<qa>  What is the current threat to public health that HCV produces?There is a stark paucity of data published concerning reinfection rates post successful treatment for HCV in currently injecting drug users. The investigators research will focus in this important area and provide desperately needed evidence to increase confidence in treating this population who carry the burden of the disease. Treating larger numbers of individuals in this population will reduce the incidence of HCV in injecting drug users and therefore reduce the overall prevalence of the disease. This will reduce the current threat to public health that HCV produces. 