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Rh of MDR-TB in institutional settings. From 1990 through early 1992, in collaboration with state and local health departments, CDC investigated numerous outbreaks of MDR-TB in hospitals and correctional facilities in Florida and New York (7,8,9). To date, these outbreaks have included over 200 tuberculosis cases. Virtually all of these cases have had organisms resistant to both INH and rifampin, and some have had organisms resistant to up to seven antituberculosis drugs. Most of the patients in these outbreaks were infected with HIV. Mortality among patients with MDR-TB in these outbreaks has been very high, ranging from 72 to 89%, and the median interval between diagnosis and death has been very short, from 4 to 16 weeks.

In addition to hospitalized patients and inmates, occupational transmission of MDR-TB to health-care-facility workers and prison guards has been documented. At least nine of these workers have developed clinically active MDR-TB, and five of them have died. Of the eight health-care-facility workers who developed clinically active MDR-TB, five were known to be infected with HIV (8).

The continuing occupational hazard of tuberculosis infection in health-care-facilities in conjunction with the continuing outbreaks of tuberculosis in health-care-facility workers led NIOSH to reexamine the role of personal respiratory protection in preventing occupational transmission of tuberculosis infection in health-care settings. There is a paucity of data from well-designed studies regarding both the efficacy and reliability of precautions such as administrative controls, ventilation systems, and particulate respirators (PRs) that are currently recommended (10). Regarding the efficacy of ventilation and respirators currently recommended, the following report was given in a summary of a January 1992 conference (11):