[AIDS epidemiology and prevention in i.v. drug addicts].

The incidence of AIDS cases in intravenous drug abusers is growing faster than in other risk groups, in Switzerland as well as in Europe in general. By end of May 1988, 27% of all AIDS cases registered nationally were injecting drugs. The prevalence of HIV antibodies is known from selected samples only, on the basis of voluntary testing. In 1986, among all intravenous drug users in residential treatment nation-wide, 90% were tested and thereof 55% seropositive. In a sample of drug abusers in out-patient treatment in Zurich in 1987, seropositivity was documented for 42% of male and 63% of female patients. According to registered AIDS cases, there is no differential risk for both sexes. Duration of intravenous drug abuse is the only relevant risk factor so far. Preventive change in risk taking behaviour is a minimalization of utilizing contaminated syringes/needles and a minimalization of unprotected sex (safer sex by regular use of condoms). An analysis of published data demonstrates that dissemination of information and availability of syringes/condoms are a pre-requisite for behaviour change, but by no means sufficient in order to elicit behaviour change. Drug abusers engaged in out-patient/residential treatment are available in high proportions for voluntary testing and for the intended behavioural changes. It is therefore of primary preventive interest to engage as many intravenous drug abusers as possible in treatment. Apart from drug-free residential treatment, out-patient treatment using Methadone provides positive results, whereas compulsory measures are considered to be of doubtful value.