical posterior upper
lobes or the superior segment of the lower lobe. If abnormalities are noted,
or if the patient has symptoms suggestive of extrapulmonary TB, additional
diagnostic tests should be conducted. The radiographic presentation of
pulmonary TB in HIV-infected patients may be unusual (78). Typical apical
cavitary disease is less common among such patients. They may have
infiltrates in any lung zone, a finding that is often associated with
mediastinal and/or hilar adenopathy, or they may have a normal chest
radiograph, although this latter finding occurs rarely. C. Bacteriology
Smear and culture examination of at least three sputum specimens collected on
different days is the main diagnostic procedure for pulmonary TB (6). Sputum
smears that fail to demonstrate AFB do not exclude the diagnosis of TB. In
the United States, approximately 60% of patients with positive sputum
cultures have positive AFB sputum smears. HIV-infected patients who have
pulmonary TB may be less likely than immunocompetent patients to have AFB
present on sputum smears, which is consistent with the lower frequency of
cavitary pulmonary disease observed among HIV-infected persons (39,41). Specimens
for smear and culture should contain an adequate amount of expectorated
sputum but not much saliva. If a diagnosis of TB cannot be established from
sputum, a bronchoscopy may be necessary (36,37). In young children who cannot
produce an adequate amount of sputum, gastric aspirates may provide an
adequate specimen for diagnosis. A culture of sputum or other clinical specimen
that contains M. tuberculosis provides a definitive diagnosis of TB. Conventional
laboratory methods may require 4-8 weeks for species identification; however,
the use of radiometric culture techniques and nucleic acid probes facilitates
more rapid detection and identification of mycobacteria (79,80). Mixed
mycobacterial infection, either simultaneous or sequential, can obscure the
identification of M. tuberculosis during the clinical evaluation and the
laboratory analysis (42). The use of nucleic acid probes for both M. avium
complex and M. tuberculosis may be useful for identifying mixed mycobacterial
infections in clinical specimens. II. Preventive Therapy for Latent TB Infection and Treatment of Active
TB A. Preventive Therapy for Latent TB Infection Determining whether a person with
a positive PPD test reaction or conversion is a candidate for preventive
therapy must be based on a) the likelihood that the reaction represents true
infection with M. tuberculosis (as determined by the cut-points), b) the
estimated risk for progression from latent infection to active TB, and c) the
risk for hepatitis associated with taking isoniazid (INH) preventive therapy
(as determined by age and other factors). HCWs with positive PPD test results
should be evaluated for preventive therapy regardless of their ages if they
a) are recent converters, b) are close contacts of persons who have active
TB, c) have a medical condition that increases the risk for TB, d) have HIV
infection, or e) use injecting drugs (5). HCWs with positive PPD test results
who do not have these risk factors should be evaluated for preventive therapy
if they are less than 35 years of age. Preventive therapy should be
considered for anergic persons who are known contacts of infectious TB
patients and for persons from populations in which the prevalence of TB
infection is very high (e.g., a prevalence of greater than 10%). Because the
risk for INH-associated hepatitis may be increased during the peripartum period,
the decision to use preventive therapy during pregnancy should be made on an
individual basis and should depend on the patient's estimated risk for
progression to active disease. In general, preventive therapy can be delayed
until after delivery. However, for pregnant women who were probably infected
recently or who have high-risk medical conditions, especially HIV infection,
INH preventive therapy should begin when the infection is documented (81-84).
No evidence suggests that INH poses a carcinogenic risk to humans (85-87). The
usual preventive therapy regimen is oral INH 300 mg daily for adults and 10
mg/kg/day for children (88). The recommended duration of therapy is 12 months
for persons with HIV infection and 9 months for children. Other persons should
receive INH therapy for 6-12 months. For persons who have silicosis or a
chest radiograph demonstrating inactive fibrotic lesions and who have no
evidence of active TB, acceptable regimens include a) 4 months of INH plus
rifampin or b) 12 months of INH, providing that infection with INH-resistant
organisms is unlikely (33). For persons likely to be infected with MDR-TB,
alternative multidrug preventive therapy regimens should be considered (89). All
persons placed on preventive therapy should be educated regarding the
possible adverse reactions associated with INH use, and they should be
questioned carefully at monthly intervals by qualified personnel for signs or
symptoms consistent with liver damage or other adverse effects
(81-84,88,90,91). Because INH-associated hepatitis occurs more frequently
among persons greater than 35 years of age, a transaminase measurement should
be obtained from persons in this age group before initiation of INH therapy
and then obtained monthly until treatment has been completed. Other factors
associated with an increased risk for hepatitis include daily alcohol use,
chronic liver disease, and injecting-drug use. In addition, postpubertal
black and Hispanic women may be at greater risk for hepatitis or drug
interactions (92). More careful clinical monitoring of persons with these
risk factors and possibly more frequent laboratory monitoring should be
considered. If any of these tests exceeds three to five times the upper limit
of normal, discontinuation of INH should be strongly considered. Liver
function tests are not a substitute for monthly clinical evaluations or for
the prompt assessment of signs or symptoms of adverse reactions that could
occur between the regularly scheduled evaluations (33). Persons who have
latent TB infection should be advised that they can be reinfected with
another strain of M. tuberculosis (93). B. Treatment of Patients Who Have
Active TB Drug-susceptibility testing should be performed on all initial
isolates from patients with TB. However, test results may not be available
for several weeks, making selection of an initial regimen difficult,
especially in areas where drug-resistant TB has been documented. Current
recommendations for therapy and dosage schedules for the treatment of
drug-susceptible TB should be followed (Table S2-2) (43). Streptomycin is
contraindicated in the treatment of pregnant women because of the risk for
ototoxicity to the fetus. In geographic areas or facilities in which
drug-resistant TB is highly prevalent, the initial treatment regimen used
while results of drug-susceptibility tests are pending may need to be
expanded. This decision should be based on analysis of surveillance data. When
results from drug-susceptibility tests become available, the regimen should
be adjusted appropriately (94-97). If drug resistance is present, clinicians
unfamiliar with the management of patients with drug-resistant TB should seek
expert consultation. For any regimen to be effective, adherence to the
regimen must be ensured. The most effective method of ensuring adherence is
the use of DOT after the patient has been discharged from the hospital
(43,91). This practice should be coordinated with the public health
department. (For Table S2-2, see printed copy) (For Table S2-3, see printed copy) Supplement 3: Engineering Controls I. Introduction This supplement provides information
regarding the use of ventilation (Section II) and UVGI (Section III) for
preventing the transmission of M. tuberculosis in health-care facilities. The
information provided is primarily conceptual and is intended to educate staff
in the health-care facility concerning engineering controls and how these
controls can be used as part of the TB infection-control program. This
supplement should not be used in place of consultation with experts, who can
assume responsibility for advising on ventilation system design and
selection, installation, and maintenance of equipment. The recommendations
for engineering controls include a) local exhaust ventilation (i.e., source
control), b) general ventilation, and c) air cleaning. General ventilation
considerations include a) dilution and removal of contaminants, b) airflow
patterns within rooms, c) airflow direction in facilities, d) negative
pressure in rooms, and e) TB isolation rooms. Air cleaning or disinfection
can be accomplished by filtration of air (e.g., through HEPA filters) or by
UVGI. II. Ventilation Ventilation systems for health-care
facilities should be designed, and modified when necessary, by ventilation
engineers in collaboration with infection-control and occupational health
staff. Recommendations for designing and operating ventilation systems have
been published by ASHRAE (47), AIA (48), and the American Conference of
Governmental Industrial Hygienists, Inc. (98). As part of the TB
infection-control plan, health-care facility personnel should determine the
number of TB isolation rooms, treatment rooms, and local exhaust devices
(i.e., for cough-inducing or aerosol-generating procedures) that the facility
needs. The locations of these rooms and devices will depend on where in the
facility the ventilation conditions recommended in this document can be
achieved. Grouping isolation rooms together in one area of the facility may
facilitate the care of TB patients and the installation and maintenance of
optimal engineering controls (particularly ventilation). Periodic evaluations
of the ventilation system should review the number of TB isolation rooms,
treatment rooms, and local exhaust devices needed and the regular maintenance
and monitoring of the local and general exhaust systems (including HEPA
filtration systems if they are used). The various types and conditions of
ventilation systems in health-care facilities and the individual needs of
these facilities preclude the ability to provide specific instructions
regarding the implementation of these recommendations. Engineering control
methods must be tailored to each facility on the basis of need and the
feasibility of using the ventilation and air-cleaning concepts discussed in
this supplement. A. Local Exhaust Ventilation Purpose: To capture
airborne contaminants at or near their source (i.e., the source control
method) and remove these contaminants without exposing persons in the area to
infectious agents (98). Source control techniques can prevent or reduce the
spread of infectious droplet nuclei into the general air circulation by
entrapping infectious droplet nuclei as they are being emitted by the patient
(i.e., the source). These techniques are especially important when performing
procedures likely to generate aerosols containing infectious particles and
when infectious TB patients are coughing or sneezing. Local exhaust
ventilation is a preferred source control technique, and it is often the most
efficient way to contain airborne such as leukemias and lymphomas; and other
source before they can disperse. Therefore, the technique should be used, if
feasible, wherever aerosol-generating procedures are performed. Two basic
types of local exhaust devices use hoods: a) the enclosing type, in which the
hood either partially or fully encloses the infectious source; and b) the
exterior type, in which the infectious source is near but outside the hood. Fully
enclosed hoods, booths, or tents are always preferable to exterior types
because of their superior ability to prevent contaminants from escaping into
the HCW's breathing zone. Descriptions of both enclosing and exterior devices
have been published previously (98). 1. Enclosing devices The
enclosing type of local exhaust ventilation device includes laboratory hoods
used for processing specimens that could contain viable infectious organisms,
booths used for sputum induction or administration of aerosolized medications
(e.g., aerosolized pentamidine) (Figure S3-1), and tents or hoods made of
vinyl or other materials used to enclose and isolate a patient. These devices
are available in various configurations. The most simple of these latter
devices is a tent that is placed over the patient; the tent has an exhaust
connection to the room discharge exhaust system. The most complex device is
an enclosure that has a sophisticated self-contained airflow and
recirculation system. Both tents and booths should have sufficient airflow to
remove at least 99% of airborne particles during the interval between the
departure of one patient and the arrival of the next (99). The time required
for removing a given percentage of airborne particles from an enclosed space
depends on several factors. These factors include the number of ACH, which is
determined by the number of cubic feet of air in the room or booth and the
rate at which air is entering the room or booth at the intake source; the
location of the ventilation inlet and outlet; and the physical configuration
of the room or booth (Table S3-1). TABLE
S3-1. Air changes per hour (ACH) and time in minutes required for removal
efficiencies of 90%, 99%, and 99.9% of airborne contaminants* Minutes required for a removal efficiency of:
ACH
90% 99% 99.9% 1 138 276 414 2 69 138 207 3 46 92 138 4 35
69 104 5 28 55 83 6 23 46 69 7 20 39 59 8 17 35 52 9 15 31 46 10 14 28 41 11
13 25 38 12 12 23 35 13 11 21 32 14 10 20 30 15 9 18 28 16 9 17 26 17 8 16 24
18 8 15 23 19 7 15 22 20 7 14 21 25 6 11 17 30 5 9 14 35 4 8 12 40 3 7 10 45
3 6 9 50 3 6 8 ----------------------------------------------------------------------------- *
This table has been adapted from the formula for the rate of purging airborne
contaminats (99). Values have been derived from the formula t(1) = [In (C(2)
divide C(1) + (Q divide V)] x 60, with T(1) = 0 and C(2) divide C(1) -
(removal efficiency divide 100), and where: t(1) = initial timepoint C(1) = initial
concentration of contaminant C(2) = final concentration of contaminants Q =
air flow rate (cubic feet per hour) V = room volume (cubic feet) Q divide V =
ACH The times given assume perfect mixing of the air within the space (i.e.,
mixing factor = 1). However, perfect mixing usually does not occur, and the
mixing factor could be as high as 10 if air distribution is very poor (98). The
required time is derived by multiplying the appropriate time from the tale by
the mixing factor that has been determined for the booth or room. The factor
and required time should be included in the operating instructions provided
by the manufacturer of the booth or enclosure, and these instructions should
be followed. 2. Exterior devices The exterior type of local exhaust
ventilation device is usually a hood very near, but not enclosing, the
infectious patient. The airflow produced by these devices should be
sufficient to prevent cross-currents of air near the patient's face from
causing escape of droplet nuclei. Whenever possible, the patient should face
directly into the hood opening so that any coughing or sneezing is directed
into the hood, where the droplet nuclei are captured. The device should maintain
an air velocity of greater than or equal to 200 feet per minute at the
patient's breathing zone to ensure capture of droplet nuclei. 3. Discharge
exhaust from booths, tents, and hoods Air from booths, tents, and hoods
may be discharged into the room in which the device is located or it may be
exhausted to the outside. If the air is discharged into the room, a HEPA
filter should be incorporated at the discharge duct or vent of the device. The
exhaust fan should be located on the discharge side of the HEPA filter to
ensure that the air pressure in the filter housing and booth is negative with
respect to adjacent areas. Uncontaminated air from the room will flow into
the booth through all openings, thus preventing infectious droplet nuclei in
the booth from escaping into the room. Most commercially available booths,
tents, and hoods are fitted with HEPA filters, in which case additional HEPA
filtration is not needed. If the device does not incorporate a HEPA filter,
the air from the device should be exhausted to the outside in accordance with
recommendations for isolation room exhaust (Suppl. 3, Section II.B.5). (See
Supplement 3, Section II.C, for information regarding recirculation of
exhaust air.) B. General Ventilation General ventilation can be used
for several purposes, including diluting and removing contaminated air,
controlling airflow patterns within rooms, and controlling the direction of
airflow throughout a facility. Information on these topics is contained in
the following sections. 1. Dilution and removal Purpose: To reduce the concentration of
contaminants in the air. General ventilation maintains air quality by
two processes: dilution and removal of airborne contaminants. Uncontaminated
supply (i.e., incoming) air mixes with the contaminated room air (i.e.,
dilution), which is subsequently removed from the room by the exhaust system
(i.e., removal). These processes reduce the concentration of droplet nuclei
in the room air. a. Types of general ventilation systems Two types of general ventilation systems can
be used for dilution and removal of contaminated air: the single-pass system
and the recirculating system. In a single-pass system, the supply air is
either outside air that has been appropriately heated and cooled or air from
a central system that supplies a number of areas. After air passes through
the room (or area), 100% of that air is exhausted to the outside. The
single-pass system is the preferred choice in areas where infectious airborne
droplet nuclei are known to be present (e.g., TB isolation rooms or treatment
rooms) because it prevents contaminated air from being recirculated to other
areas of the facility. In a recirculating system, a small portion of the
exhaust air is discharged to the outside and is replaced with fresh outside
air, which mixes with the portion of exhaust air that was not discharged to
the outside. The resulting mixture, which can contain a large proportion of
contaminated air, is then recirculated to the areas serviced by the system. This
air mixture could be recirculated into the general ventilation, in which case
contaminants may be carried from contaminated areas to uncontaminated areas. Alternatively,
the air mixture could also be recirculated within a specific room or area, in
which case other areas of the facility will not be affected (Suppl. 3,
Section II.C.3). b. Ventilation rates Recommended general ventilation rates
for health-care facilities are usually expressed in number of ACH. This
number is the ratio of the volume of air entering the room per hour to the
room volume and is equal to the exhaust airflow (Q [cubic feet per minute])
