Prevalence and risk factors of HIV infections among drug users and drug-using prostitutes in Amsterdam

Abstract

In December 1985 we started a study to determine the prevalence and risk factors of HIV infection among drug users and drug-using prostitutes in Amsterdam. Recruitment took place at methadone posts (not drug-free; i.e. a low-threshold programme on which some drug users continue to use hard drugs, but at a lower level) and the weekly evening sexually transmitted diseases (STD) clinic for drug-addicted prostitutes. Three hundred and ten drug users have so far been tested and interviewed. Eighty-one per cent reported intravenous drug use; 83% of the 166 females and 15% of the 144 men reported prostitution. Female prostitutes practised mainly vaginal and orogenital intercourse and reported frequent use of condoms (89% of vaginal and 64% of orogenital contact). Male prostitutes practised mainly orogenital and manual contact. At entry 88 of the 310 (28%) were HIV-antibody-seropositive; 85 of these 88 were intravenous drug users and three were male homosexuals. HIV-antigen was detected in two seropositive and one seronegative intravenous drug-user. Antibodies to HTLV-I were found in four out of 308. Risk factors independently associated with HIV-antibody seropositivity among intravenous drug users were: frequency of borrowing used needle or syringe, date of first intravenous drug use, recent intravenous drug use, time living in Amsterdam and German nationality. Of medical history data, an attack of herpes zoster in the previous 5 years had the greatest value in the prediction of the presence of HIV antibodies (relative risk 20.90; 95% confidence interval 2.41 – 167.27). While the prevalence of HIV infection among drug users is increasing in Amsterdam, it seems to be occurring at a slower rate than in other European cities. It is encouraging that the majority (74%) of intravenous drug users in this study was aware of the danger of needle and syringe sharing and significant changes in lifestyle regarding the safer use of intravenous drugs were found. How this change will influence the further spread of HIV among this group remains to be seen.