Incidence rate and risk factors for HCV seroconversion among injecting drug users in an area with low HIV seroprevalence.

We conducted a study on injecting drug users attending one of 3 drug treatment centres in Naples, to estimate HIV and hepatitis C virus (HCV) incidence rates and to identify risk factors for seroconversion. Incidence rates were estimated using as denominator the person-time of follow-up of participants who were negative for both HIV and HCV at enrollment and who were retested within 6-12 months. Information on risk factors was collected using a standardized questionnaire. A nested case-control analysis was performed comparing seroconverters with persistently HCV-negative individuals. None of the initially non-infected participants seroconverted for HIV, while the incidence rate for HCV infection was approximately 29 per 100 person-years. Analysis of risk factors showed that age > 28 years and injecting use of cocaine were associated with HCV seroconversion. The protective role of methadone treatment was also marginally significant. Our findings suggest that HCV infection may represent an important public health problem in areas with low HIV circulation. The identification of specific risk factors for HCV infection is needed to plan effective prevention strategies.