divided by the room volume (V [cubic feet]) multiplied by 60 (i.e., ACH = Q /
V x 60). The feasibility of achieving specific ventilation rates depends on
the construction and operational requirements of the ventilation system
(e.g., the energy requirements to move and to heat or cool the air). The
feasibility of achieving specific ventilation rates may also be different for
retrofitted facilities and newly constructed facilities. The expense and
effort of achieving specific higher ventilation rates for new construction
may be reasonable, whereas retrofitting an existing facility to achieve
similar ventilation rates may be more difficult. However, achieving higher
ventilation rates by using auxiliary methods (e.g., room-air recirculation)
in addition to exhaust ventilation may be feasible in existing facilities
(Suppl. 3, Section II.C). 2. Airflow patterns within rooms (air mixing)
Purpose: To provide optimum airflow patterns and prevent both stagnation and
short-circuiting of air. General ventilation systems should be designed to
provide optimal patterns of airflow within rooms and prevent air stagnation
or short-circuiting of air from the supply to the exhaust (i.e., passage of
air directly from the air supply to the air exhaust). To provide optimal
airflow patterns, the air supply and exhaust should be located such that
clean air first flows to parts of the room where HCWs are likely to work, and
then flows across the infectious source and into the exhaust. In this way,
the HCW is not positioned between the infectious source and the exhaust
location. Although this configuration may not always be possible, it should
be used whenever feasible. One way to achieve this airflow pattern is to
supply air at the side of the room opposite the patient and exhaust it from
the side where the patient is located. Another method, which is most
effective when the supply air is cooler than the room air, is to supply air
near the ceiling and exhaust it near the floor (Figure S3-2). Airflow
patterns are affected by large air temperature differentials, the precise
location of the supply and exhausts, the location of furniture, the movement
of HCWs and patients, and the physical configuration of the space. Smoke
tubes can be used to visualize airflow patterns in a manner similar to that
described for estimating room air mixing. Adequate air mixing, which requires
that an adequate number of ACH be provided to a room (Suppl. 3, Section
II.B.1), must be ensured to prevent air stagnation within the room. However,
the air will not usually be changed the calculated number of times per hour
because the airflow patterns in the room may not permit complete mixing of
the supply and room air in all parts of the room. This results in an
"effective" airflow rate in which the supplied airflow may be less
than required for proper ventilation. To account for this variation, a mixing
factor (which ranges from 1 for perfect mixing to 10 for poor mixing) is
applied as a multiplier to determine the actual supply airflow (i.e., the
recommended ACH multiplied by the mixing factor equals the actual required
ACH) (51,98). The room air supply and exhaust system should be designed to
achieve the lowest mixing factor possible. The mixing factor is determined
most accurately by experimentally testing each space configuration, but this
procedure is complex and time-consuming. A reasonably good qualitative
measure of mixing can be estimated by an experienced ventilation engineer who
releases smoke from smoke tubes at a number of locations in the room and
observes the movement of the smoke. Smoke movement in all areas of the room
indicates good mixing. Stagnation of air in some areas of the room indicates
poor mixing, and movement of the supply and exhaust openings or redirection
of the supply air is necessary. (For Figure S3-2, see printed copy) 3. Airflow direction in the facility Purpose: To contain contaminated
air in localized areas in a facility and prevent its spread to uncontaminated
areas. a. Directional airflow The general ventilation system should be
designed and balanced so that air flows from less contaminated (i.e., more
clean) to more contaminated (less clean) areas (47,48). For example, air
should flow from corridors (cleaner areas) into TB isolation rooms (less
clean areas) to prevent spread of contaminants to other areas. In some
special treatment rooms in which operative and invasive procedures are
performed, the direction of airflow is from the room to the hallway to provide
cleaner air during these procedures. Cough-inducing or aerosol-generating
procedures (e.g., bronchoscopy and irrigation of tuberculous abscesses)
should not be performed in rooms with this type of airflow on patients who
may have infectious TB. b. Negative pressure for achieving
directional airflow The direction of airflow is controlled by
creating a lower (negative) pressure in the area into which the flow of air
is desired. For air to flow from one area to another, the air pressure in the
two areas must be different. Air will flow from a higher pressure area to a
lower pressure area. The lower pressure area is described as being at
negative* pressure relative to the higher pressure area. Negative pressure is
attained by exhausting air from an area at a higher rate than air is being
supplied. The level of negative pressure necessary to achieve the desired
airflow will depend on the physical configuration of the ventilation system
and area, including the airflow path and flow openings, and should be determined
on an individual basis by an experienced ventilation engineer. __________ *
Negative is defined relative to the air pressure in the area from which air
is to flow. 4. Achieving negative pressure in a room Purpose: To control the direction
of airflow between the room and adjacent areas, thereby preventing
contaminated air from escaping from the room into other areas of the
facility. a. Pressure differential The minimum pressure difference necessary
to achieve and maintain negative pressure that will result in airflow into
the room is very small (0.001 inch of water). Higher pressures ( greater than
or equal to 0.001 inch of water) are satisfactory; however, these higher
pressures may be difficult to achieve. The actual level of negative pressure
achieved will depend on the difference in the ventilation exhaust and supply
flows and the physical configuration of the room, including the airflow path
and flow openings. If the room is well sealed, negative pressures greater
than the minimum of 0.001 inch of water may be readily achieved. However, if
rooms are not well sealed, as may be the case in many facilities (especially
older facilities), achieving higher negative pressures may require
exhaust/supply flow differentials beyond the capability of the ventilation
system. To establish negative pressure in a room that has a normally
functioning ventilation system, the room supply and exhaust airflows are
first balanced to achieve an exhaust flow of either 10% or 50 cubic feet per
minute (cfm) greater than the supply (whichever is the greater). In most
situations, this specification should achieve a negative pressure of at least
0.001 inch of water. If the minimum 0.001 inch of water is not achieved and
cannot be achieved by increasing the flow differential (within the limits of
the ventilation system), the room should be inspected for leakage (e.g.,
through doors, windows, plumbing, and equipment wall penetrations), and
corrective action should be taken to seal the leaks. Negative pressure in a
room can be altered by changing the ventilation system operation or by the
opening and closing of the room's doors, corridor doors, or windows. When an
operating configuration has been established, it is essential that all doors
and windows remain properly closed in the isolation room and other areas
(e.g., doors in corridors that affect air pressure) except when persons need
to enter or leave the room or area. b. Alternate methods for achieving negative
pressure Although an anteroom is not a substitute for
negative pressure in a room, it may be used to reduce escape of droplet
nuclei during opening and closing of the isolation room door. Some anterooms
have their own air supply duct, but others do not. The TB isolation room
should have negative pressure relative to the anteroom, but the air pressure
in the anteroom relative to the corridor may vary depending on the building
design. This should be determined, in accordance with applicable regulations,
by a qualified ventilation engineer. If the existing ventilation system is
incapable of achieving the desired negative pressure because the room lacks a
separate ventilation system or the room's system cannot provide the proper
airflow, steps should be taken to provide a means to discharge air from the
room. The amount of air to be exhausted will be the same as discussed
previously (Suppl. 3, Section II.B.4.a). Fixed room-air recirculation systems
(i.e., systems that recirculate the air in an entire room) may be designed to
achieve negative pressure by discharging air outside the room (Suppl. 3,
Section II.C.3). Some portable room-air recirculation units (Suppl. 3,
Section II.C.3.b.) are designed to discharge air to the outside to achieve
negative pressure. Air cleaners that can accomplish this must be designed
specifically for this purpose. A small centrifugal blower (i.e., exhaust fan)
can be used to exhaust air to the outside through a window or outside wall. This
approach may be used as an interim measure to achieve negative pressure, but
it provides no fresh air and suboptimal dilution. Another approach to
achieving the required pressure difference is to pressurize the corridor. Using
this method, the corridor's general ventilation system is balanced to create
a higher air pressure in the corridor than in the isolation room; the type of
balancing necessary depends on the configuration of the ventilation system. Ideally,
the corridor air supply rate should be increased while the corridor exhaust
rate is not increased. If this is not possible, the exhaust rate should be
decreased by resetting appropriate exhaust dampers. Caution should be
exercised, however, to ensure that the exhaust rate is not reduced below
acceptable levels. This approach requires that all settings used to achieve
the pressure balance, including doors, be maintained. This method may not be
desirable if the corridor being pressurized has rooms in which negative
pressure is not desired. In many situations, this system is difficult to
achieve, and it should be considered only after careful review by ventilation
personnel. c. Monitoring negative pressure The negative pressure in a room
can be monitored by visually observing the direction of airflow (e.g., using
smoke tubes) or by measuring the differential pressure between the room and
its surrounding area. Smoke from a smoke tube can be used to observe airflow
between areas or airflow patterns within an area. To check the negative
pressure in a room by using a smoke tube, hold the smoke tube near the bottom
of the door and approximately 2 inches in front of the door, or at the face
of a grille or other opening if the door has such a feature, and generate a
small amount of smoke by gently squeezing the bulb (Figure S3-3). The smoke
tube should be held parallel to the door, and the smoke should be issued from
the tube slowly to ensure the velocity of the smoke from the tube does not
overpower the air velocity. The smoke will travel in the direction of
airflow. If the room is at negative pressure, the smoke will travel under the
door and into the room (e.g., from higher to lower pressure). If the room is
not at negative pressure, the smoke will be blown outward or will stay
stationary. This test must be performed while the door is closed. If room air
cleaners are being used in the room, they should be running. The smoke is
irritating if inhaled, and care should be taken not to inhale it directly
from the smoke tube. However, the quantity of smoke issued from the tube is
minimal and is not detectable at short distances from the tube. Differential
pressure-sensing devices also can be used to monitor negative pressure; they
can provide either periodic (noncontinuous) pressure measurements or
continuous pressure monitoring. The continuous monitoring component may
simply be a visible and/or audible warning signal that air pressure is low. In
addition, it may also provide a pressure readout signal, which can be
recorded for later verification or used to automatically adjust the
facility's ventilation control system. Pressure-measuring devices should
sense the room pressure just inside the airflow path into the room (e.g., at
the bottom of the door). Unusual airflow patterns within the room can cause
pressure variations; for example, the air can be at negative pressure at the
middle of a door and at positive pressure at the bottom of the same door
(Figure S-34). If the pressure-sensing ports of the device cannot be located
directly across the airflow path, it will be necessary to validate that the
negative pressure at the sensing point is and remains the same as the
negative pressure across the flow path. (For Figure S3-3, see printed copy) Pressure-sensing devices should incorporate
an audible warning with a time delay to indicate that a door is open. When
the door to the room is opened, the negative pressure will decrease. The
time-delayed signal should allow sufficient time for persons to enter or
leave the room without activating the audible warning. A potential problem
with using pressure-sensing devices is that the pressure differentials used
to achieve the low negative pressure necessitate the use of very sensitive
mechanical devices, electronic devices, or pressure gauges to ensure accurate
measurements. Use of devices that cannot measure these low pressures (i.e.,
pressures as low as 0.001 inch of water) will require setting higher negative
pressures that may be difficult and, in some instances, impractical to
achieve (Suppl. 3, Section II.B.4). Periodic checks are required to ensure
that the desired negative pressure is present and that the continuous
monitoring devices, if used, are operating properly. If smoke tubes or other
visual checks are used, TB isolation rooms and treatment rooms should be
checked frequently for negative pressure. Rooms undergoing changes to the
ventilation system should be checked daily. TB isolation rooms should be
checked daily for negative pressure while being used for TB isolation. If
these rooms are not being used for patients who have suspected or confirmed
TB but potentially could be used for such patients, the negative pressure in
the rooms should be checked monthly. If pressure-sensing devices are used,
negative pressure should be verified at least once a month by using smoke
tubes or taking pressure measurements. (For Figure S3-4, see printed copy) C. HEPA filtration Purpose: To remove contaminants
from the air. HEPA filtration can be used as a method of air cleaning that
supplements other recommended ventilation measures. For the purposes of these
guidelines, HEPA filters are defined as air-cleaning devices that have a
demonstrated and documented minimum removal efficiency of 99.97% of particles
greater than or equal to 0.3 um in diameter. HEPA filters have been shown to
be effective in reducing the concentration of Aspergillus spores (which range
in size from 1.5 um to 6 um) to below measurable levels (100-102). The
ability of HEPA filters to remove tubercle bacilli from the air has not been
studied, but M. tuberculosis droplet nuclei probably range from 1 um to 5 um
in diameter (i.e., approximately the same size as Aspergillus spores). Therefore,
HEPA filters can be expected to remove infectious droplet nuclei from
contaminated air. HEPA filters can be used to clean air before it is
exhausted to the outside, recirculated to other areas of a facility, or
recirculated within a room. If the device is not completely passive (e.g., it
utilizes techniques such as electrostatics) and the failure of the
electrostatic components permits loss of filtration efficiency to less than
99.97%, the device should not be used in systems that recirculate air back
into the general facility ventilation system from TB isolation rooms and
treatment rooms in which procedures are performed on patients who may have
infectious TB (Suppl. 3, Section II.C.2). HEPA filters can be used in a number
of ways to reduce or eliminate infectious droplet nuclei from room air or
exhaust. These methods include placement of HEPA filters a) in exhaust ducts
to remove droplet nuclei from air being discharged to the outside, either
directly or through ventilation equipment; b) in ducts discharging room air
into the general ventilation system; and c) in fixed or portable room-air
cleaners. The effectiveness of portable HEPA room-air cleaning units has not
been evaluated adequately, and there is probably considerable variation in
their effectiveness. HEPA filters can also be used in exhaust ducts or vents
that discharge air from booths or enclosures into the surrounding room
(Suppl. 3, Section II.A.3). In any application, HEPA filters should be
installed carefully and maintained meticulously to ensure adequate function. Manufacturers
of room-air cleaning equipment should provide documentation of the HEPA
filter efficiency and the efficiency of the installed device in lowering
room-air contaminant levels. 1. Use of HEPA filtration when exhausting air
to the outside HEPA filters can be used as an added safety measure to
clean air from isolation rooms and local exhaust devices (i.e., booths,
tents, or hoods used for cough-inducing procedures) before exhausting it directly
to the outside, but such use is unnecessary if the exhaust air cannot
re-enter the ventilation system supply. The use of HEPA filters should be
considered wherever exhaust air could possibly reenter the system. In many
instances, exhaust air is not discharged directly to the outside; rather, the
air is directed through heat-recovery devices (e.g., heat wheels). Heat
wheels are often used to reduce the costs of operating ventilation systems
(103). If such units are used with the system, a HEPA filter should also be
used. As the wheel rotates, energy is transferred into or removed from the
supply inlet air stream. The HEPA filter should be placed upstream from the
heat wheel because of the potential for leakage across the seals separating
the inlet and exhaust chambers and the theoretical possibility that droplet
nuclei could be impacted on the wheel by the exhaust air and subsequently
stripped off into the supply air. 2. Recirculation of HEPA-filtered air to
other areas of a facility Air from TB isolation rooms and treatment rooms
used to treat patients who have confirmed or suspected infectious TB should
be exhausted to the outside in accordance with applicable federal, state, and
local regulations. The air should not be recirculated into the general ventilation.
