Continuing injecting risk behaviour: results from the Amsterdam Cohort Study of drug users

Aims. To give a detailed description of injection-related risk behaviours, and to estimate the relative importance of these behaviours with regard to HIV transmission. Design. The present study was part of the Amsterdam Cohor t Study of drug users. Setting. In Amsterdam, a city with extensive prevent ive measures, large HIV-risk reductions have taken place, but no further de creases have occurred since 1991. Participants and measurements. A derailed questionnaire on injecting risk behaviour was completed by a cross-section of participants in 1992/93 (n = 168). Among 48 HIV-seroconverters, a quest ionnaire was completed concerning possible HIV-transmission route. Findings . Of 96 HIV-negative participants, 23% deliberately borrowed a used syringe , 18% reported possible "accidental" borrowing, 9% front/backloading, 4% si multaneous injection, and 32% possible sharing of ancillary equipment. Of d eliberate borrowers, 64% borrowed from a person with unknown or positive HI V serostatus, and 81% did not appropriately clean the equipment; 79% borrow ed in the absence of serious withdrawal symptoms. Risk factors differed for deliberate and 'accidental' borrowing Among the HIV seroconverters, the mo st likely transmission route was borrowing in 29% of cases, front/backloadi ng in 8%, borrowing or front/backloading in 21%, unprotected sexual contact in 23% (mainly with regular partner) and either injecting or sexual risk i n 13%. Women were much more likely to report sexual transmission (p = 0.016 ). Borrowing was admitted by 43% before, and 64% after awareness of HIV-ser oconverion. Conclusions. As the injecting risk is high, usually deliberate, and often in the absence of withdrawal symptoms, further prevention seems difficult. Although deliberate borrowing is the main risk for HIV seroconve rsion, unprotected sexual contacts and front- and backloading may be more i mportant than previously thought in Amsterdam. Under-reporting of borrowing is probably substantial, but does not alter the above conclusions.