The prevalence and incidence of HIV among injection drug users: A five year panel study

Six hundred and one injection drug users (IDUs) who attended drug treatment programs in Miami, Florida, were enrolled in a panel study to determine the prevalence and incidence of human immunodeficiency virus (HIV) and associated risk factors. A structured questionnaire which elicited injection and sexual behaviors was administered and blood was obtained by venipduncture. All participants were reassessed at six month intervals for 5 years. The baseline prevalence of HIV was 16.3%. African–Americans had a prevalence of HIV (37.1%) that was significantly higher than that of non-Hispanic whites (7.6%); the prevalence of HIV among Hispanics was 27.2%. Persons who were more than thirty years of age were more likely to test HIV positive (17.8%) than were younger participants (9.7%). The annual incidence per 1000 person-years of exposure for the 503 initially seronegative participants was consistently low for each year of the study. The 5 year incidence was 4.1 per 1000 person years; 7.5 for men and 1.7 for women, 7.5 for African–Americans and 3.8 for non-Hispanic whites. No Hispanic participants seroconverted. Multivariate logistic techniques were used to identify the independent risk factors for HIV prevalence. Earlier injection, ethnicity, and income were independently associated with HIV serostatus. A history of a sexually transmitted disease was marginally associated with HIV prevalence. Low incidence probably is a function of the reduction of risk behavior that occurred over the course of the study and the stage of the epidemic.