Large decline in HIV infection prevalence among injection drug users in Chicago, 1988–2007

Objective: To examine long-term HIV seroprevalence trends among injection drug users (IDUs) in Chicago. Methods: We compared baseline HIV antibody prevalence from four studies of IDUs in Chicago conducted between 1988 and 2007. Recruiting periods and sample sizes are as follows: NADR, 1988 (n=850), CIDUS-I, 1994-1995 (n=794), Needle Exchange Evaluation, 1997-2000 (n=901), and SATH-CAP, 2005-2007 (n=2716, of whom 793 are IDUs). Participants were recruited from street settings, a needle exchange program, and through snowball sampling techniques. IDUs 18 years of age and older were eligible for all but CIDUS-I, which had an upper age limit of 50 years. Participants in all studies completed surveys and provided biological specimens assessed for antibodies to HIV. The NADR study included an examination of participant mortality. Results: HIV prevalence of IDUs at baseline for the four studies was: NADR, 24.6%, CIDUS-1, 18.1%, Needle Exchange Evaluation, 16.3%, SATH-CAP, 9.4%. HIV prevalence among SATH-CAP non-IDUs was 7.9%. Mortality among NADR participants after 8 years was 23%, with 39% of deaths attributed to HIV/AIDS. Conclusion: HIV prevalence among IDUs in Chicago has declined and is converging with that of noninjecting drug users. The decline in HIV prevalence likely is the product of high mortality rates early in the epidemic, behavioral changes in the wake of targeted risk reduction interventions, greater access to sterile syringes, and fewer African Americans initiating drug injection.