ABSTRACT
Prevalence and determinants for human immunodeficiency (HIV) virus infection was assessed in 581 heterosexual intravenous drug users, recruited from public drug assistance centers in the northeast of Italy between 1984 and 1988. The overall seroprevalence rate for HIV antibody was 39% (95% confidence interval-CI-35-43%). HIV prevalence had risen from 32% in 1984-85 to 47% in 1986-88. Age was not associated with HIV infection risk, whereas gender was, women being at lower risk of infection than men (odds ratio-OR- = 0.7, 95% CI: 0,5-1.0). Seropositivity rates showed a strong east-west geographical gradient: intravenous drug users living in the western part of the study area had a nearly sevenfold higher risk of infection (95% CI = 4.4-13.9) than those living in the eastern part. Sharing of drug injection equipment was by far the most important risk factor. IVDUs who reported to always share injection equipment had a fourfold higher risk of HIV infection, as compared with those who never did (95% CI = 1.6-12.7). The duration of drug addiction (odds ratio = 2.6), the use of heroin in high-incidence cities (odds ratio = 2.3) and of cocaine in addition to heroin (odds ratio = 1.5) and the practice of prostitution (odds ratio = 2.3) were also important determinants of HIV infection. Over the study period, the odds ratios associated with area of residence decreased, whereas those associated with the use of heroin in high-incidence cities and with prostitution increased.