In some instances, recirculation of air into the general ventilation system
from such rooms is unavoidable (i.e., in existing facilities in which the
ventilation system or facility configuration makes venting the exhaust to the
outside impossible). In such cases, HEPA filters should be installed in the
exhaust duct leading from the room to the general ventilation system to
remove infectious organisms and particulates the size of droplet nuclei from
the air before it is returned to the general ventilation system (Section
II.F; Suppl. 3). Air from TB isolation rooms and treatment rooms in new or
renovated facilities should not be recirculated into the general ventilation
system. 3. Recirculation of HEPA-filtered air within a room Individual
room-air recirculation can be used in areas where there is no general
ventilation system, where an existing system is incapable of providing
adequate airflow, or where an increase in ventilation is desired without
affecting the fresh air supply or negative pressure system already in place. Recirculation
of HEPA-filtered air within a room can be achieved in several ways: a) by
exhausting air from the room into a duct, filtering it through a HEPA filter
installed in the duct, and returning it to the room (Figure S3-5); b) by
filtering air through HEPA recirculation systems mounted on the wall or
ceiling of the room (Figure S3-6); or c) by filtering air through portable
HEPA recirculation systems. In this document, the first two of these
approaches are referred to as fixed room-air recirculation systems, because
the HEPA filter devices are fixed in place and are not easily movable. (For Figure S3-5, see printed copy) (For Figure S3-6, see printed copy) a. Fixed room-air recirculation systems The preferred method of recirculating
HEPA-filtered air within a room is a built-in system, in which air is
exhausted from the room into a duct, filtered through a HEPA filter, and
returned to the room (Figure S3-5). This technique may be used to add air
changes in areas where there is a recommended minimum ACH that is difficult
to meet with general ventilation alone. The air does not have to be
conditioned, other than by the filtration, and this permits higher airflow
rates than the general ventilation system can usually achieve. An alternative
is the use of HEPA filtration units that are mounted on the wall or ceiling
of the room (Figure S3-7). Fixed recirculation systems are preferred over
portable (free-standing) units because they can be installed and maintained
with a greater degree of reliability. b. Portable room-air recirculation units Portable HEPA filtration units may be
considered for recirculating air within rooms in which there is no general
ventilation system, where the system is incapable of providing adequate
airflow, or where increased effectiveness in room airflow is desired. Effectiveness
depends on circulating as much of the air in the room as possible through the
HEPA filter, which may be difficult to achieve and evaluate. The
effectiveness of a particular unit can vary depending on the room's
configuration, the furniture and persons in the room, and placement of the
HEPA filtration unit and the supply and exhaust grilles. Therefore, the
effectiveness of the portable unit may vary considerably in rooms with
different configurations or in the same room if moved from one location to
another in the room. If portable units are used, caution should be exercised
to ensure they can recirculate all or nearly all of the room air through the
HEPA filter. Some commercially available units may not be able to meet this
requirement because of design limitations or insufficient airflow capacity. In
addition, units should be designed and operated to ensure that persons in the
room cannot interfere with or otherwise compromise the functioning of the
unit. Portable HEPA filtration units have not been evaluated adequately to
determine their role in TB infection-control programs. Portable HEPA
filtration units should be designed to achieve the equivalent of greater than
or equal to 12 ACH. They should also be designed to ensure adequate air
mixing in all areas of the hospital rooms in which they are used, and they
should not interfere with the current ventilation system. Some HEPA
filtration units employ UVGI for disinfecting air after HEPA filtration. However,
whether exposing the HEPA-filtered air to UV irradiation further decreases
the concentration of contaminants is not known. c. Evaluation of room-air recirculation
systems and units Detailed and accurate evaluations of room-air
recirculation systems and units require the use of sophisticated test
equipment and lengthy test procedures that are not practical. However, an
estimate of the unit's ability to circulate the air in the room can be made
by visualizing airflow patterns as was described previously for estimating
room air mixing (Suppl. 3, Section II.B.1). If the air movement is good in
all areas of the room, the unit should be effective. 4. Installing,
maintaining, and monitoring HEPA filters Proper installation and testing
and meticulous maintenance are critical if a HEPA filtration system is used
(104), especially if the system used recirculates air to other parts of the
facility. Improper design, installation, or maintenance could allow
infectious particles to circumvent filtration and escape into the general
ventilation system (47). HEPA filters should be installed to prevent leakage
between filter segments and between the filter bed and its frame. A regularly
scheduled maintenance program is required to monitor the HEPA filter for
possible leakage and for filter loading. A quantitative leakage and filter
performance test (e.g., the dioctal phthalate [DOP] penetration test [105])
should be performed at the initial installation and every time the filter is
changed or moved. The test should be repeated every 6 months for filters in
general-use areas and in areas with systems that exhaust air that is likely
to be contaminated with M. tuberculosis (e.g, TB isolation rooms). A
manometer or other pressure-sensing device should be installed in the filter
system to provide an accurate and objective means of determining the need for
filter replacement. Pressure drop characteristics of the filter are supplied
by the manufacturer of the filter. Installation of the filter should allow
for maintenance that will not contaminate the delivery system or the area
served. For general infection-control purposes, special care should be taken
to not jar or drop the filter element during or after removal. The scheduled
maintenance program should include procedures for installation, removal, and
disposal of filter elements. HEPA filter maintenance should be performed only
by adequately trained personnel. Appropriate respiratory protection should be
worn while performing maintenance and testing procedures. In addition, filter
housing and ducts leading to the housing should be labelled clearly with the
words "Contaminated Air" (or a similar warning). When a HEPA filter
is used, one or more lower efficiency disposable prefilters installed
upstream will extend the useful life of the HEPA filter. A disposable filter
can increase the life of a HEPA filter by 25%. If the disposable filter is
followed by a 90% extended surface filter, the life of the HEPA filter can be
extended almost 900% (98). These prefilters should be handled and disposed of
in the same manner as the HEPA filter. D. TB Isolation Rooms and Treatment
Rooms Purpose: To separate patients who are likely to have infectious TB
from other persons, to provide an environment that will allow reduction of
the concentration of droplet nuclei through various engineering methods, and
to prevent the escape of droplet nuclei from such rooms into the corridor and
other areas of the facility using directional airflow. A hierarchy of
ventilation methods used to achieve a reduction in the concentration of
droplet nuclei and to achieve directional airflow using negative pressure has
been developed (Table S3-2). The methods are listed in order from the most
desirable to the least desirable. The method selected will depend on the
configuration of the isolation room and the ventilation system in the
facility; the determination should be made in consultation with a ventilation
engineer. (For Table S3-2, see printed copy) 1. Preventing the escape of droplet nuclei
from the room
Rooms used for TB isolation should be single-patient rooms with negative
pressure relative to the corridor or other areas connected to the room. Doors
between the isolation room and other areas should remain closed except for
entry into or exit from the room. The room's openings (e.g., windows and
electrical and plumbing entries) should be sealed as much as possible. However,
a small gap of 1/8 to 1/2 inch should be at the bottom of the door to provide
a controlled airflow path. Proper use of negative pressure will prevent
contaminated air from escaping the room. 2. Reducing the concentration of
droplet nuclei in the room ASHRAE (47), AIA (48), and the Health
Resources and Services Administration (49) recommend a minimum of 6 ACH for
TB isolation rooms and treatment rooms. This ventilation rate is based on
comfort- and odor-control considerations. The effectiveness of this level of
airflow in reducing the concentration of droplet nuclei in the room, thus
reducing the transmission of airborne pathogens, has not been evaluated
directly or adequately. Ventilation rates greater than 6 ACH are likely to
produce an incrementally greater reduction in the concentration of bacteria
in a room than are lower rates (50-52). However, accurate quantitation of
decreases in risk that would result from specific increases in general
ventilation levels has not been performed and may not be possible. To reduce
the concentration of droplet nuclei, TB isolation rooms and treatment rooms
in existing health-care facilities should have an airflow of greater than or
equal to 6 ACH. Where feasible, this airflow rate should be increased to
greater than or equal to 12 ACH by adjusting or modifying the ventilation
system or by using auxiliary means (e.g., recirculation of air through fixed
HEPA filtration units or portable air cleaners) (Suppl. 3, Section II.C)
(53). New construction or renovation of existing health-care facilities
should be designed so that TB isolation rooms achieve an airflow of greater
than or equal to 12 ACH. 3. Exhaust from TB isolation rooms and treatment
rooms Air from TB isolation rooms and treatment rooms in which patients
with infectious TB may be examined should be exhausted directly to the
outside of the building and away from air-intake vents, persons, and animals
in accordance with federal, state, and local regulations concerning
environmental discharges. (See Suppl. 3, Section II.C, for information
regarding recirculation of exhaust air.) Exhaust ducts should not be located
near areas that may be populated (e.g., near sidewalks or windows that could
be opened). Ventilation system exhaust discharges and inlets should be
designed to prevent reentry of exhausted air. Wind blowing over a building
creates a highly turbulent recirculation zone, which can cause exhausted air
to reenter the building (Figure S3-7). Exhaust flow should be discharged
above this zone (Suppl. 3, Section II.C.1). Design guidelines for proper
placement of exhaust ducts can be found in the 1989 ASHRAE Fundamentals
Handbook (106). If recirculation of air from such rooms into the general
ventilation system is unavoidable, the air should be passed through a HEPA
filter before recirculation (Suppl. 3, Section II.C.2). 4. Alternatives to
TB isolation rooms Isolation can also be achieved by use of negative-pressure
enclosures (e.g, tents or booths) (Suppl. 3, Section II.A.1). These can be
used to provide patient isolation in areas such as emergency rooms and
medical testing and treatment areas and to supplement isolation in designated
isolation rooms. III. UVGI Purpose: To kill or inactivate airborne
tubercle bacilli. Research has demonstrated that UVGI is effective in killing
or inactivating tubercle bacilli under experimental conditions (66,107-110)
and in reducing transmission of other infections in hospitals (111), military
housing (112), and classrooms (113-115). Because of the results of numerous
studies (116-120) and the experiences of TB clinicians and
mycobacteriologists during the past several decades, the use of UVGI has been
recommended as a supplement to other TB infection-control measures in
settings where the need for killing or inactivating tubercle bacilli is
important (2,4,121-125). (For Figure S3-7, see printed copy) UV radiation is defined as that portion of
the electromagnetic spectrum described by wavelengths from 100 to 400 nm. For
convenience of classification, the UV spectrum has been separated into three
different wave-length bands: UV-A (long wavelengths, range: 320-400 nm), UV-B
(midrange wavelengths, range: 290-320 nm), and UV-C (short wavelengths,
range: 100-290 nm) (126). Commercially available UV lamps used for germicidal
purposes are low-pressure mercury vapor lamps (127) that emit radiant energy
in the UV-C range, predominantly at a wavelength of 253.7 nm (128). A.
Applications UVGI can be used as a method of air disinfection to
supplement other engineering controls. Two systems of UVGI can be used for
this purpose: duct irradiation and upper-room air irradiation. 1. Duct
irradiation Purpose: To inactivate tubercle bacilli without exposing
persons to UVGI. In duct irradiation systems, UV lamps are placed inside
ducts that remove air from rooms to disinfect the air before it is
recirculated. When UVGI duct systems are properly designed, installed, and
maintained, high levels of UV radiation may be produced in the duct work. The
only potential for human exposure to this radiation occurs during maintenance
operations. Duct irradiation may be used: * In a TB isolation room or
treatment room to recirculate air from the room, through a duct containing UV
lamps, and back into the room. This recirculation method can increase the
overall room airflow but does not increase the supply of fresh outside air to
the room. * In other patients' rooms and in waiting rooms, emergency rooms,
and other general-use areas of a facility where patients with undiagnosed TB
could potentially contaminate the air, to recirculate air back into the
general ventilation. Duct-irradiation systems are dependent on airflow
patterns within a room that ensure that all or nearly all of the room air
circulates through the duct. 2. Upper-room air irradiation Purpose: To
inactivate tubercle bacilli in the upper part of the room, while minimizing
radiation exposure to persons in the lower part of the room. In upper-room
air irradiation, UVGI lamps are suspended from the ceiling or mounted on the
wall. The bottom of the lamp is shielded to direct the radiation upward but
not downward. The system depends on air mixing to take irradiated air from
the upper to the lower part of the room, and nonirradiated air from the lower
to the upper part. The irradiated air space is much larger than that in a
duct system. UVGI has been effective in killing bacteria under conditions
where air mixing was accomplished mainly by convection. For example, BCG was
atomized in a room that did not have supplemental ventilation (120), and in
another study a surrogate bacteria, Serratia marcesens, was aerosolized in a
room with a ventilation rate of 6 ACH (129). These reports estimated the
effect of UVGI to be equivalent to 10 and 39 ACH, respectively, for the
organisms tested, which are less resistant to UVGI than M. tuberculosis
(120). The addition of fans or some heating/air conditioning arrangements may
double the effectiveness of UVGI lamps (130-132). Greater rates of
ventilation, however, may decrease the length of time the air is irradiated,
thus decreasing the killing of bacteria (117,129). The optimal relationship
between ventilation and UVGI is not known. Air irradiation lamps used in
corridors have been effective in killing atomized S. marcesens (133). Use of
UVGI lamps in an outpatient room has reduced culturable airborne bacteria by
14%-19%. However, the irradiation did not reduce the concentration of
gram-positive, rod-shaped bacteria; although fast-growing mycobacteria were
cultured, M. tuberculosis could not be recovered from the room's air samples
because of fungal over-growth of media plates (134). Upper-room air UVGI irradiation may be used: * In isolation or treatment rooms as a supplemental
method of air cleaning. * In other patients' rooms and in waiting rooms,
emergency rooms, corridors, and other central areas of a facility where
patients with undiagnosed TB could potentially contaminate the air. Determinants
of UVGI effectiveness include room configuration, UV lamp placement, and the
adequacy of airflow patterns in bringing contaminated air into contact with
the irradiated upper-room space. Air mixing may be facilitated by supplying
cool air near the ceiling in rooms where warmer air (or a heating device) is
present below. The ceiling should be high enough for a large volume of
upper-room air to be irradiated without HCWs and patients being overexposed
to UV radiation. B. Limitations Because the clinical effectiveness of
UV systems varies, and because of the risk for transmission of M.
