Nosocomial outbreak of tuberculosis in an outpatient HIV treatment room

Objective: To investigate a possible outbreak of tuberculosis in an outpatient HIV treatment facility in Sydney, Australia. Design: Following the diagnosis of pulmonary tuberculosis in an attendee, a prospective screening program was instituted to investigate the potential outbreak. Methods: Screening of 89 potentially exposed patients included chest radiographs (n = 89), and sputum examination (n = 37) over a period of 23 weeks. Results: No cases of tuberculosis were detected by the screening program. However, three (3.4%) of this cohort developed pulmonary tuberculosis between 8 and 10 weeks following the diagnosis of the index case. The incidence of active tuberculosis during the follow-up period (median, 7.4 months) was 5.3 per 100 person years and represents the lower limit of possible tuberculous infection, as both latent infection, and undiagnosed tuberculosis among those who died could not be excluded. Mycobacterium tuberculosis strains isolated from the index case and three subsequent cases were found to be identical by DNA typing. Conclusion: Nosocomial transmission of tuberculosis in an outpatient treatment setting has been demonstrated. The risk of nosocomial transmission of tuberculosis is significant in institutions caring for HIV-infected patients even in countries with a low prevalence of tuberculosis infection, and highlights the importance of adherence to tuberculosis control guidlines.