TUBERCULOSIS TRANSMISSION IN CENTRAL LOS-ANGELES

Context.-Recent studies suggest that many tuberculosis cases in urban areas result from recent transmission. Delineation of the epidemiologi c links between patients is important to optimize strategies to reduce tuberculosis transmission. Objective.-To identify epidemiologic links among recently infected urban patients with tuberculosis. Design.-Pro spective evaluation of patients with tuberculosis. Setting.-Central Lo s Angeles, Calif. Patients.-A total of 162 patients who had culture-pr oven tuberculosis, Interventions.-Patients were prospectively intervie wed to identify their contacts and whereabouts. The IS6110-based and p TBN12-based restriction fragment length polymorphism analyses were per formed on Mycobacterium tuberculosis isolates. Patients whose isolates had identical or closely related restriction fragment length polymorp hism patterns were considered a cluster. Unconditional logistic regres sion was used to identify independent predictors of clustering. Main O utcome Measures.-Relationship of clinical and epidemiologic variables to clustering, Results.-A total of 96 (59%) of 162 patients were in 8 clusters, Only 2 of the 96 clustered patients named others in the clus ter as contacts, The degree of homelessness was an independent predict or of clustering, Compared with nonclustered patients, patients in 6 c lusters were significantly more likely to have spent time at 3 shelter s and other locations when at least 1 patient in the cluster was conta gious, and these locations were independent predictors of clustering. Among nonhomeless persons, clustered patients were significantly more likely than nonclustered patients to have used daytime services at 3 s helters, Conclusions.-(1) Traditional contact investigation does not r eliably identify patients infected with the same M tuberculosis strain , and (2) locations at which the homeless congregate are important sit es of tuberculosis transmission for homeless and nonhomeless persons. Measures that reduce tuberculosis transmission should be based on loca tions rather than on personal contacts.