tuberculosis if a system malfunctions or is maintained improperly, UVGI is
not recommended for the following specific applications: 1. Duct systems
using UVGI are not recommended as a substitute for HEPA filters if air from
isolation rooms must be recirculated to other areas of a facility. 2. UVGI
alone is not recommended as a substitute for HEPA filtration or local exhaust
of air to the outside from booths, tents, or hoods used for cough-inducing
procedures. 3. UVGI is not a substitute for negative
pressure. The use of UV lamps and HEPA filtration in a
single unit would not be expected to have any infection-control benefits not
provided by use of the HEPA filter alone. The effectiveness of UVGI in killing
airborne tubercle bacilli depends on the intensity of UVGI, the duration of
contact the organism has with the irradiation, and the relative humidity
(66,108,111). Humidity can have an adverse effect on UVGI effectiveness at
levels greater than 70% relative humidity for S. marcescens (135). The
interaction of these factors has not been fully defined, however, making
precise recommendations for individual UVGI installations difficult to
develop. Old lamps or dust-covered UV lamps are less effective; therefore,
regular maintenance of UVGI systems is crucial. C. Safety Issues
Short-term overexposure to UV radiation can cause erythema and
keratoconjunctivitis (136,137). Broad-spectrum UV radiation has been
associated with increased risk for squamous and basal cell carcinomas of the
skin (138). UV-C was recently classified by the International Agency for
Research on Cancer as "probably carcinogenic to humans (Group 2A)"
(138). This classification is based on studies suggesting that UV-C radiation
can induce skin cancers in animals; DNA damage, chromosomal aberrations and
sister chromatid exchange and transformation in human cells in vitro; and DNA
damage in mammalian skin cells in vivo. In the animal studies, a contribution
of UV-B to the tumor effects could not be excluded, but the effects were
greater than expected for UV-B alone (138). Although some recent studies have
demonstrated that UV radiation can activate HIV gene promoters (i.e., the
genes in HIV that prompt replication of the virus) in laboratory samples of
human cells (139-144), the implications of these in vitro findings for humans
are unknown. In 1972, the National Institute for Occupational Safety and
Health (NIOSH) published a recommended exposure limit (REL) for occupational
exposure to UV radiation (136). The REL is intended to protect workers from
the acute effects of UV exposure (e.g., erythema and
photokeratoconjunctivitis). However, photosensitive persons and those exposed
concomitantly to photoactive chemicals may not be protected by the recommended
standard. If proper procedures are not followed, HCWs performing maintenance
on such fixtures are at risk for exposure to UV radiation. Because UV
fixtures used for upper-room air irradiation are present in rooms, rather
than hidden in ducts, safety may be much more difficult to achieve and
maintain. Fixtures must be designed and installed to ensure that UV exposure
to persons in the room (including HCWs and inpatients) are below current safe
exposure levels. Recent health hazard evaluations conducted by CDC have noted
problems withover-exposure of HCWs to UVGI and with inadequate maintenance,
training, labelling, and use of personal protective equipment (145-147). The
current number of persons who are properly trained in UVGI system design and
installation is limited. CDC strongly recommends that a competent UVGI system
designer be consulted to address safety considerations before such a system
is procured and installed. Experts who might be consulted include industrial
hygienists, engineers, and health physicists. Principles for the safe
installation of UV lamp fixtures have been developed and can be used as
guidelines (148,149). If UV lamps are being used in a facility, the general
TB education of HCWs should include: 1. The basic principles of UVGI systems
(i.e., how they work and what their limitations are). 2. The potential
hazardous effects of UVGI if overexposure occurs. 3. The potential for
photosensitivity associated with certain medical conditions or use of some
medications. 4. The importance of general maintenance procedures for UVGI
fixtures. Exposure to UV intensities above the REL should be avoided. Lightweight
clothing made of tightly woven fabric and UV-absorbing sunscreens with
solar-protection factors (SPFs) greater than or equal to 15 may help protect
photosensitive persons. HCWs should be advised that any eye or skin
irritation that develops after UV exposure should be examined by occupational
health staff. D. Exposure Criteria for UV Radiation The NIOSH REL for
UV radiation is wavelength dependent because different wavelengths of UV
radiation have different adverse effects on the skin and eyes (136). Relative
spectral effectiveness (S lambda) is used to compare various UV sources with
a source producing UV radiation at 270 nm, the wavelength of maximum ocular
sensitivity. For example, the S lambda at 254 nm is 0.5; therefore, twice as
much energy is required at 254 nm to produce an identical biologic effect at
270 nm (136). Thus, at 254 nm, the NIOSH REL is 0.006 joules per square centimeter
(J/cm(2)); and at 270 nm, it is 0.003 J/cm(2). For germicidal lamps that emit
radiant energy predominantly at a wavelength of 254 nm, proper use of the REL
requires that the measured irradiance level (E) in microwatts per square
centimeter (uW/cm(2)) be multiplied by the relative spectral effectiveness at
254 nm (0.5) to obtain the effective irradiance (E(eff)). The maximum
permissible exposure time can then be determined for selected values of
E(eff) (Table S3-3), or it can be calculated (in seconds) by dividing 0.003
J/cm(2) (the NIOSH REL at 270 nm) by E(eff) in uW/cm(2) (136,150). To protect
HCWs who are exposed to germicidal UV radiation for 8 hours per workday, the
measured irradiance (E) should be less than or equal to 0.2 uW/cm(2). This is
calculated by obtaining If (0.1 uW/cm(2)) (Table S3-3) and then dividing this
value by S lambda (0.5). E. Maintenance and Monitoring 1. Labelling
and posting Warning signs should be posted on UV lamps and wherever
high-intensity (i.e., UV exposure greater than the REL) germicidal UV
irradiation is present (e.g., upper-room air space and accesses to ducts [if
duct irradiation is used]) to alert maintenance staff or other HCWs of the
hazard. Some examples are shown below: (For Table S3-3, see printed copy) CAUTION | | CAUTION | | ULTRAVIOLET ENERGY: |
| | |TURN OFF LAMPS BEFORE | | ULTRAVIOLET ENERGY: | | ENTERING UPPER ROOM |
| PROTECT EYES & SKIN | 2. Maintenance Because the intensity of UV lamps fluctuates
as they age, a schedule for replacing the lamps should be developed. The
schedule can be determined from either a time/use log or a system based on
cumulative time. The tube should be checked periodically for dust build-up,
which lessens the output of UVGI. If the tube is dirty, it should be allowed
to cool, then cleaned with a damp cloth. Tubes should be replaced if they
stop glowing or if they flicker to an objectionable extent. Maintenance
personnel must turn off all UV tubes before entering the upper part of the
room or before accessing ducts for any purpose. Only a few seconds of direct
exposure to the intense UV radiation in the upper-room air space or in ducts
can cause burns. Protective equipment (e.g., gloves and goggles [and/or face
shields]) should be worn if exposure greater than the recommended standard is
anticipated. Banks of UVGI tubes can be installed in ventilating ducts. Safety
devices should be used on access doors to eliminate hazard to maintenance
personnel. For duct irradiation systems, the access door for servicing the
lamps should have an inspection window* through which the lamps are checked
periodically for dust build-up and malfunctioning. The access door should
have a warning sign written in languages appropriate for maintenance
personnel to alert them to the health hazard of looking directly at bare
tubes. The lock for this door should have an automatic electric switch or
other device that turns off the lamps when the door is opened. __________ *
Ordinary glass (not quartz) is sufficient to filter out UV radiation. Two types of fixtures are used in upper-room
air irradiation: wall-mounted fixtures that have louvers to block downward
radiation and ceiling-mounted fixtures that have baffles to block radiation
below the horizontal plane of the UV tube. The actual UV tube in either type
of fixture must not be visible from any normal position in the room. Light
switches that can be locked should be used, if possible, to prevent injury to
personnel who might unintentionally turn the lamps on during maintenance
procedures. In most applications, properly shielding the UV lamps to provide
protection from most, if not all, of the direct UV radiation is not
difficult. However, radiation reflected from glass, polished metal, and
high-gloss ceramic paints can be harmful to persons in the room, particularly
if more than one UV lamp is in use. Surfaces in irradiated rooms that can
reflect UVGI into occupied areas of the room should be covered with non-UV
reflecting material. 3. Monitoring A regularly scheduled evaluation of
the UV intensity to which HCWs, patients, and others are exposed should be
conducted. UV measurements should be made in various locations within a room
using a detector designed to be most sensitive at 254 nm. Equipment used to
measure germicidal UV radiation should be maintained and calibrated on a
regular schedule. A new UV installation must be carefully checked for hot
spots (i.e., areas of the room where the REL is exceeded) by an industrial
hygienist or other person knowledgeable in making UV measurements. UV
radiation levels should not exceed those in the recommended guidelines. Supplement 4: Respiratory Protection I. Considerations for Selection of Respirators Personal respiratory protection should be
used by a) persons entering rooms where patients with known or suspected
infectious TB are being isolated, b) persons present during cough-inducing or
aerosol-generating procedures performed on such patients, and c) persons in
other settings where administrative and engineering controls are not likely
to protect them from inhaling infectious airborne droplet nuclei. These other
settings should be identified on the basis of the facility's risk assessment.
Although data regarding the effectiveness of respiratory protection from many
hazardous airborne materials have been collected, the precise level of
effectiveness in protecting HCWs from M. tuberculosis transmission in
health-care settings has not been determined. Information concerning the
transmission of M. tuberculosis is incomplete. Neither the smallest
infectious dose of M. tuberculosis nor the highest level of exposure to M.
tuberculosis at which transmission will not occur has been defined
conclusively (59,151,152). Furthermore, the size distribution of droplet
nuclei and the number of particles containing viable M. tuberculosis that are
expelled by infectious TB patients have not been defined adequately, and
accurate methods of measuring the concentration of infectious droplet nuclei
in a room have not been developed. Nevertheless, in certain settings the
administrative and engineering controls may not adequately protect HCWs from
airborne droplet nuclei (e.g., in TB isolation rooms, treatment rooms in
which cough-inducing or aerosol-generating procedures are performed, and
ambulances during the transport of infectious TB patients). Respiratory
protective devices used in these settings should have characteristics that
are suitable for the organism they are protecting against and the settings in
which they are used. A. Performance Criteria for Personal Respirators for
Protection Against Transmission of M. tuberculosis Respiratory protective
devices used in health-care settings for protection against M. tuberculosis
should meet the following standard criteria. These criteria are based on
currently available information, including a) data on the effectiveness of
respiratory protection against noninfectious hazardous materials in
workplaces other than health-care settings and on an interpretation of how
these data can be applied to respiratory protection against M. tuberculosis;
b) data on the efficiency of respirator filters in filtering biological
aerosols; c) data on face-seal leakage; and d) data on the characteristics of
respirators that were used in conjunction with administrative and engineering
controls in outbreak settings where transmission to HCWs and patients was
terminated. 1. The ability to filter particles 1 um in size in the unloaded
state with a filter efficiency of greater than or equal to 95% (i.e., filter
leakage of less than or equal to 5%), given flow rates of up to 50 L per
minute. Available data suggest that infectious droplet nuclei range in size
from 1 um to 5 um; therefore, respirators used in health-care settings should
be able to efficiently filter the smallest particles in this range. Fifty
liters per minute is a reasonable estimate of the highest airflow rate an HCW
is likely to achieve during breathing, even while performing strenuous work
activities. 2. The ability to be qualitatively or quantitatively fit tested
in a reliable way to obtain a face-seal leakage of less than or equal to 10%
(54,55). 3. The ability to fit the different facial sizes and characteristics
of HCWs, which can usually be met by making the respirators available in at
least three sizes. 4. The ability to be checked for facepiece fit, in
accordance with OSHA standards and good industrial hygiene practice, by HCWs
each time they put on their respirators (54,55). In some settings, HCWs may
be at risk for two types of exposure: a) inhalation of M. tuberculosis and b)
mucous membrane exposure to fluids that may contain bloodborne pathogens. In
these settings, protection against both types of exposure should be used. When
operative procedures (or other procedures requiring a sterile field) are
performed on patients who may have infectious TB, respiratory protection worn
by the HCW should serve two functions: a) it should protect the surgical
field from the respiratory secretions of the HCW and b) it should protect the
HCW from infectious droplet nuclei that may be expelled by the patient or
generated by the procedure. Respirators with expiration valves and
positive-pressure respirators do not protect the sterile field; therefore, a
respirator that does not have a valve and that meets the criteria in
Supplement 4, Section I.A, should be used. B. Specific Respirators The
OSHA respiratory protection standard requires that all respiratory protective
devices used in the workplace be certified by NIOSH.* NIOSH-approved HEPA
respirators are the only currently available air-purifying respirators that
meet or exceed the standard performance criteria stated above. However, the
NIOSH certification procedures are currently being revised (153). Under the
proposed revision, filter materials would be tested at a flow rate of 85
L/min for penetration by particles with a median aerodynamic diameter of 0.3
um and, if certified, would be placed in one of the following categories:
type A, which has greater than or equal to 99.97% efficiency (similar to
current HEPA filter media); type B, greater than or equal to 99% efficiency;
or type C, greater than or equal to 95% efficiency. According to this
proposed scheme, type C filter material would meet or exceed the standard
performance criteria specified in this document. __________ *
29 CFR Part 1910.134. The facility's risk assessment may identify a
limited number of selected settings (e.g., bronchoscopy performed on patients
suspected of having TB or autopsy performed on deceased persons suspected of
having had active TB at the time of death) where the estimated risk for
transmission of M. tuberculosis may be such that a level of respiratory
protection exceeding the standard criteria is appropriate. In such circumstances,
a level of respiratory protection exceeding the standard criteria and
compatible with patient-care delivery (e.g., negative-pressure respirators
that are more protective; powered air-purifying particulate respirators
[PAPRs]; or positive-pressure airline, half-mask respirators) should be
provided by employers to HCWs who are exposed to M. tuberculosis. Information
on these and other respirators may be found in the NIOSH Guide to Industrial
Respiratory Protection (55). C. The Effectiveness of Respiratory
Protective Devices The following information, which is based on
experience with respiratory protection in the industrial setting, summarizes
the available data about the effectiveness of respiratory protection against
hazardous airborne materials. Data regarding protection against transmission
of M. tuberculosis are not available. The parameters used to determine the
effectiveness of a respiratory protective device are face-seal efficacy and
filter efficacy. 1. Face-seal leakage Face-seal leakage compromises
the ability of particulate respirators to protect HCWs from airborne
materials (154-156). A proper seal between the respirator's sealing surface
and the face of the person wearing the respirator is essential for effective
and reliable performance of any negative-pressure respirator. This seal is
less critical, but still important, for positive-pressure respirators. Face-seal
leakage can result from various factors, including incorrect facepiece size
or shape, incorrect or defective facepiece sealing-lip, beard growth,
perspiration or facial oils that can cause facepiece slippage, failure to use
all the head straps, incorrect positioning of the facepiece on the face,
incorrect head strap tension or position, improper respirator maintenance,
and respirator damage. Every time a person wearing a negative-pressure
particulate respirator inhales, a negative pressure (relative to the
workplace air) is created inside the facepiece. Because of this negative
pressure, air containing contaminants can take a path of least resistance
into the respirator -- through leaks at the face-seal interface -- thus
avoiding the higher-resistance filter material. Currently available,
cup-shaped, disposable particulate respirators have from 0 to 20% face-seal
leakage (55,154). This face-seal leakage results from the variability of the
human face and from limitations in the respirator's design, construction, and
number of sizes available. The face-seal leakage is probably higher if the
respirator is not fitted properly to the HCW's face, tested for an adequate
fit by a qualified person, and then checked for fit by the HCW every time the
respirator is put on. Face-seal leakage may be reduced to less than 10% with
improvements in design, a greater variety in available sizes, and appropriate
fit testing and fit checking. In comparison with negative-pressure
respirators, positive-pressure respirators produce a positive pressure inside
the facepiece under most conditions of use. For example, in a PAPR, a blower
forcibly draws ambient air through HEPA filters, then delivers the filtered
air to the facepiece. This air is blown into the facepiece at flow rates that
generally exceed the expected inhalation flow rates. The positive pressure
inside the facepiece reduces face-seal leakage to low levels, particularly
during the relatively low inhalation rates expected in health-care settings. PAPRs
with a tight-fitting facepiece have less than 2% face-seal leakage under
routine conditions (55). Powered-air respirators with loose-fitting facepieces,
hoods, or helmets have less than 4% face-seal leakage under routine
conditions (55). Thus, a PAPR may offer lower levels of face-seal leakage
than nonpowered, half-mask respirators. Full facepiece, nonpowered
respirators have the same leakage (i.e., less than 2%) as PAPRs. Another
factor contributing to face-seal leakage of cup-shaped, disposable
respirators is that some of these respirators are available in only one size.
A single size may produce higher leakage for persons who have smaller or difficult-to-fit
faces (157). The facepieces used for some reusable (including HEPA and
replaceable filter, negative-pressure) and all positive-pressure particulate
air-purifying respirators are available in as many as three different sizes. 2.
Filter leakage Aerosol leakage through respirator filters depends on at
least five independent variables: a) the filtration characteristics for each
type of filter, b) the size distribution of the droplets in the aerosol, c)
the linear velocity through the filtering material, d) the filter loading
(i.e., the amount of contaminant deposited on the filter), and e) any
electrostatic charges on the filter and on the droplets in the aerosol (158).
When HEPA filters are used in particulate air-purifying respirators, filter
efficiency is so high (i.e., effectively 100%) that filter leakage is not a
consideration. Therefore, for all HEPA-filter respirators, virtually all
inward leakage of droplet nuclei occurs at the respirator's face seal. 3.
