Irish injecting drug users and hepatitis C: the importance of the social context of injecting.

Background: The incidence of hepatitis C (HCV) infection among injecting drug users (IDUs) in Dublin is particularly high by international standards. The most robust predictor of an IDU's HCV status is his or her total number of lifetime injecting episodes. It has been proposed that participation in specific unsafe injecting practices is the principal contributor to this accumulated risk. We sought to test this hypothesis. The relationship between social context of injecting and HCV status was also examined.

Methods: We conducted a cross-sectional survey of IDUs recruited from treatment settings in Dublin. Participants had injected in the preceding six months and had not previously been tested for HCV. A structured interview was conducted.

Results: HCV testing was performed on 159 IDUs, and 61% were antibody positive. The three characteristics that were significant independent predictors of a positive test result were increased total number of lifetime injecting episodes, closer social relationships with other IDUs, and injecting in the home of other IDUs. Frequency of recipient syringe sharing (i.e. borrowing used syringes from other IDUs), backloading, and sharing of injecting paraphernalia were not independently associated with infection.

Conclusions: We found that the robust association between HCV infection and number of lifetime injecting episodes was not explained by increased unsafe injecting practices. The socialized nature of heroin injecting in Dublin is contributing to the HCV epidemic in this population. Our findings suggest that accidental and unnoticed sharing of injecting equipment may be an important contributor to an IDU's increasing risk of infection over time.