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TB Notes 1, 2000
Introduction
Where We've Been and Where We're Going: Perspectives from CDC's Partners in TB Control
Changes I've Seen
TB Control in New York City: A Recent History
Not by DOT Alone
Baltimore at the New Millennium
From Crickets to Condoms and Beyond
The Denver TB Program: Opportunity, Creativity, Persistence, and Luck
National Jewish: The 100-Year War Against TB
Earthquakes, Population Growth, and TB in Los Angeles County
TB in Alaska
CDC and the American Lung Association/ American Thoracic Society: an Enduring Public/Private Partnership
The Unusual Suspects
The Model TB Prevention and Control Centers: History and Purpose
My Perspective on TB Control over the Past Two to Three Decades
History of the IUATLD
Thoughts about the Future of TB Control in the United States
Where We've Been and Where We're Going: Perspectives from CDC
Early History of the CDC TB Division, 1944-1985
CDC Funding for TB Prevention and Control
Managed Care and TB Control - A New Era
Early Research Activities of the TB Control Division
The First TB Drug Clinical Trials
Current TB Drug Trials: The Tuberculosis Trials Consortium (TBTC)
TB Communications and Education
TB Control in the Information Age
Field Services Activities
TB's Public Health Heroes
Infection Control Issues
A Decade of Notable TB Outbreaks: A Selected Review
International Activities
The Role of CDC's Division of Quarantine in the Fight Against TB in the U.S.
The STOP TB Initiative, A Global Partnership
Seize the Moment - Personal Reflections
 
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TB Notes 1, 2000

Infection Control Issues

by Renee Ridzon, MD
Surveillance and Epidemiology Branch

In recent years, transmission of TB within the workplace has received much attention in the scientific and popular press. However, the notion of TB as an occupational hazard is not new, and since the beginning of this century TB has been recognized as an occupational hazard for doctors and nurses. In fact, there have been several studies published in the first part of the 1900s documenting low rates of M. tuberculosis infection among medical and nursing students prior to the start of training. After completion of clerkships caring for TB patients, high rates of tuberculin skin test conversions and even cases of TB were seen. Concern about this occupational risk waned, however, with the dramatic fall in the number of TB cases in the US.

With the re-emergence of TB in the mid-1980s, the emergence of multidrug-resistant TB (MDR TB), and recognition of the increased morbidity caused by MDR TB and HIV-related TB, concern regarding TB was reawakened in this country. Media reports about the danger of TB were fueled by a number of published reports regarding explosive outbreaks of MDR TB in hospitals, mostly in New York City, among persons with HIV infection. Concern was further heightened by episodes of transmission of disease to health care workers caring for the patients involved in these outbreaks.

With recognition of the increased risk for TB among persons with HIV infection, in 1990 CDC issued Guidelines for Preventing the Transmission of Tuberculosis in Health-Care Settings with Special Focus on HIV-Related Issues. Despite these guidelines, implementation of appropriate infection control measures was incomplete in many hospitals, and some of the published reports of nosocomial transmission documented lapses in or absence of infection control measures in the health care facilities. Because of its legal mandate to ensure that no worker is harmed as a result of his or her work experience, as well as the outbreaks of MDR TB, in 1992 the National Institute for Occupational Safety and Health (NIOSH) recommended the use of powered-air purifying respirators (PAPRs) by health care workers potentially exposed to M. tuberculosis.

As a result of the ongoing outbreaks of TB and the NIOSH recommendation for the use of PAPRs, the adequacy of the 1990 guidelines was discussed at a large national meeting convened in 1993. In attendance at this meeting were representatives from multiple groups concerned with nosocomial transmission of M. tuberculosis, including infection control practitioners, labor representatives, and occupational medicine practitioners. The meeting concluded that in most of the outbreak settings, the 1990 guidelines had not been adequately implemented, and there was a need for revised and expanded guidelines. In 1993 a draft of the revised guidelines was published in the Federal Register for public comment. After a period of comment and public meetings, the report Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities, 1994 was published in the Morbidity and Mortality Weekly Report. This document contained detailed, comprehensive recommendations for prevention of nosocomial transmission of M. tuberculosis. Included in the recommendations was a hierarchy of controls composed of, most importantly, administrative controls (including assignment of responsibility, risk assessment, development of a TB infection control plan with periodic reassessment, and tuberculin skin testing of health care workers), followed by engineering controls, and then by personal respiratory protection. Personal respiratory protection devices that were recommended for use in the health care setting needed to meet the following criteria:

  1. ability to filter particles of 1 micron with a filter efficiency of 95%,
  2. ability to be fit tested to obtain a face seal leak of 10% or less,
  3. ability to fit different face sizes, and
  4. ability to be checked for face-piece fit by health care workers each time the respirator was used.
At the time the 1994 guidelines were written, the only respiratory protection device that was NIOSH-approved and met the above criteria was the high efficiency particulate air (HEPA) filter respirators. In July 1995 NIOSH updated its respirator testing and certification requirements to permit the approval of other respirators. Under the updated testing, respirators that contain a NIOSH-certified N-series filter with 95% efficiency (N-95) rating meet the recommendations of the CDC guidelines.

Image 1: Hierarchy of TB infection control measures

Like NIOSH, the Occupational Safety and Health Administration (OSHA) has a legal mandate for the protection of workers; however, unlike NIOSH, which can only issue recommendations, OSHA has the capacity to enforce its standards. In 1997, OSHA published a draft TB standard in the Federal Register. Following the publication of the draft standard, there was a period for public comment followed by a series of hearings for testimony. Detailed comments were submitted from a CDC committee including staff members of NIOSH, the Hospital Infections Program, and the Division of Tuberculosis Elimination, as well as many other professional organizations. In July 1999, OSHA reopened the docket for further public comment. The OSHA TB standard is currently undergoing revision, and its final content and release date are not yet known.

Image 2: Graphic of an example of personal respiratory protection device for health care workers.

In order to better understand the risk of transmission of M. tuberculosis to health care workers, CDC undertook several studies designed to examine rates of skin test conversions in health care workers. The most comprehensive of these was a study initiated in 1995 called StaffTRAK-TB. This study included over 13,000 health care workers. Data from this study demonstrate a rate of skin test conversions among health care workers of 4.4 conversions per 1,000 person-years of follow-up. For US-born persons, the rate was even lower at 3.2 conversions per 1,000 person-years. From data currently available from studies such as StaffTRAK-TB, the risk of nosocomial transmission of TB appears to be quite low. As a result CDC is considering revision of the 1994 guidelines, especially in the areas of frequency of tuberculin skin testing of health care workers.

The risk of transmission of M. tuberculosis in health care settings is a real one. However, the magnitude of this risk depends on many factors such as implementation of administrative and engineering controls, prevalence of patients with infectious TB within the facility, and risk for infection outside of the healthcare facility. All of these factors need to be weighed in decisions regarding recommendations or mandates for TB control measures within health care facilities. As the rates of TB in the US continue to decline, these recommendations will need to be tailored to offer protection to patients and workers within the health care setting, without an unnecessary burden of testing and expense.

 


Released October 2008
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