Fit testing Fit testing is part of the respiratory protection program
required by OSHA for all respiratory protective devices used in the
workplace. A fit test determines whether a respiratory protective device
adequately fits a particular HCW. The HCW may need to be fit tested with
several devices to determine which device offers the best fit. However, fit
tests can detect only the leakage that occurs at the time of the fit testing,
and the tests cannot distinguish face-seal leakage from filter leakage. Determination
of facepiece fit can involve qualitative or quantitative tests (55). A
qualitative test relies on the subjective response of the HCW being fit
tested. A quantitative test uses detectors to measure inward leakage. Disposable,
negative-pressure particulate respirators can be qualitatively fit tested
with aerosolized substances that can be tasted, although the results of this
testing are limited because the tests depend on the subjective response of
the HCW being tested. Quantitative fit testing of disposable
negative-pressure particulate respirators can best be performed if the
manufacturer provides a test respirator with a probe for this purpose. Replaceable
filter, negative-pressure particulate respirators and all positive-pressure
particulate respirators can be fit tested reliably, both qualitatively and
quantitatively, when fitted with HEPA filters. 4. Fit checking A fit
check is a maneuver that an HCW performs before each use of the respiratory
protective device to check the fit. The fit check can be performed according
to the manufacturer's facepiece fitting instructions by using the applicable
negative-pressure or positive-pressure test. Some currently available
cup-shaped, disposable negative-pressure particulate respirators cannot be
fit checked reliably by persons wearing the devices because occluding the
entire surface of the filter is difficult. Strategies for overcoming these
limitations are being developed by respirator manufacturers. 5. Reuse of
respirators Conscientious respirator maintenance should be an integral
part of an overall respirator program. This maintenance applies both to
respirators with replaceable filters and respirators that are classified as
disposable but that are reused. Manufacturers' instructions for inspecting,
cleaning, and maintaining respirators should be followed to ensure that the
respirator continues to function properly (55). When respirators are used for
protection against noninfectious aerosols (e.g., wood dust), which may be
present in the air in heavy concentrations, the filter material may become
occluded with airborne material. This occlusion may result in an
uncomfortable breathing resistance. In health-care settings where respirators
are used for protection against biological aerosols, the concentration of
infectious particles in the air is probably low; thus, the filter material in
a respirator is very unlikely to become occluded with airborne material. In
addition, there is no evidence that particles impacting on the filter
material in a respirator are re-aerosolized easily. For these reasons, the
filter material used in respirators in the health-care setting should remain
functional for weeks to months. Respirators with replaceable filters are
reusable, and a respirator classified as disposable may be reused by the same
HCW as long as it remains functional. Before each use, the outside of the
filter material should be inspected. If the filter material is physically
damaged or soiled, the filter should be changed (in the case of respirators
with replaceable filters) or the respirator discarded (in the case of
disposable respirators). Infection-control personnel should develop standard
operating procedures for storing, reusing, and disposing of respirators that
have been designated as disposable and for disposing of replaceable filter
elements. II. Implementing a Personal Respiratory Protection Program If personal respiratory protection is used in
a health-care setting, OSHA requires that an effective personal respiratory
protection program be developed, implemented, administered, and periodically
reevaluated (54,55). All HCWs who need to use respirators for protection
against infection with M. tuberculosis should be included in the respiratory
protection program. Visitors to TB patients should be given respirators to
wear while in isolation rooms, and they should be given general instructions
on how to use their respirators. The number of HCWs included in the
respiratory protection program in each facility will vary depending on a) the
number of potentially infectious TB patients, b) the number of rooms or areas
to which patients with suspected or confirmed infectious TB are admitted, and
c) the number of HCWs needed in these rooms or areas. Where respiratory
protection programs are required, they should include enough HCWs to provide
adequate care for a patient with known or suspected TB should such a patient
be admitted to the facility. However, administrative measures should be used
to limit the number of HCWs who need to enter these rooms or areas, thus
limiting the number of HCWs who need to be included in the respiratory
protection program. Information regarding the development and management of a
respiratory protection program is available in technical training courses
that cover the basics of personal respiratory protection. Such courses are
offered by various organizations, such as NIOSH, OSHA, and the American
Industrial Hygiene Association. Similar courses are available from private
contractors and universities. To be effective and reliable, respiratory
protection programs must contain at least the following elements (55,154): 1.
Assignment of responsibility. Supervisory responsibility for the respiratory
protection program should be assigned to designated persons who have
expertise in issues relevant to the program, including infectious diseases
and occupational health. 2. Standard operating procedures. Written standard
operating procedures should contain information concerning all aspects of the
respiratory protection program. 3. Medical screening. HCWs should not be
assigned a task requiring use of respirators unless they are physically able
to perform the task while wearing the respirator. HCWs should be screened for
pertinent medical conditions at the time they are hired, then rescreened
periodically (55). The screening could occur as infrequently as every 5
years. The screening process should begin with a general screening (e.g., a
questionnaire) for pertinent medical conditions, and the results of the
screening should then be used to identify HCWs who need further evaluation. Routine
physical examination or testing with chest radiographs or spirometry is not
necessary or required. Few medical conditions preclude the use of most
negative-pressure particulate respirators. HCWs who have mild pulmonary or
cardiac conditions may report discomfort with breathing when wearing
negative-pressure particulate respirators, but these respirators are unlikely
to have adverse health effects on the HCWs. Those HCWs who have more severe
cardiac or pulmonary conditions may have more difficulty than HCWs with
similar but milder conditions if performing duties while wearing
negative-pressure respirators. Furthermore, these HCWs may be unable to use
some PAPRs because of the added weight of these respirators. 4. Training.
HCWs who wear respirators and the persons who supervise them should be
informed about the necessity for wearing respirators and the potential risks
associated with not doing so. This training should also include at a minimum:
* The nature, extent, and specific hazards of M. tuberculosis transmission in
their respective health-care facility. * A description of specific risks for
TB infection among persons exposed to M. tuberculosis, of any subsequent
treatment with INH or other chemoprophylactic agents, and of the possibility
of active TB disease. * A description of engineering controls and work
practices and the reasons why they do not eliminate the need for personal
respiratory protection. * An explanation for selecting a particular type of
respirator, how the respirator is properly maintained and stored, and the
operation, capabilities, and limitations of the respirator provided. *
Instruction in how the HCW wearing the respirator should inspect, put on, fit
check, and correctly wear the provided respirator (i.e., achieve and maintain
proper face-seal fit on the HCW's face). * An opportunity to handle the
provided respirator and learn how to put it on, wear it properly, and check
the important parts. * Instruction in how to recognize an inadequately
functioning respirator. 5. Face-seal fit testing and fit checking. HCWs
should undergo fit testing to identify a respirator that adequately fits each
individual HCW. The HCW should receive fitting instructions that include
demonstrations and practice in how the respirator should be worn, how it should
be adjusted, and how to determine if it fits properly. The HCW should be
taught to check the facepiece fit before each use. 6. Respirator inspection,
cleaning, maintenance, and storage. Conscientious respirator maintenance
should be an integral part of an overall respirator program. This maintenance
applies both to respirators with replaceable filters and respirators that are
classified as disposable but that are reused. Manufacturers' instructions for
inspecting, cleaning, and maintaining respirators should be followed to
ensure that the respirator continues to function properly (55). 7. Periodic
evaluation of the personal respiratory protection program. The program should
be evaluated completely at least once a year, and both the written operating
procedures and program administration should be revised as necessary based on
the results of the evaluation. Elements of the program that should be
evaluated include work practices and employee acceptance of respirator use
(i.e., subjective comments made by employees concerning comfort during use
and interference with duties). Supplement 5: Decontamination -- Cleaning, Disinfecting, and Sterilizing of Patient-Care
Equipment Equipment
used on patients who have TB is usually not involved in the transmission of
M. tuberculosis, although transmission by contaminated bronchoscopes has been
demonstrated (159,160). Guidelines for cleaning, disinfecting, and
sterilizing equipment have been published (161,162). The rationale for
cleaning, disinfecting, or sterilizing patient-care equipment can be
understood more readily if medical devices, equipment, and surgical materials
are divided into three general categories. These categories -- critical,
semicritical, and noncritical items -- are defined by the potential risk for
infection associated with their use (163,164). Critical
items are instruments that are introduced directly into the bloodstream or
into other normally sterile areas of the body (e.g., needles, surgical
instruments, cardiac catheters, and implants). These items should be sterile
at the time of use. Semicritical
items are those that may come in contact with mucous membranes but do not
ordinarily penetrate body surfaces (e.g., noninvasive flexible and rigid
fiberoptic endoscopes or bronchoscopes, endotracheal tubes, and anesthesia
breathing circuits). Although sterilization is preferred for these
instruments, high-level disinfection that destroys vegetative microorganisms,
most fungal spores, tubercle bacilli, and small nonlipid viruses may be used.
Meticulous physical cleaning of such items before sterilization or high-level
disinfection is essential. Noncritical
items are those that either do not ordinarily touch the patient or touch only
the patient's intact skin (e.g., crutches, bedboards, blood pressure cuffs,
and various other medical accessories). These items are not associated with
direct transmission of M. tuberculosis, and washing them with detergent is
usually sufficient. Health-care
facility policies should specify whether cleaning, disinfecting, or
sterilizing an item is necessary to decrease the risk for infection. Decisions
about decontamination processes should be based on the intended use of the
item, not on the diagnosis of the patient for whom the item was used. Selection
of chemical disinfectants depends on the intended use, the level of
disinfection required, and the structure and material of the item to be
disinfected. Although
microorganisms are ordinarily found on walls, floors, and other environmental
surfaces, these surfaces are rarely associated with transmission of
infections to patients or HCWs. This is particularly true with organisms such
as M. tuberculosis, which generally require inhalation by the host for
infection to occur. Therefore, extraordinary attempts to disinfect or
sterilize environmental surfaces are not indicated. If a detergent germicide
is used for routine cleaning, a hospital-grade, EPA-approved
germicide/disinfectant that is not tuberculocidal can be used. The same
routine daily cleaning procedures used in other rooms in the facility should
be used to clean TB isolation rooms, and personnel should follow isolation
practices while cleaning these rooms. For final cleaning of the isolation
room after a patient has been discharged, personal protective equipment is not
necessary if the room has been ventilated for the appropriate amount of time
(Table S3-1). References 1. CDC. National action plan to combat
multidrug-resistant tuberculosis. Atlanta: US Department of Health and Human
Services, Public Health Service, CDC, 1992. 2. CDC. Guidelines for preventing
the transmission of tuberculosis in health-care settings, with special focus
on HIV-related issues. MMWR 1990;39(No. RR-17). 3. CDC. Draft guidelines for
preventing the transmission of tuberculosis in health-care facilities, second
edition; notice of comment period. Federal Register 1993;58:52810-54. 4. CDC.
Guidelines for prevention of TB transmission in hospitals. Atlanta: US
Department of Health and Human Services, Public Health Service, CDC, 1982;
DHHS publication no. (CDC)82-8371. 5. CDC. Screening for tuberculosis and
tuberculous infection in high-risk populations, and the use of preventive
therapy for tuberculous infection in the United States: recommendations of
the Advisory Committee for Elimination of Tuberculosis. MMWR 1990;39(No.
RR-8). 6. American Thoracic Society/CDC. Diagnostic standards and
classification of tuberculosis. Am Rev Respir Dis 1990;142:725-35. 7. Wells
WF. Aerodynamics of droplet nuclei. In: Airborne contagion and air hygiene. Cambridge:
Harvard University Press, 1955:13-9. 8. Selwyn PA, Hartel D, Lewis VA, et al. A prospective study of the risk of
tuberculosis among intravenous drug users with human immunodeficiency virus
infection. N Engl J Med 1989;320:545-50. 9. Di Perri G, Cruciani M,
Danzi MC, et al. Nosocomial
epidemic of active tuberculosis among HIV-infected patients. Lancet
1989;2:1502-4. 10.
Daley CL, Small PM, Schecter GF, et al. An outbreak of tuberculosis with
accelerated progression among persons infected with the human immunodeficiency
virus: an analysis using restriction-fragment-length polymorphisms. N Engl J
Med 1992;326:231-5. 11.
Edlin BR, Tokars JI, Grieco MH, et al. An outbreak of multidrug-resistant
tuberculosis among hospitalized patients with the acquired immunodeficiency
syndrome. N Engl J Med 1992;326:1514-21. 12.
Dooley SW, Villarino E, Lawrence M, et al. Nosocomial transmission of
tuberculosis in a hospital unit for HIV-infected patients. JAMA 1992; 267:2632-4. 13.
Ten Dam HG. Research
on BCG vaccination. Adv Tuberc Res 1984;21:79-106. 14.
Barrett-Connor E. The epidemiology of tuberculosis in physicians. JAMA 1979;241:33-8. 15.
Brennen C, Muder RR, Muraca PW. Occult endemic tuberculosis in a chronic care facility. Infect Control
Hosp Epidemiol 1988;9:548-52. 16.
Goldman KP. Tuberculosis in hospital doctors. Tubercle 1988;69:237-40.
17. Catanzaro A. Nosocomial tuberculosis. Am Rev Respir Dis 1982;125:559-62. 18.
Ehrenkranz NJ, Kicklighter JL. Tuberculosis outbreak in a general hospital: evidence of airborne
spread of infection. Ann
Intern Med 1972; 77:377-82. 19.
Haley CE, McDonald RC, Rossi L, et al. Tuberculosis epidemic among hospital
personnel. Infect Control Hosp Epidemiol 1989;10:204-10. 20.
Hutton MD, Stead WW, Cauthen GM, et al. Nosocomial transmission of
tuberculosis associated with a draining tuberculous abscess. J Infect Dis 1990;161:286-95. 21. Kantor HS, Poblete R, Pusateri SL. Nosocomial transmission of
tuberculosis from unsuspected disease. Am J Med 1988;84:833-8. 22.
Lundgren R, Norrman E, Asberg I. Tuberculous infection transmitted at
autopsy. Tubercle 1987;68:147-50. 23.
CDC. Mycobacterium tuberculosis transmission in a health clinic -- Florida,
1988. MMWR 1989;38:256-8,263-4. 24.
Beck-Sague C, Dooley SW, Hutton MD, et al. Outbreak of multidrug-resistant
Mycobacterium tuberculosis infections in a hospital: transmission to patients
with HIV infection and staff. JAMA 1992;268:1280-6. 25.
CDC. Nosocomial transmission of multidrug-resistant tuberculosis to
health-care workers and HIV-infected patients in an urban hospital --
Florida. MMWR 1990;39:718-22. 26.
CDC. Nosocomial transmission of multidrug-resistant tuberculosis among
HIV-infected persons -- Florida and New York, 1988-1991. MMWR 1991; 40:585-91. 27.
Pearson ML, Jereb JA, Frieden TR, et al. Nosocomial transmission of
multidrug-resistant Mycobacterium tuberculosis: a risk to patients and health
care workers. Ann Intern
Med 1992;117:191-6. 28.
Dooley SW, Jarvis WR, Martone WJ, Snider DE Jr. Multidrug-resistant
tuberculosis [Editorial]. Ann
Intern Med 1992;117:257-8. 29.
Wenger P, Beck-Sague C, Otten J, et al. Efficacy of control measures in
preventing nosocomial transmission of multidrug-resistant tuberculosis among
patient and health-care workers [Abstract 53A]. In: Program and abstracts of
the World Congress on Tuberculosis. Bethesda, MD: National Institutes of
Health, Fogarty International Center, 1992. 30.
Otten J, Chen J, Cleary T. Successful control of an outbreak of multi-drug-resistant
tuberculosis in an urban teaching hospital [Abstract 51D]. In: Program and
abstracts of the World Congress on Tuberculosis. Bethesda, MD: National
Institutes of Health, Fogarty International Center, 1992. 31.
Maloney S, Pearson M, Gordon M, et al. The efficacy of recommended infection
control measures in preventing nosocomial transmission of multidrug-resistant
TB [Abstract 51C]. In: Program and abstracts of the World Congress on
Tuberculosis. Bethesda, MD: National Institutes of Health, Fogarty
International Center, 1992. 32.
Stroud L, Tokars J, Grieco M, Gilligan M, Jarvis W. Interruption of
nosocomial transmission of multidrug-resistant Mycobacterium tuberculosis
(MDR-TB) among AIDS patients in a New York City Hospital [Abstract A1-3]. In:
Third Annual Meeting of the Society for Hospital Epidemiologists of America. Chicago:
Society for Hospital Epidemiologists of America, 1993. 33.
American Thoracic Society. Treatment of tuberculosis and tuberculosis
infection in adults and children. Am J Respir Crit Care Med 1994;149:
1359-74. 34.
Strong BE, Kubica GP. Isolation and identification of Mycobacterium
tuberculosis. Atlanta: US Department of Health and Human Services, Public
Health Service, CDC, 1981; DHHS publication no. (CDC)81-8390. 35.
