Evidence for spread of the human immunodeficiency virus epidemic into low prevalence areas of the United States.

Reports of an increased proportion of AIDS cases occurring in small and medium-sized cities suggest that the HIV epidemic may be spreading into locations that were previously characterized by their low HIV antibody prevalences. Studying the question of the geographic spread of the HIV infection epidemic (rather than the AIDS epidemic) has been difficult largely because most serial seroprevalence data have been gathered from cohorts of high risk individuals (e.g., homosexual/bisexual cohorts) in New York City, San Francisco, and other geographically circumscribed areas. The U.S. military applicant HIV screening data were used in the current report to examine rates and 24 month temporal trends in geographic areas characterized by their HIV endemicities. The data examined concern the seven most populous states and four hyperendemic metropolitan areas located within those states (New York City, Miami, Houston, and San Francisco). In the nonepidemic regions, seroprevalence rates increased among black and white applicants. In the four epidemic urban areas, only young black applicants had higher HIV seroprevalence rates during the second 12 month period. Six of the seven nonepidemic regions had positive HIV seroprevalence trends, and these trends were significant in Florida, California, Texas, Illinois, and Ohio. The increases in these regions were greater for young blacks (30% excess for year 2 vs. year 1) compared to young whites (12% excess for year 2 vs. year 1). These data provide evidence of birth year specific increases in seroprevalence over time occurring in presumed low HIV prevalence areas. These increases cannot be due to, but are observed in spite of, biases associated with increasing self-selection over time.