Analysis of Mycobacterium tuberculosis transmission patterns in a homelessshelter outbreak

SETTING: From July 1997 through May 1998, ten tuberculosis (TB) cases were reported among men in a Syracuse New York homeless shelter for men. OBJECTIVE AND DESIGN: Investigation to determine extent of, and prevent fur ther, transmission of Mycobacterium tuberculosis. RESULTS: Epidemiologic and laboratory evidence suggests that eight of the t en cases were related. Seven cases had isolates with matching six-band IS61 10 DNA fingerprints; the isolate from another case had a closely related fi ngerprint pattern and this case was considered to be caused by a variant of the same strain. Isolates from eight cases had identical spoligotypes. The source case had extensive cavitary disease and stayed at the shelter night ly, while symptomatic, for almost 8 months before diagnosis. A contact inve stigation was conducted among 257 shelter users and staff, 70% of whom had a positive tuberculin skin test, including 21 with documented skin test con versions. CONCLUSIONS: An outbreak of related TB cases in a high-risk setting was con firmed through the use of IS6110 DNA fingerprinting in conjunction with spo ligotyping and epidemiologic evidence. Because of the high rate of infectio n in the homeless population, routine screening for TB and preventive thera py for eligible persons should be considered in shelters.