CDC. Tuberculosis and human immunodeficiency virus infection: recommendations
of the Advisory Committee for the Elimination of Tuberculosis (ACET). MMWR 1989;38:236-8,243-50. 36.
Willcox PA, Benator SR, Potgieter PD. Use of flexible fiberoptic bronchoscope in
diagnosis of sputum-negative pulmonary tuberculosis. Thorax 1982;37:598-601. 37.
Willcox PA, Potgieter PD, Bateman ED, Benator SR. Rapid diagnosis of
sputum-negative miliary tuberculosis using the flexible fiberoptic
bronchoscope. Thorax 1986;41:681-4. 38.
Tenover FC, Crawford JT, Huebner RE, Geiter LJ, Horsburgh CR Jr, Good RC. The
resurgence of tuberculosis: is your laboratory ready? J Clin Microbiol
1993;31:767-70. 39.
Pitchenik AE, Cole C, Russell BW, et al. Tuberculosis, atypical mycobacteriosis,
and the acquired immunodeficiency syndrome among Haitian and non-Haitian
patients in South Florida. Ann Intern Med 1984;101:641-5. 40.
Maayan S, Wormser GP, Hewlett D, et al. Acquired immunodeficiency syndrome
(AIDS) in an economically disadvantaged population. Arch Intern Med 1985;145:1607-12. 41.
Klein NC, Duncanson FP, Lenox TH III, et al. Use of mycobacterial smears in
the diagnosis of pulmonary tuberculosis in AIDS/ARC patients. Chest
1989;95:1190-2. 42.
Burnens AP, Vurma-Rapp U. Mixed mycobacterial cultures -- occurrence in the
clinical laboratory. Int J Med Microbiol 1989;27:85-90. 43.
CDC. Initial therapy for tuberculosis in the era of multidrug resistance:
recommendations of the Advisory Council for the Elimination of Tuberculosis. MMWR
1993;42(No. RR-7). 44.
Rabalais G, Adams G, Stover B. PPD skin test conversion in health-care
workers after exposure to Mycobacterium tuberculosis infection in infants
[Letter]. Lancet 1991;338:826. 45. Wallgren A. On contagiousness of childhood tuberculosis. Acta Pediatr Scand 1937;22:229-34. 46.
Riley RL. Airborne infection. Am J Med 1974;57:466-75. 47. American Society of Heating, Refrigerating and Air-Conditioning
Engineers. Chapter 7: Health facilities. In: 1991 Application handbook. Atlanta:
American Society of Heating, Refrigerating and Air-Conditioning Engineers,
Inc., 1991. 48.
American Institute of Architects, Committee on Architecture for Health. Chapter
7: General hospital. In: Guidelines for construction and equipment of
hospital and medical facilities. Washington, DC: The American Institute of
Architects Press, 1987. 49.
Health Resources and Services Administration. Guidelines for construction and
equipment of hospital and medical facilities. Rockville, MD: US Department of
Health and Human Services, Public Health Service, 1984; PHS publication no. (HRSA)84-14500. 50.
Riley RL, O'Grady F. Airborne infection: transmission and control. New York:
McMillan, 1961. 51.
Galson E, Goddard KR. Hospital
air conditioning and sepsis control. ASHRAE Journal, 1968;(Jul):33-41. 52.
Kethley TW. Air: its importance and control. In: Proceedings of the National
Conference on Institutionally Acquired Infections. Washington, DC: US
Department of Health, Education, and Welfare, Public Health Service,
Communicable Disease Center, Division of Hospital and Medical Facilities,
1963:35-46; PHS publication no. 1188. 53.
Hermans RD, Streifel AJ. Ventilation design. In: Bierbaum PJ, Lippmann M,
eds. Proceedings of the
Workshop on Engineering Controls for Preventing Airborne Infections in
Workers in Health Care and Related Facilities. Cincinnati: US Department of
Health and Human Services, Public Health Service, CDC, 1994; DHHS publication
no. (NIOSH)94-106. 54.
American National Standards Institute. American national standard practices
for respiratory protection. New York: American National Standards Institute,
1992. 55.
NIOSH. Guide to industrial respiratory protection. Morgantown, WV: US
Department of Health and Human Services, Public Health Service, CDC, 1987;
DHHS publication no. (NIOSH)87-116. 56.
CDC. Recommendations for HIV testing services for inpatients and outpatients
in acute-care hospital settings; and Technical guidance on HIV counseling. MMWR
1993;42(No. RR-2). 57.
Williams WW. Guidelines for infection control in hospital personnel. Infect
Control 1983;4(suppl):326-49. 58.
Barrett-Connor E. The periodic chest roentgenogram for the control of
tuberculosis in health care personnel. Am Rev Respir Dis 1980;122:153-5. 59.
CDC/National Institutes of Health. Agent: Mycobacterium tuberculosis, M.
bovis. In: Biosafety in microbiological and biomedical laboratories. Atlanta:
US Department of Health and Human Services, Public Health Service, 1993:95;
DHHS publication no. (CDC)93-8395. 60.
CDC. Prevention and control of tuberculosis in facilities providing long-term
care to the elderly: recommendations of the Advisory Committee for
Elimination of Tuberculosis. MMWR 1990;39(No. RR-10). 61.
CDC. Prevention and control of tuberculosis in correctional institutions:
recommendations of the Advisory Committee for the Elimination of
Tuberculosis. MMWR 1989;38:313-20,325. 62.
Dueli RC, Madden RN. Droplet nuclei produced during dental treatment of
tubercular patients. Oral Surg 1970;30:711-6. 63.
Manoff SB, Cauthen GM, Stoneburner RL, Bloch AB, Schultz S, Snider DE Jr. TB
patients with AIDS: are they more likely to spread TB? [Abstract no. 4621].
Book 2. IV International Conference on AIDS. Stockholm, Sweden, June 12-16,
1988:216. 64.
Cauthen GM, Dooley SW, Bigler W, Burr J, Ihle W. Tuberculosis (TB)
transmission by HIV-associated TB cases [Abstract no. M.C.3326]. Vol
1. VII International
Conference on AIDS. Florence, Italy, June 16-21, 1991. 65.
Klausner JD, Ryder RW, Baende E, et al. Mycobacterium tuberculosis in
household contacts of human immunodeficiency virus type 1-seropositive
patients with active pulmonary tuberculosis in Kinshasa, Zaire. J Infect Dis 1993;168:106-11. 66.
Riley RL, Mills CC, O'Grady F, Sultan LU, Wittstadt F, Shivpuri DN. Infectiousness of air from a
tuberculosis ward. Am Rev Respir Dis 1962; 85:511-25. 67.
Noble RC. Infectiousness of pulmonary tuberculosis after starting
chemotherapy: review of the available data on an unresolved question. Am J
Infect Control 1981;9:6-10. 68.
Howard TP, Solomon DA. Reading the tuberculin skin test: who, when, and how? Arch Intern Med 1988;148:2457-9. 69.
Snider DE Jr. The
tuberculin skin test. Am
Rev Respir Dis 1982;125:108-18. 70.
Huebner RE, Schein MF, Bass JB Jr. The tuberculin skin test. Clin Infect Dis 1993;17:968-75. 71. Canessa PA, Fasano L, Lavecchia MA, Torraca
A, Schiattone ML. Tuberculin
skin test in asymptomatic HIV seropositive carriers [Letter]. Chest
1989;96:1215-6. 72.
CDC. Purified protein derivative (PPD)-tuberculin anergy and HIV infection:
guidelines for anergy testing and management of anergic persons at risk of
tuberculosis. MMWR 1991;40(No. RR-5). 73.
Snider DE, Farer LS. Package inserts for antituberculosis drugs and
tuberculins. Am Rev Respir
Dis 1985;131:809-10. 74.
Snider DE Jr. Bacille
Calmette-Guerin vaccinations and tuberculin skin test. JAMA 1985;253:3438-9. 75.
CDC. Use of BCG vaccines in the control of TB: a joint statement by the ACIP
and the Advisory Committee for the Elimination of Tuberculosis. MMWR
1988;37:663-4,669-75. 76.
Thompson NJ, Glassroth JL, Snider DE Jr, Farer LS. The booster phenomenon in
serial tuberculin testing. Am Rev Respir Dis 1979;119: 587-97. 77.
Des Prez RM, Heim CR. Mycobacterium tuberculosis. In: Mandell GL, Douglas RG
Jr, Bennett JE, eds. Principles and practice of infectious diseases. 3rd ed.
New York: Churchill Livingstone, 1990:1877-906. 78. Pitchenik AE, Rubinson HA. The radiographic appearance of tuberculosis
in patients with the acquired immune deficiency syndrome (AIDS) and pre-AIDS.
Am Rev Respir Dis 1985;131:393-6. 79.
Kiehn TE, Cammarata R. Laboratory diagnosis of mycobacterial infection in
patients with acquired immunodeficiency syndrome. J Clin Microbiol
1986;24:708-11. 80.
Crawford JT, Eisenach KD, Bates JH. Diagnosis of tuberculosis: present and
future. Semin Respir Infect
1989;4:171-81. 81.
Moulding TS, Redeker AG, Kanel GC. Twenty isoniazid-associated deaths in one state. Am Rev Respir Dis 1989;140:700-5. 82.
Snider DE Jr, Layde PM, Johnson MW, Lyle MA. Treatment of tuberculosis during pregnancy. Am
Rev Respir Dis 1980;122:65-79. 83.
Snider D. Pregnancy and tuberculosis. Chest 1984;86(suppl):10S-13S. 84.
Hamadeh MA, Glassroth J. Tuberculosis and pregnancy. Chest 1992;101: 1114-20.
85. Glassroth JL, White MC, Snider DE Jr. An assessment of the possible
association of isoniazid with human cancer deaths. Am Rev Respir Dis
1977;116:1065-74. 86.
Glassroth JL, Snider DE Jr, Comstock GW. Urinary tract cancer and isoniazid. Am
Rev Respir Dis 1977;116:331-3. 87.
Costello HD, Snider DE Jr. The incidence of cancer among participants in a
controlled, randomized isoniazid preventive therapy trial. Am J Epidemiol 1980;111:67-74. 88.
CDC. The use of preventive therapy for tuberculous infection in the United
States: recommendations of the Advisory Committee for Elimination of
Tuberculosis. MMWR 1990;39 (No. RR-8):9-12. 89.
CDC. Management of persons exposed to multidrug-resistant tuberculosis. MMWR 1992;41(No.
RR-11):59-71. 90.
American Thoracic Society/CDC. Treatment of tuberculosis and tuberculosis
infection in adults and children, 1986. Am Rev Respir Dis 1986; 134:355-63. 91.
American Thoracic Society/CDC. Control of tuberculosis in the United States. Am Rev Respir Dis 1992;146:1624-35. 92.
Snider DE Jr, Caras GJ. Isoniazid-associated hepatitis deaths: a review of available
information. Am Rev Respir Dis 1992;145:494-7. 93.
Small PM, Shafer RW, Hopewell PC, et al. Exogenous infection with multi-drug-resistant
Mycobacterium tuberculosis in patients with advanced HIV infection. N Engl J
Med 1993;328:1137-44. 94.
Iseman MD, Madsen LA. Drug-resistant
tuberculosis. Clin Chest Med 1989; 10:341-53. 95.
Goble M. Drug-resistant tuberculosis. Semin Respir Infect 1986;1:220-9. 96.
Goble M, Iseman MD, Madsen LA, Waite D, Ackerson L, Horsburgh CR Jr.
Treatment of 171 patients with pulmonary tuberculosis resistant to isoniazid
and rifampin. N Engl J Med 1993;328:527-32. 97.
Simone PM, Iseman MD. Drug-resistant tuberculosis: a deadly -- and growing --
danger. J Respir Dis
1992;13:960-71. 98.
American Conference of Governmental Industrial Hygienists. Industrial
ventilation: a manual of recommended practice. Cincinnati: American
Conference of Governmental Hygienists, Inc., 1992. 99.
Mutchler JE. Principles of ventilation. In: NIOSH. The industrial environment -- its
evaluation and control. Washington, DC: US Department of Health, Education,
and Welfare, Public Health Service, NIOSH, 1973. 100.
Sherertz RJ, Belani A, Kramer BS, et al. Impact of air filtration on
nosocomial Aspergillus infections. Am J Med 1987;83:709-18. 101.
Rhame FS, Streifel AJ, Kersey JH, McGlave PB. Extrinsic risk factors for
pneumonia in the patient at high risk of infection. Am J Med 1984;76: 42-52. 102.
Opal SM, Asp AA, Cannady PB, Morse PL, Burton LJ, Hammer PG. Efficacy of
infection control measures during a nosocomial outbreak of disseminated
Aspergillus associated with hospital construction. J Infect Dis 1986; 153:63-7. 103.
Woods JE. Cost avoidance and productivity in owning and operating buildings. Occup
Med 1989;4:753-70. 104.
Woods JE, Rask DR. Heating, ventilation, air-conditioning systems: the
engineering approach to methods of control. In: Kundsin RB, ed. Architectural design and indoor microbial
pollution. New York: Oxford University Press, 1988:123-53. 105.
American Society of Heating, Refrigerating and Air-Conditioning Engineers. Chapter
25: Air cleaners for particulate contaminants. In: 1992 Systems and equipment
fundamentals handbook. Atlanta: American Society of Heating, Refrigerating
and Air-Conditioning Engineers, Inc., 1992:25.3-25.5. 106.
American Society of Heating, Refrigerating and Air-Conditioning Engineers. Chapter
14: Air flow around buildings. In: 1989 Fundamentals handbook. Atlanta:
American Society of Heating, Refrigerating and Air-Conditioning Engineers,
Inc., 1989:14.1-14.13. 107.
Riley RL, Wells WF, Mills CC, Nyka W, McLean RL. Air hygiene in tuberculosis:
quantitative studies of infectivity and control in a pilot ward. Am Rev
Tuberc 1957;75:420-31. 108.
Riley RL, Nardell EA. Clearing the air: the theory and application of UV air
disinfection. Am Rev Respir Dis 1989;139:1286-94. 109.
Riley RL. Ultraviolet air disinfection for control of respiratory contagion. In: Kundsin RB, ed. Architectural design and indoor
microbial pollution. New York: Oxford University Press, 1988:175-97. 110.
Stead WW. Clearing the air: the theory and application of ultraviolet air
disinfection [Letter]. Am Rev Respir Dis 1989;140:1832. 111.
McLean RL. General discussion: the mechanism of spread of Asian influenza. Am
Rev Respir Dis 1961;83:36-8. 112.
Willmon TL, Hollaender A, Langmuir AD. Studies of the control of acute
respiratory diseases among naval recruits. I. A review of a four-year
experience with ultraviolet irradiation and dust suppressive measures, 1943
to 1947. Am J Hyg
1948;48:227-32. 113.
Wells WF, Wells MW, Wilder TS. The environmental control of epidemic
contagion. I. An epidemiologic study of radiant disinfection of air in day
schools. Am J Hyg
1942;35:97-121. 114.
Wells WF, Holla WA. Ventilation in the flow of measles and chickenpox through
a community: progress report, January 1, 1946 to June 15, 1949 -- Airborne
Infection Study, Westchester County Department of Health. JAMA 1950;142:1337-44. 115.
Perkins JE, Bahlke AM, Silverman HF. Effect of ultra-violet irradiation of
classrooms on spread of measles in large rural central schools. Am J Public
Health Nations Health 1947;37:529-37. 116.
Lurie MB. Resistance to tuberculosis: experimental studies in native and
acquired defensive mechanisms. Cambridge, MA: Harvard University Press,
1964:160-4. 117.
Collins FM. Relative susceptibility of acid-fast and non-acid-fast bacteria
to ultraviolet light. Appl Microbiol 1971;21:411-3. 118.
