Geographic distribution of human immunodeficiency virus markers in parenteral drug abusers

Drug abuse treatment programs in six regions of the United States collaborated in a study aimed at monitoring trends in the seroprevalence of human immunodeficiency virus (HIV) antibodies. The wide disparities in HIV seroprevalence in the face of similarities in drug using behavior have important implications for prevention. In the New York City area (Harlem, Brooklyn), 61 per cent of samples (N = 280) obtained in late 1986 were positive, up from 50 per cent of samples (N = 585) in early 1985. In Baltimore, Maryland, 29 per cent of samples (N = 184) representing 11 programs were positive. In contrast, samples from programs distant from the Northeast corridor had far lower rates: Denver, Colorado 5 per cent (N = 100); San Antonio, Texas 2 per cent (N = 106); Southern California, 1.5 per cent (N = 413); and Tampa, Florida, 0 per cent (N = 102). Contrary to expectations, there was no corresponding difference in reported lifetime needle sharing experiences, which ranged from 70 per cent in New York to 99 per cent in San Antonio. HIV seropositivity was associated only with geographic location and ethnicity; however, because needle sharing is practiced by parenteral drug abusers in areas where seroprevalence is still relatively low, these areas are potentially vulnerable to the same catastrophic spread seen in the Northeast. A window of opportunity exists where prompt, vigorous, and aggressive efforts at prevention could have major impact.