Nosocomial epidemic of active tuberculosis among HIV-infected patients

In an investigation of a nosocomial outbreak of tuberculosis, 18 HIV-infected inpatients were found to have been exposed to Mycobacterium tuberculosis; active tuberculosis developed in 8, 7 within 60 days of diagnosis of the index case. The patients with lower total lymphocyte and CD4 lymphocyte counts were more likely to get the disease than were those with higher counts. A low score on multiple antigen skin testing was also associated with the development of active tuberculosis. 4 of the 18 patients had a positive tuberculin skin test before exposure to M tuberculosis; none of them subsequently got the disease.