David HL, Jones WD Jr, Newman CM. Ultraviolet light inactivation and
photoreactivation in the mycobacteria. Infect Immun 1971;4:318-9. 119.
David HL. Response of mycobacteria to ultraviolet light radiation. Am Rev
Respir Dis 1973;108:1175-85. 120.
O. Riley RL, Knight M, Middlebrook G. Ultraviolet susceptibility of BCG and
virulent tubercle bacilli. Am Rev Respir Dis 1976;113:413-8. 121.
American Thoracic Society/CDC. Control of tuberculosis. Am Rev Respir Dis
1983;128:336-42. 122.
National Tuberculosis and Respiratory Disease Association. Guidelines for the
general hospital in the admission and care of tuberculous patients. Am Rev
Respir Dis 1969;99:631-3. 123.
CDC. Notes on air hygiene: summary of Conference on Air Disinfection. Arch
Environ Health 1971;22:473-4. 124.
Schieffelbein CW Jr, Snider DE Jr. Tuberculosis control among homeless populations. Arch Intern Med 1988;148:1843-6. 125.
CDC. Prevention and control of tuberculosis in correctional institutions:
recommendations of the Advisory Committee for the Elimination of
Tuberculosis. MMWR
1989;38:313-20,325. 126.
International Commission on Illumination. International lighting vocabulary [French]. 4th ed. Geneva, Switzerland: Bureau
Central de la Commission Electrotechnique Internationale, 1987; CIE
publication no. 17.4. 127.
Nagy R. Application and measurement of ultraviolet radiation. Am Ind Hyg
Assoc J 1964;25:274-81. 128.
Illuminating Engineering Society. IES lighting handbook. 4th ed. New York:
Illuminating Engineering Society, 1966:25-7. 129.
Kethley TW, Branch K. Ultraviolet lamps for room air disinfection: effect of
sampling location and particle size of bacterial aerosol. Arch Environ Health
1972;25:205-14. 130.
Riley RL, Permutt S, Kaufman JE. Convection, air mixing, and ultraviolet air disinfection in rooms. Arch
Environ Health 1971;22:200-7. 131.
Riley RL, Permutt S. Room air disinfection by ultraviolet irradiation of
upper air. Arch Environ Health 1971;22:208-19. 132.
Riley RL, Permutt S, Kaufman JE. Room air disinfection by ultraviolet irradiation of upper air: further
analysis of convective air exchange. Arch Environ Health 1971;23:35-9. 133.
Riley RL, Kaufman JE. Air
disinfection in corridors by upper air irradiation with ultraviolet. Arch
Environ Health 1971;22:551-3. 134.
Mature JM, Alevantis LE, Chang Y-L, Liu K-S. Effect of ultraviolet germicidal lamps on
airborne microorganisms in an outpatient waiting room. Applied Occupational
and Environmental Hygiene 1992;7:505-13. 135.
Riley RL, Kaufman JE. Effect of relative humidity on the inactivation of
airborne Serratia marcescens by ultraviolet radiation. Appl Microbiol
1972;23:1113-20. 136.
NIOSH. Criteria for a recommended standard...occupational exposure to
ultraviolet radiation. Washington, DC: US Department of Health, Education,
and Welfare, Public Health Service, 1972; publication no. (HSM)73-110009. 137.
Everett MA, Sayre RM, Olson RL. Physiologic response of human skin to
ultraviolet light. In: Urbach F, ed. The biologic effects of ultraviolet
radiation. Oxford, England: Pergamon Press, 1969. 138.
International Agency for Research on Cancer. IARC monographs on the
evaluation of carcinogenic risks to humans: solar and ultraviolet radiation. Vol
55. Lyon, France: World Health Organization, International Agency for
Research on Cancer, 1992. 139.
Valerie K, Delers A, Bruck C, et al. Activation of human immunodeficiency
virus type 1 by DNA damage in human cells. Nature 1988;333:78-81. 140.
Zmudzka BZ, Beer JZ. Activation
of human immunodeficiency virus by ultraviolet radiation (yearly review). Photochem
Photobiol 1990;52: 1153-62. 141.
Wallace BM, Lasker JS. Awakenings...UV light and HIV gene activation. Science
1992;257:1211-2. 142.
Valerie K, Rosenberg M. Chromatin structure implicated in activation of HIV-1
gene expression by ultraviolet light. New Biol 1990;2:712-8. 143.
Stein B, Rahmsdorf HJ, Steffen A, Litfin M, Herrlich P. UV-induced DNA damage
is an intermediate step in UV-induced expression of human immunodeficiency
virus type 1, collagenase, C-Fos, and metallathionein. Mol Cell Biol
1989;9:5169-81. 144.
Clerici M, Shearer GM. UV light exposure and HIV replication. Science
1992;258:1070-1. 145.
NIOSH. Hazard evaluation and technical assistance report: Onondaga County
Medical Examiner's Office, Syracuse, New York. Cincinnati: US Department of
Health and Human Services, Public Health Service, CDC, 1992; NIOSH report no.
HETA 92-171-2255. 146.
NIOSH. Hazard evaluation and technical assistance report: John C. Murphy
Family Health Center, Berkeley, Missouri. Cincinnati: US Department of Health
and Human Services, Public Health Service, CDC, 1992; NIOSH report no. HETA
91-148-2236. 147. NIOSH. Hazard evaluation and technical assistance report: San Francisco General Hospital and Medical Center, San Francisco, California. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1992; NIOSH report no. HETA 90-122-L2073. 148. Mature JM. Ultraviolet radiation and ventilation to help
control tuberculosis transmission: guidelines prepared for California Indoor
Air Quality Program. Berkeley, CA: Air and Industrial Hygiene Laboratory,
1989. 149.
Riley RL. Principles of UV air disinfection. Baltimore, MD: Johns Hopkins
University, School of Hygiene and Public Health, 1991. 150.
American Conference of Governmental Industrial Hygienists. Threshold limit
values and biological exposure indices for 1991-1992. Cincinnati: American
Conference of Governmental Industrial Hygienists, Inc., 1991. 151.
Bloom BR, Murray CJL. Tuberculosis: commentary on a reemergent killer. Science
1992;257:1055-64. 152.
Nardell EA. Dodging droplet nuclei: reducing the probability of nosocomial
tuberculosis transmission in the AIDS era. Am Rev Respir Dis 1990;142:501-3. 153.
US Department of Health and Human Services. 42 CFR Part 84: Respiratory
protective devices; proposed rule. Federal Register 1994;59:26849-89. 154.
American National Standards Institute. ANSI Z88.2-1980: American national
standard practices for respiratory protection. New York: American National
Standards Institute, 1980. 155.
Hyatt EC. Current problems and new developments in respiratory protection. Am
Ind Hyg Assoc J 1963;24:295-304. 156.
American National Standards Institute. ANSI Z88.2-1969: American national
standard practices for respiratory protection. New York: American National
Standards Institute, 1969. 157.
Lowry PL, Hesch PR, Revoir WH. Performance of single-use respirators. Am Ind
Hyg Assoc J 1977;38:462-7. 158.
Hyatt EC, et al. Respiratory studies for the National Institute for
Occupational Safety and Health -- July 1, 1972, through June 3, 1973. Los
Alamos, NM: Los Alamos Scientific Laboratory; progress report no. LA-5620-PR. 159.
Nelson KE, Larson PA, Schraufnagel DE, Jackson J. Transmission of
tuberculosis by fiber bronchoscopes. Am Rev Respir Dis 1983;127:97-100. 160.
Leers WD. Disinfecting endoscopes: how not to transmit Mycobacterium
tuberculosis by bronchoscopy. Can Med Assoc J 1980;123:275-83. 161.
Garner JS, Simmons BP. Guideline for isolation precautions in hospitals. Infect
Control 1983;4(suppl):245-325. 162.
Rutala WA. APIC guidelines for selection and use of disinfectants. Am J
Infect Control 1990;18:99-117. 163.
Favero MS, Bond WW. Chemical disinfection of medical and surgical materials. In:
Block SS, ed. Disinfection, sterilization, and preservation. 4th ed.
Philadelphia: Lea & Fabiger, 1991:617-41. 164.
Garner JS, Favero MS. Guideline for handwashing and hospital environmental
control. Atlanta: US Department of Health and Human Services, Public Health
Service, CDC, 1985. Glossary This
glossary contains many of the terms used in the guidelines, as well as others
that are encountered frequently by persons who implement TB infection-control
programs. The definitions given are not dictionary definitions but are those
most applicable to usage relating to TB. Acid-fast bacilli (AFB): Bacteria that retain certain dyes after being washed in an acid
solution. Most acid-fast organisms are mycobacteria. When AFB are seen on a
stained smear of sputum or other clinical specimen, a diagnosis of TB should
be suspected; however, the diagnosis of TB is not confirmed until a culture
is grown and identified as M. tuberculosis. Adherence:
Refers to the behavior of patients when they follow all aspects of the
treatment regimen as prescribed by the medical provider, and also refers to
the behavior of HCWs and employers when they follow all guidelines pertaining
to infection control. Aerosol:
The droplet nuclei that are expelled by an infectious person (e.g., by
coughing or sneezing); these droplet nuclei can remain suspended in the air
and can transmit M. tuberculosis to other persons. AIA: The
American Institute of Architects, a professional body that develops standards
for building ventilation. Air changes:
The ratio of the volume of air flowing through a space in a certain period of
time (i.e., the airflow rate) to the volume of that space (i.e., the room
volume); this ratio is usually expressed as the number of air changes per
hour (ACH). Air mixing:
The degree to which air supplied to a room mixes with the air already in the
room, usually expressed as a mixing factor. This factor varies from 1 (for
perfect mixing) to 10 (for poor mixing), and it is used as a multiplier to
determine the actual airflow required (i.e., the recommended ACH multiplied
by the mixing factor equals the actual ACH required). Alveoli:
The small air sacs in the lungs that lie at the end of the bronchial tree;
the site where carbon dioxide in the blood is replaced by oxygen from the
lungs and where TB infection usually begins. Anergy:
The inability of a person to react to skin-test antigens (even if the person
is infected with the organisms tested) because of immunosuppression. Anteroom:
A small room leading from a corridor into an isolation room; this room can
act as an airlock, preventing the escape of contaminants from the isolation
room into the corridor. Area: A
structural unit (e.g., a hospital ward or laboratory) or functional unit (e.g.,
an internal medicine service) in which HCWs provide services to and share air
with a specific patient population or work with clinical specimens that may
contain viable M. tuberculosis organisms. The risk for exposure to M.
tuberculosis in a given area depends on the prevalence of TB in the
population served and the characteristics of the environment. ASHRAE:
The American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc., a professional body that develops standards for building ventilation. Asymptomatic: Without symptoms, or producing no symptoms. Bacillus of Calmette and Guerin (BCG) vaccine: A TB vaccine used in many parts
of the world. BACTEC(R):
One of the most often used radiometric methods for detecting the early growth
of mycobacteria in culture. It provides rapid growth (in 7-14 days) and rapid
drug-susceptibility testing (in 5-6 days). When BACTEC(R) is used with rapid
species identification methods, M. tuberculosis can be identified within
10-14 days of specimen collection. Booster phenomenon: A phenomenon in which some persons (especially older adults) who are
skin tested many years after infection with M. tuberculosis have a negative
reaction to an initial skin test, followed by a positive reaction to a
subsequent skin test. The second (i.e., positive) reaction is caused by a
boosted immune response. Two-step testing is used to distinguish new
infections from boosted reactions (see Two-step testing). Bronchoscopy: A procedure for examining the respiratory tract that requires
inserting an instrument (a bronchoscope) through the mouth or nose and into
the trachea. The procedure can be used to obtain diagnostic specimens. Capreomycin:
An injectable, second-line anti-TB drug used primarily for the treatment of
drug-resistant TB. Cavity: A
hole in the lung resulting from the destruction of pulmonary tissue by TB or
other pulmonary infections or conditions. TB patients who have cavities in
their lungs are referred to as having cavitary disease, and they are often
more infectious than TB patients without cavitary disease. Chemotherapy: Treatment of an infection or disease by means of oral or injectable
drugs. Cluster:
Two or more PPD skin-test conversions occurring within a 3-month period among
HCWs in a specific area or occupational group, and epidemiologic evidence
suggests occupational (nosocomial) transmission. Contact: A
person who has shared the same air with a person who has infectious TB for a
sufficient amount of time to allow possible transmission of M. tubercuosis. Conversion, PPD: See PPD test conversion. Culture:
The process of growing bacteria in the laboratory so that organisms can be
identified. Cycloserine:
A second-line, oral anti-TB drug used primarily for treating drug-resistant
TB. Directly observed therapy (DOT): An adherence-enhancing strategy in which an
HCW or other designated person watches the patient swallow each dose of
medication. DNA probe:
A technique that allows rapid and precise identification of mycobacteria
(e.g., M. tuberculosis and M. bovis) that are grown in culture. The
identification can often be completed in 2 hours. Droplet nuclei: Microscopic particles (i.e., 1-5 um in diameter) produced when a
person coughs, sneezes, shouts, or sings. The droplets produced by an
infectious TB patient can carry tubercle bacilli and can remain suspended in
the air for prolonged periods of time and be carried on normal air currents
in the room. Drug resistance, acquired: A resistance to one or more anti-TB drugs
that develops while a patient is receiving therapy and which usually results
from the patient's nonadherence to therapy or the prescription of an
inadequate regimen by a health-care provider. Drug resistance, primary: A resistance to one or more anti-TB drugs that exists before a
patient is treated with the drug(s). Primary resistance occurs in persons
exposed to and infected with a drug-resistant strain of M. tuberculosis. Drug-susceptibility pattern: The anti-TB drugs to which the tubercle bacilli
cultured from a TB patient are susceptible or resistant based on
drug-susceptibility tests. Drug-susceptibility tests: Laboratory tests that determine whether the
tubercle bacilli cultured from a patient are susceptible or resistant to
various anti-TB drugs. Ethambutol:
A first-line, oral anti-TB drug sometimes used concomitantly with INH,
rifampin, and pyrazinamide. Ethionamide:
A second-line, oral anti-TB drug used primarily for treating drug-resistant
TB. Exposure:
The condition of being subjected to something (e.g., infectious agents) that
could have a harmful effect. A person exposed to M. tuberculosis does not
necessarily become infected (see Transmission). First-line drugs: The most often used anti-TB drugs (i.e., INH, rifampin, pyrazinamide,
ethambutol, and streptomycin). Fixed room-air HEPA recirculation systems: Nonmobile devices or systems that remove
airborne contaminants by recirculating air through a HEPA filter. These may
be built into the room and permanently ducted or may be mounted to the wall
or ceiling within the room. In either situation, they are fixed in place and
are not easily movable. Fluorochrome stain: A technique for staining a clinical specimen with fluorescent dyes to
perform a microscopic examination (smear) for mycobacteria. This technique is
preferable to other staining techniques because the mycobacteria can be seen
easily and the slides can be read quickly. Fomites:
Linens, books, dishes, or other objects used or touched by a patient. These
objects are not involved in the transmission of M. tuberculosis. Gastric aspirate: A procedure sometimes used to obtain a specimen for culture when a
patient cannot cough up adequate sputum. A tube is inserted through the mouth
or nose and into the stomach to recover sputum that was coughed into the
throat and then swallowed. This procedure is particularly useful for
diagnosis in children, who are often unable to cough up sputum. High-efficiency particulate air (HEPA) filter: A specialized filter that is
capable of removing 99.97% of particles greater than or equal to 0.3 um in
diameter and that may assist in controlling the transmission of M.
tuberculosis. Filters may be used in ventilation systems to remove particles
from the air or in personal respirators to filter air before it is inhaled by
the person wearing the respirator. The use of HEPA filters in ventilation
systems requires expertise in installation and maintenance. Human immunodeficiency virus (HIV) infection: Infection with the virus that
causes acquired immunodeficiency syndrome (AIDS). HIV infection is the most
important risk factor for the progression of latent TB infection to active
TB. Immunosuppressed: A condition in which the immune system is not functioning normally
(e.g., severe cellular immunosuppression resulting from HIV infection or
immunosuppressive therapy). Immunosuppressed persons are at greatly increased
risk for developing active TB after they have been infected with M.
