INCIDENCE OF BLOODBORNE VIRUS-INFECTION AND RISK BEHAVIORS IN A COHORT OF INJECTING DRUG-USERS IN VICTORIA, 1990-1995

Objective: To assess changes in risk behaviours for transmission of bl oodborne viruses and incidences and prevalences of these Viruses in af ield-recruited cohort of injecting drug users. Design: Prospective lon gitudinal cohort study. Setting: Metropolitan and rural Victoria, June 1990 to December 1995. Subjects: 626 current injecting drug users (i. e., who had injected drugs within the previous 12 months). Main outcom e measures: Seroconversion to HIV and hepatitis B and C viruses (HBV a nd HCV); risk behaviours for infection. Results: HIV incidence was ver y low (0.2 per 100 person-years). HCV incidence was high (10.7 per 100 person-years), but fell throughout the study, although the downward t rend did not reach statistical significance. HBV incidence was moderat e (1.8 per 100 person-years) and did not fall. Prevalence of risk beha viours, notably sharing needles and syringes, decreased significantly. Conclusions: Significant change has occurred in the risk behaviours o f the cohort, confirming results of cross-sectional studies of injecti ng drug use. This change may be responsible for the apparent decline i n HIV and HCV incidence. Further studies are needed to monitor the inc idence of bloodborne viruses in injecting drug users. Efforts to decre ase risk of transmission should continue.