Quantitative Impact of Human Immunodeficiency Virus Infection on Tuberculosis Dynamics

Abstract

Human immunodeficiency virus (HIV) infection has a major but unquantified impact on the risk of tuberculosis. To quantify the impact of HIV infection on the number of tuberculosis cases in San Francisco. We studied all patients reported with tuberculosis in San Francisco from 1991 to 2002. The initial isolates of Mycobacterium tuberculosis were genotyped using IS6110 restriction fragment-length polymorphism genotyping as the primary method, and clustered cases (identical genotype patterns) were identified. We determined the case number, case rate, and the fraction of tuberculosis attributable to HIV infection. Of 2,991 reported tuberculosis cases, 2,193 (73.3%) had a genotype pattern of M. tuberculosis available. Genotypic clusters with at least one HIV-positive person were larger, lasted longer, and had a shorter time between successive cases relative to clusters with only HIV-uninfected persons (P < 0.00005, P = 0.0009, P = 0.018, respectively). Overall, 13.7% of the tuberculosis cases were attributable to HIV infection and an estimated 405 excess tuberculosis cases occurred. During a period encompassing the resurgence and decline of tuberculosis in San Francisco, a substantial number of the tuberculosis cases were attributable to HIV infection. Coinfection with HIV amplified the local tuberculosis epidemic.