tuberculosis. No data are available regarding whether these persons are also
at increased risk for infection with M. tuberculosis after they have been
exposed to the organism. Induration:
An area of swelling produced by an immune response to an antigen. In
tuberculin skin testing or anergy testing, the diameter of the indurated area
is measured 48-72 hours after the injection, and the result is recorded in
millimeters. Infection:
The condition in which organisms capable of causing disease (e.g., M.
tuberculosis) enter the body and elicit a response from the host' s immune
defenses. TB infection may or may not lead to clinical disease. Infectious:
Capable of transmitting infection. When persons who have clinically active
pulmonary or laryngeal TB disease cough or sneeze, they can expel droplets
containing M. tuberculosis into the air. Persons whose sputum smears are
positive for AFB are probably infectious. Injectable:
A medication that is usually administered by injection into the muscle
(intramuscular [IM]) or the bloodstream (intravenous [IV]). Intermittent therapy: Therapy administered either two or three times per week, rather than
daily. Intermittent therapy should be administered only under the direct
supervision of an HCW or other designated person (see Directly observed
therapy [DOT]). Intradermal:
Within the layers of the skin. Isoniazid (INH): A first-line, oral drug used either alone as preventive therapy or in
combination with several other drugs to treat TB disease. Kanamycin:
An injectable, second-line anti-TB drug used primarily for treatment of
drug-resistant TB. Latent TB infection: Infection with M. tuberculosis, usually detected by a positive PPD
skin-test result, in a person who has no symptoms of active TB and who is not
infectious. Mantoux test: A method of skin testing that is performed by injecting 0.1 mL of
PPD-tuberculin containing 5 tuberculin units into the dermis (i.e., the
second layer of skin) of the forearm with a needle and syringe. This test is
the most reliable and standardized technique for tuberculin testing (see
Tuberculin skin test and Purified protein derivative [PPD]-tuberculin test). Multidrug-resistant tuberculosis (MDR-TB): Active TB caused by M. tuberculosis
organisms that are resistant to more than one anti-TB drug; in practice,
often refers to organisms that are resistant to both INH and rifampin with or
without resistance to other drugs (see Drug resistance, acquired and Drug
resistance, primary). M. tuberculosis complex: A group of closely related mycobacterial species that can cause
active TB (e.g., M. tuberculosis, M. bovis, and M. africanum); most TB in the
United States is caused by M. tuberculosis. Negative pressure: The relative air pressure difference between two areas in a
health-care facility. A room that is at negative pressure has a lower
pressure than adjacent areas, which keeps air from flowing out of the room
and into adjacent rooms or areas. Nosocomial:
An occurrence, usually an infection, that is acquired in a hospital or as a
result of medical care. Para-aminosalicylic acid: A second-line, oral anti-TB drug used for treating drug-resistant TB. Pathogenesis: The pathologic, physiologic, or biochemical process by which a
disease develops. Pathogenicity: The quality of producing or the ability to produce pathologic changes
or disease. Some nontuberculous mycobacteria are pathogenic (e.g.,
Mycobacterium kansasii), and others are not (e.g., Mycobacterium phlei). Portable room-air HEPA recirculation units: Free-standing portable devices
that remove airborne contaminants by recirculating air through a HEPA filter. Positive PPD reaction: A reaction to the purified protein derivative (PPD)-tuberculin skin
test that suggests the person tested is infected with M. tuberculosis. The
person interpreting the skin-test reaction determines whether it is positive
on the basis of the size of the induration and the medical history and risk
factors of the person being tested. Preventive therapy: Treatment of latent TB infection used to prevent the progression of
latent infection to clinically active disease. Purified protein derivative (PPD)-tuberculin: A purified tuberculin preparation
that was developed in the 1930s and that was derived from old tuberculin. The
standard Mantoux test uses 0.1 mL of PPD standardized to 5 tuberculin units. Purified protein derivative (PPD)-tuberculin test: A method used to evaluate the
likelihood that a person is infected with M. tuberculosis. A small dose of
tuberculin (PPD) is injected just beneath the surface of the skin, and the
area is examined 48-72 hours after the injection. A reaction is measured
according to the size of the induration. The classification of a reaction as
positive or negative depends on the patient's medical history and various
risk factors (see Mantoux test). Purified protein derivative (PPD)-tuberculin test conversion: A change in PPD test results from
negative to positive. A conversion within a 2-year period is usually
interpreted as new M. tuberculosis infection, which carries an increased risk
for progression to active disease. A booster reaction may be misinterpreted
as a new infection (see Booster phenomenon and Two-step testing). Pyrazinamide: A first-line, oral anti-TB drug used in treatment regimens. Radiography:
A method of viewing the respiratory system by using radiation to transmit an
image of the respiratory system to film. A chest radiograph is taken to view
the respiratory system of a person who is being evaluated for pulmonary TB. Abnormalities
(e.g., lesions or cavities in the lungs and enlarged lymph nodes) may
indicate the presence of TB. Radiometric method: A method for culturing a specimen that allows for rapid detection of
bacterial growth by measuring production of CO(2) by viable organisms; also a
method of rapidly performing susceptibility testing of M. tuberculosis. Recirculation: Ventilation in which all or most of the air that is exhausted from an
area is returned to the same area or other areas of the facility. Regimen:
Any particular TB treatment plan that specifies which drugs are used, in what
doses, according to what schedule, and for how long. Registry:
A record-keeping method for collecting clinical, laboratory, and radiographic
data concerning TB patients so that the data can be organized and made
available for epidemiologic study. Resistance:
The ability of some strains of bacteria, including M. tuberculosis, to grow
and multiply in the presence of certain drugs that ordinarily kill them; such
strains are referred to as drug-resistant strains. Rifampin:
A first-line, oral anti-TB drug that, when used concomitantly with INH and
pyrazinamide, provides the basis for short-course therapy. Room-air HEPA recirculation systems and units: Devices (either fixed or
portable) that remove airborne contaminants by recirculating air through a
HEPA filter. Second-line drugs: Anti-TB drugs used when the first-line drugs cannot be used (e.g.,
for drug-resistant TB or because of adverse reactions to the first-line
drugs). Examples are cycloserine, ethionamide, and capreomycin. Single-pass ventilation: Ventilation in which 100% of the air supplied to an area is exhausted
to the outside. Smear (AFB smear): A laboratory technique for visualizing mycobacteria. The specimen is
smeared onto a slide and stained, then examined using a microscope. Smear
results should be available within 24 hours. In TB, a large number of
myco-bacteria seen on an AFB smear usually indicates infectiousness. However,
a positive result is not diagnostic of TB because organisms other than M.
tuberculosis may be seen on an AFB smear (e.g., nontuberculous mycobacteria). Source case:
A case of TB in an infectious person who has transmitted M. tuberculosis to
another person or persons. Source control: Controlling a contaminant at the source of its generation, which
prevents the spread of the contaminant to the general work space. Specimen:
Any body fluid, secretion, or tissue sent to a laboratory where smears and
cultures for M. tuberculosis will be performed (e.g., sputum, urine, spinal
fluid, and material obtained at biopsy). Sputum:
Phlegm coughed up from deep within the lungs. If a patient has pulmonary
disease, an examination of the sputum by smear and culture can be helpful in
evaluating the organism responsible for the infection. Sputum should not be
confused with saliva or nasal secretions. Sputum induction: A method used to obtain sputum from a patient who is unable to cough
up a specimen spontaneously. The patient inhales a saline mist, which
stimulates a cough from deep within the lungs. Sputum smear, positive: AFB are visible on the sputum smear when viewed under a microscope. Persons
with a sputum smear positive for AFB are considered more infectious than
those with smear-negative sputum. Streptomycin: A first-line, injectable anti-TB drug. Symptomatic:
Having symptoms that may indicate the presence of TB or another disease (see
Asymptomatic). TB case: A
particular episode of clinically active TB. This term should be used only to
refer to the disease itself, not the patient with the disease. By law, cases
of TB must be reported to the local health department. TB infection: A condition in which living tubercle bacilli are present in the body
but the disease is not clinically active. Infected persons usually have
positive tuberculin reactions, but they have no symptoms related to the
infection and are not infectious. However, infected persons remain at
lifelong risk for developing disease unless preventive therapy is given. Transmission: The spread of an infectious agent from one person to another. The likelihood
of transmission is directly related to the duration and intensity of exposure
to M. tuberculosis (see Exposure). Treatment failures: TB disease in patients who do not respond to chemotherapy and in
patients whose disease worsens after having improved initially. Tubercle bacilli: M. tuberculosis organisms. Tuberculin skin test: A method used to evaluate the likelihood that a person is infected
with M. tuberculosis. A small dose of PPD-tuberculin is injected just beneath
the surface of the skin, and the area is examined 48-72 hours after the
injection. A reaction is measured according to the size of the induration. The
classification of a reaction as positive or negative depends on the patient's
medical history and various risk factors (see Mantoux test, PPD test). Tuberculosis (TB): A clinically active, symptomatic disease caused by an organism in the
M. tuberculosis complex (usually M. tuberculosis or, rarely, M. bovis or M.
africanum). Two-step testing: A procedure used for the baseline testing of persons who will
periodically receive tuberculin skin tests (e.g., HCWs) to reduce the
likelihood of mistaking a boosted reaction for a new infection. If the
initial tuberculin-test result is classified as negative, a second test is
repeated 1-3 weeks later. If the reaction to the second test is positive, it
probably represents a boosted reaction. If the second test result is also
negative, the person is classified as not infected. A positive reaction to a
subsequent test would indicate new infection (i.e., a skin-test conversion)
in such a person. Ultraviolet germicidal irradiation (UVGI): The use of ultraviolet radiation to kill or
inactivate microorganisms. Ultraviolet germicidal irradiation (UVGI) lamps: Lamps that kill or inactivate
microorganisms by emitting ultraviolet germicidal radiation, predominantly at
a wavelength of 254 nm (intermediate light waves between visible light and
X-rays). UVGI lamps can be used in ceiling or wall fixtures or within air
ducts of ventilation systems. Ventilation, dilution: An engineering control technique to dilute and remove airborne
contaminants by the flow of air into and out of an area. Air that contains
droplet nuclei is removed and replaced by contaminant-free air. If the flow
is sufficient, droplet nuclei become dispersed, and their concentration in
the air is diminished. Ventilation, local exhaust: Ventilation used to capture and remove
airborne contaminants by enclosing the contaminant source (i.e., the patient)
or by placing an exhaust hood close to the contaminant source. Virulence:
The degree of pathogenicity of a microorganism as indicated by the severity
of the disease produced and its ability to invade the tissues of a host. M.
tuberculosis is a virulent organism. Appendix B Smoke-Trail Testing Method for Negative pressure
Isolation Room Test
Method Description: One
of the purposes of a negative pressure TB isolation room is to prevent TB
droplet nuclei from escaping the isolation room and entering the corridor or
other surrounding uncontaminated spaces. To check for negative room pressure,
use smoke-trails to demonstrate that the pressure differential is inducing
airflow from the corridor, through the crack at the bottom of the door
(undercut) and into the isolation room. When performing a smoke-trail test
follow these recommendations where applicable: 1.
Test only with the isolation room door shut. If not equipped with an
anteroom, it is assumed that there will be a loss of space pressure control
when the isolation door is opened and closed. It is not necessary to
demonstrate direction of airflow when the door is open. 2.
If there is an anteroom, release smoke at the inner door undercut, with both
anteroom doors shut. 3.
In addition to a pedestrian entry, some isolation rooms are also accessed
through a wider wheeled-bed stretcher door. Release smoke at all door
entrances to isolation rooms. 4.
So that the smoke is not blown into the isolation room, hold the smoke
bottle/tube parallel to the door so the smoke is released perpendicular to
the direction of airflow through the door undercut. 5.
Position the smoke bottle/tube tight to the floor, centered in the middle of
the door jamb and approximately two inches out in front of the door. 6.
Release a puff of smoke and observe the resulting direction of airflow. Repeat
the test at least once or until consistent results are obtained. 7.
Minimize momentum imparted to the smoke by squeezing the bulb or bottle
slowly. This will also help minimize the volume of smoke released. 8.
Depending on the velocity of the air through the door undercut, the smoke
plume will either stay disorganized or it will form a distinct streamline. In
either case, the smoke will directionally behave in one of three ways. It
will: a. go through the door undercut into the
isolation room, b. remain motionless, or c. be blown back into the corridor. Compliance
with the intent of the CDC Guidelines for negative pressure requires that the
smoke be drawn into the isolation room through the door undercut. 9.
Release smoke from the corridor side of the door only for occupied TB
isolation rooms. If the room is unoccupied, also release smoke inside the
isolation room (same position as in Step No. 5) to verify that released smoke
remains contained in the isolation room (i.e., smoke as a surrogate for TB
droplet nuclei). 10.
If photography is performed or videotaping, it is recommended that a dark
surface be placed on the floor to maximize contrast. Be aware that most
autofocusing cameras cannot focus on smoke. Testing
"As Used" Conditions: Testing
of negative pressure isolation rooms requires that the test reflect
"as-used" conditions. Consider the following use variables which
may affect space pressurization and the performance of the negative pressure
isolation room: 1.
Patient toilet rooms are mechanically exhausted to control odors. The
position of the toilet room door may affect the pressure differential between
the isolation room and the corridor. Smoke-trail tests should be performed
with the toilet room door open and the toilet room door closed. This will not
be necessary if the toilet room door is normally closed and controlled to
that position by a mechanical door closer. 2.
An open window will adversely affect the performance of a negative pressure
isolation room. If the isolation room is equipped with an operable window,
perform smoke-trail tests with the window open and the window closed. 3.
There may be corridor doors that isolate the respiratory ward or wing from
the rest of the facility. These corridor doors are provided in the initial
design to facilitate space pressurization schemes and/or building life safety
codes. Direct communication with the rest of the facility may cause pressure
transients in the corridor (e.g., proximity to an elevator lobby) and affect
the performance of the isolation room. Perform isolation room smoke-trail
testing with these corridor doors in their "as-used" position which
is either normally open or normally closed. 4.
Isolation rooms may be equipped with auxiliary, fan-powered, recirculating,
stand alone HEPA filtration or UV units. These units must be running when
smoke-trail tests are performed. 5.
Do not restrict corridor foot traffic while performing smoke-trail tests. 6.
Negative pressure is accomplished by exhausting more air than is supplied to
the isolation room. Some HVAC systems employ variable air volume (VAV) supply
air and sometimes VAV exhaust air. By varying the supply air delivered to the
space to satisfy thermal requirements, these VAV systems can adversely impact
the performance of a negative pressure isolation room. If the isolation room
or the corridor is served by a VAV system you should perform the smoke test
twice. Perform the smoke test with the zone thermostat thermally satisfied
and again with the zone thermostat thermally unsatisfied thus stimulating the
full volumetric flowrate range of the VAV system serving the area being
tested. Smoke: Most
smoke tubes, bottles and sticks use titanium chloride (TiCl(4)) to produce a
visible fume. There is no OSHA PEL or ACGIH TLV for this chemical although it
is a recognized inhalation irritant. Health care professionals are concerned
about releasing TiCl(4) around pulmonary patients. The smoke released at the
door undercut makes only one pass through the isolation room and is exhausted
directly outside. Isolation room air is typically not
"recirculated." The
CDC in the supplementary information to the 1994 TB Guidelines has indicated
that "The concern over the use of smoke is unfounded." Controlled
tests by NIOSH have shown that the quantity of smoke that is released is so
minute that it is not measurable in the air. Nonirritating smoke tubes are
available and should never-the-less be utilized whenever possible. |
|