NOSOCOMIAL TRANSMISSION OF MYCOBACTERIUM-TUBERCULOSIS - ROLE OF HEALTH-CARE WORKERS IN OUTBREAK PROPAGATION

To investigate an outbreak of tuberculosis (TB) among health care work ers (HCWs) at a county hospital, all patients with culture-confirmed T B on wards A and B and all HCWs working at least one shift on these wa rds from January 1991 through March 1992 were studied. Tuberculin skin test conversions occurred in 30% (ward A) and 48% (ward B) of HCWs; 8 developed active TB. Workers exposed for at least one shift to worker s or patients with active TB were more likely to have skin test conver sion than were workers who were not exposed (ward A exposure relative risk [RR] for workers = 2.8, P = .005, and for patients = 2.2, P > .5; ward B exposure RR for workers = 2.8, P < .001, and for patients = 5. 3, P < .001). Underlying conditions and performing charting activities in the nurses' work room were associated with progression to active T B among infected workers. Transmission was facilitated by delays of le ss than or equal to 2.5 months in treatment of workers with skin test conversion or TB symptoms.