Objective: Evidence of ongoing hepatitis C (HCV) transmission among injecting drug users (IDUs) suggests a need for a better understanding of seroconversion characteristics among new IDUs and other vulnerable subgroups. This study aimed to determine incidence of HCV and associated risk factors among new IDUs in Sydney.
Methods: IDUs who had injected drugs in the past six months and who were unaware of their antibody HCV status or knew their serostatus to be negative were recruited through street-based outreach, methadone clinics and needle and syringe programs in south-western Sydney. Anti-HCV negative IDUs (n = 215) were enrolled and followed-up at 3-6 monthly intervals. New IDUs (n = 204) were defined as aged below 30 years or injecting for < or = 6 years at baseline.
Results: A total of 61 seroconversions were observed and incidence was 45.8 per 100 person years. Independent predictors of seroconversion were duration of injecting < 1 year (IRR = 3.10; 95% CI 1.47-6.54), female gender (IRR = 2.0; 95% CI 1.16-3.45), culturally and linguistically diverse background (CALDB) (IRR = 2.03; 95% CI 1.06-3.89) and intravenous cocaine use (IRR = 2.37; 95% CI 1.26-4.44). While new IDUs shared common risk factors, strong associations were observed between HCV seroconversion and sharing syringes, sharing other injecting equipment and backloading in CALDB new IDUs.
Conclusion: Incidence of HCV infection among new IDUs in Sydney is unacceptably high.
Implications: Extremely high rates of incident infection among newly initiated CALDB IDUs indicate an urgent need for enhanced policy and resource commitments to reduce the vulnerability of this group to HCV and other blood-borne infections.