The estimated prevalence and incidence of HIV in 96 large US metropolitan areas.

OBJECTIVES: This study sought to estimate the size and direction of the human immunodeficiency virus (HIV) epidemic in US metropolitan statistical areas (MSAs) with populations greater than 500,000. METHODS: A "components model" from review of more than 350 documents, several large datasets, and information from 220 public health personnel was used. Data review focused on injection drug users, men who have sex with men, and high-risk heterosexual men and women. RESULTS: In the 96 MSAs, there are, broadly, an estimated 1.5 million injection drug users, 1.7 million gay and bisexual men, and 2.1 million at-risk heterosexuals, and, among them, an estimated 565,000 prevalent and 38,000 incident HIV infections. This implies about 700,000 prevalent and 41,000 new HIV infections yearly in the United States. Roughly half of all estimated new infections are occurring among injection drug users, most of them in northeastern cities, Miami, and San Juan. Gay and bisexual men still represent most prevalent HIV infections, although incidence--except in young and minority gay men--is much lower now than it was a decade ago. Relatively high prevalences of HIV in at-risk heterosexual persons in several cities indicate the potential for an increase in transmission among them. CONCLUSIONS: This review and synthesis outline the comparative epidemiology of HIV in major US cities and identify populations for interventions.