Does Information about IDUs' Injecting Networks Predict Exposure to the Hepatitis C Virus?

Background and Aims: Many previous studies have used cross-sectional approaches to measure associations between injecting drug users' (IDUs') characteristics and hepatitis C virus (HCV) status, and identified independent predictors of antibody to HCV (anti-HCV) positivity including duration of injecting, needle-sharing history and prior imprisonment. Although HCV transmission between IDUs occurs primarily through blood transfer during close physical interactions, the contribution of social network data to prediction of HCV status has not been previously assessed. Methods: 215 injecting drug users and their injecting network members were recruited in Melbourne, Australia between July 2005 and August 2006. Logistic regression was used to analyze behavioral and social network data for predictors of HCV exposure. Results: IDUs' HCV exposure status was independently associated with the age of first injection of their injecting network members (adjusted OR=2.82, P=0.019) and the HCV exposure status of those network members (adjusted OR = 6.17, P<0.001), in addition to several 'traditional' behavioral and lifetime variables. Conclusions: Patterns of exposure to the hepatitis C virus are influenced by the characteristics of members of IDUs' social networks. HCV RNA and/or antibody testing are an important part of any HCV prevention strategy for IDUs; increased availability of testing and sharing HCV status information within social networks would enable more IDUs to