Differences in contributing factors to tuberculosis incidence in US-born and foreign-born persons

To determine the factors contributing to tuberculosis incidence in the U.S. -born and foreign-born populations in San Francisco, California, and to ass ess the effectiveness of tuberculosis control efforts in these populations, we performed a population-based molecular epidemiologic study using 367 pa tients with strains of Mycobacterium tuberculosis recently introduced into the city. IS6110-based and PGRS-based restriction fragment length polymorph ism (RFLP) analyses were performed on M. tuberculosis isolates. Patients wh ose isolates had identical RFLP patterns were considered a cluster. Review of public health and medical records, plus patient interviews, were used to determine the likelihood of transmission between clustered patients. None of the 252 foreign-born cases was recently infected (within 2 yr) in the ci ty. Nineteen (17%) of 115 U.S.-born cases occurred after recent infection i n the city; only two were infected by a foreign-born patient. Disease from recent infection in the city involved either a source or a secondary case w ith human immunodeficiency virus (HIV) infection, homelessness, or drug abu se. Failure to identify contacts accounted for the majority of secondary ca ses. In San Francisco, disease from recent transmission of M. tuberculosis has been virtually eliminated from the foreign-born but not from the U.S.-b orn population. An intensification of contact tracing and screening activit ies among HIV-infected, homeless, and drug-abusing persons is needed to fur ther control tuberculosis in the U.S.-born population. Elimination of tuber culosis in both the foreign-born and the U.S.-born populations will require widespread use of preventive therapy.