Overview of substance abuse and hepatitis C virus infection and co-infections in India.

Hepatitis C virus (HCV) infection can have devastating long-term sequelae. It is very common in injecting drug users (IDU) worldwide. India has a huge number of substance abusers, with an estimated 1.1 million IDU. Research on HCV prevalence in IDU and especially other substance use is sparse. This review identified 15 such studies. Some of these also studied prevalence of hepatitis B virus (HBV) and human immunodeficiency virus (HIV) infections and co-infection rates. The summary findings indicate that there are pockets of very high HCV seroprevalence (60-90%), otherwise the range is moderate (30-50%), though, in real terms, it still indicates the appreciable magnitude of the problem that may emerge as an epidemic if it goes unheeded. HCV infection seems to be more common in IDU than HBV and HIV infections, again pointing toward the urgent need to prioritise this area. Co-infection rates are low in most of the few studies available, but clearly more studies are needed. There is a glaring paucity of studies on risk behaviours that can be linked meaningfully to HCV infection and its consequences. The urgent future research needs in this important area are highlighted.