The role of core groups in transmitting Mycobacterium tuberculosis in a high prevalence community in Southern Mexico

SETTING: A community in Southern Mexico with a high prevalence of tuberculo sis. OBJECTIVE: To characterize the transmission dynamics in a region with a DOT S-based tuberculosis control program. DESIGN: Community-based screening of chronic coughers between 1 March 1995 and 31 August 1996, Individuals with acid-fast bacilli (AFB) in their sputu m were enrolled, interviewed, and had mycobacterial cultures and fingerprin ting performed. In-depth interviews were conducted on all persons with DNA fingerprinting. RESULTS: AFB smears were performed on 1424 individuals, 124 of whom were mi crobiologically confirmed. Of the 95 cases for whom bacterial DNA fingerpri nts were available, 38 were in clusters. The largest cluster involved seven individuals who were members of a social network centered on a series of u nlicensed bars. CONCLUSION: This population-based molecular epidemiologic study showed that a focus of transmission within a social network accounted for one fourth o f transmission which rapidly progressed to disease. These observations rais e questions about the potential benefit of targeted tuberculosis control in terventions in health jurisdictions approaching WHO-defined DOTS benchmarks .