HEPATITIS-C VIRUS-INFECTION AMONG A COHORT OF VICTORIAN INJECTING DRUG-USERS

Objective: To describe the epidemiology of infection with hepatitis C virus (HCV) among injecting drug users (IDUs) in Victoria. Design and subjects: Subjects were current IDUs from a wide spectrum of age, sex and social background, enrolled in a prospective study of injecting dr ug use. They were contacted by peer workers through their social netwo rks and through community agencies and prisons, and were regularly fol lowed for interview and blood collection in the field. Sera were teste d for presence of antibody to HCV (anti-HCV), for the presence of HCV RNA directly in serum, and for measures of liver function. The results were correlated with demographic variables. Setting: Rural and metrop olitan Victoria. Main outcome measures: Presence of anti-HCV and demon stration of HCV RNA. Results: Two-thirds (68%, 206/303) of the current cohort of IDUs were seropositive f or HCV, risk being particularly as sociated with duration of injecting, and independently for men with op iate use and prison history, and for women with a history of methadone therapy. HCV RNA was detected in 48% (76/160) by polymerase chain rea ction (PCR); 61% (74/122) of these subjects were HCV seropositive and 5% (2/38) seronegative. Of 32 HCV seronegative subjects followed for a mean period of 291 days, five seroconverted to HCV, an incidence of 2 0 infections per 100 person-years. Those who seroconverted were older, more likely to be male, had been injecting longer, more often reporte d opiate use, and were more likely to be based in the country. Serum l iver enzyme levels were higher and more likely to be abnormal in HCV s eropositive than seronegative subjects, and were highest in those sero positive subjects in whom HCV RNA was detected.Conclusions: This popul ation of IDUs has a very high rate of exposure to HCV, related to dura tion of injecting and independently to opiate use and prison history, perhaps reflecting increased risk in particular social networks. There is evidence of high rates of carriage of HCV, of continuing transmiss ion of HCV, and of ongoing liver disease among these IDUs. If these ID Us are at all representative of all IDUs in Australia, we estimate tha t 80000 current and former IDUs may be at risk of chronic liver diseas e from HCV, and that 8000-10000 new infections may be occurring each y ear. Two subjects who were seronegative had HCV RNA detectable in sera . These data have important implications for screening programs and do cument the need for further measures to prevent spread of blood-borne viruses including HIV among IDUs.