Increased Incidence of the Outbreak Strain of Mycobacterium tuberculosis in the Surrounding Community after an Outbreak in a Jail

BACKGROUND: Between 1995 and 1997, a tuberculosis outbreak occurred in a large, urban jail. We investigated whether the outbreak strain of Mycobacterium tuberculosis (M. tuberculosis) was circulating in the surrounding community after that outbreak. METHODS: We performed a retrospective cohort study of people with tuberculosis in Shelby County, TN, from January 1998 through August 1999, with molecular fingerprinting of M. tuberculosis strains. RESULTS: From January 1998 through August 1999, 23% of cases in the community involved a strain of M. tuberculosis that was indistinguishable from the previous jail outbreak strain. Twelve people (63%) with that strain had no history of recent incarceration. CONCLUSION: Two years after a tuberculosis outbreak in the jail, the outbreak strain was more prevalent in the surrounding community than it was during the jail outbreak. Jails can be important reservoirs of tuberculosis, which may subsequently circulate outside the institution. If efforts to eliminate tuberculosis are to be successful, the disease must be controlled successfully in such high-risk populations.