Data relating to ambulatory facilities and their employees are sparse. An outbreak of tuberculous infection occurred among health care workers in a Palm Beach County, Florida, clinic in 1988 (70). Of 30 previously skin test-negative employees, 17 became tuberculin-positive. The clinic ventilation system provided greater than 90 percent recirculation of air with less than one-half fresh air changes per hour. In a nonoutbreak setting, 766 tuberculin-negative health care workers in 16 urban ambulatory care units caring for HIV-infected patients, six of which were located in greater New York City, participated in a prospective tuberculin skin testing study in 1992 and 1993 (71). The conversion rate in these individuals was 1.6 per 100 person-years.
Prezant and colleagues studied prospectively a cohort of New York City prehospital health care workers consisting of nearly 200 emergency medical technicians and paramedics who had been stably employed in their positions for at least 15 years (72). Documented tuberculin skin test conversions occurred in one worker in 1993, none in 1994, one in 1995, and three in 1996. Overall, the calculated annual risk of infection for this small group was 0.6 percent/year.
A single report described a survey of 56 American clinical microbiology laboratories processing samples for culture of mycobacteria (73). Fourteen tuberculin skin test conversions were noted, but neither the time interval nor the number of persons at risk were given, so that no conclusions can be drawn from this report.
Transmission of tuberculous infection from cadavers is well known, and autopsy rooms have been considered especially hazardous. Much of the past tuberculous infection risk for medical students cited previously was attributed to participation in autopsies. In a county medical examiner’s office in New York State 2 of 15 morgue assistants converted their tuberculin skin tests during a 15-month period (calculated ARI = 10.8 percent/ year) (74). This facility performed autopsies on deceased inmates from a nearby prison, and eight autopsies had been performed on tuberculous individuals during that time. In a further autopsy risk, prosector’s wart occurs as a result of direct percutaneous inoculation of M. tuberculosis; there are no data on its frequency.
Recently transmission of M. tuberculosis has been documented and much publicized in funeral homes. Gershon and coworkers surveyed 864 funeral home workers who were attending a convention of the National Funeral Directors Association (75). Of them, 101 (11.7 percent) were tuberculin skin test positive. Reactivity correlated positively with older age, male gender, and nonwhite race. After controlling for these factors, reactivity was twice as frequent among embalmers as other funeral home employees.
Sterling and colleagues reported the first episode of documented transmission of tuberculous infection from a cadaver to an embalmer (76).