Preliminary estimates of human immunodeficiency virus prevalence and incidence among cocaine abusers of Porto Alegre, Brazil.

A sample of 193 southern Brazilian inner-city cocaine abusers was studied to assess the prevalence of human immunodeficiency virus (HIV) infection. Following the exclusion of those who were seropositive from the intake sample, a cohort of 138 HIV-negative cocaine abusers was followed for 18 months to assess seroincidence rates and the associated characteristics. HIV status, drug use, sexual risk behaviors, and presence and severity of medical and psychiatric symptoms were collected at intake using a Brazilian version of the Risk Assessment Battery, the Addiction Severity Index (ASI), Symptom Check List-90 (SCL-90), and Beck Depression Inventory (BDI); this was repeated at 6-, 12-, and 18-month intervals. The overall seroprevalence was 28.5%, and the variables associated with HIV seropositivity were age older than 25 years, being single, having less than 8 years of education, and having injected cocaine at least once. Although follow-up procedures were difficult to implement due to sample characteristics, we obtained data from 82.6% of the participants for at least one follow-up and for 57% at all follow-up windows. Most participants showed high scores on the Beck Depression Inventory (mean of 20.6 +/- 13.9) and Symptom Check List-90 (mean of 106.4 +/- 91.9). There were 8 seroconversions in the 18-month period, yielding an incidence rate of 5.03/100 (confidence interval [CI] 2.2-9.7) person-years at risk. None of the seroconverters reported recent cocaine injection, and only 14.5% of the overall sample reported ever injecting cocaine, which suggests that another significant mode of transmission via sexual behavior should be considered as well. Each of these findings has important implications for the design of preventive interventions.