Hepatitis C virus (HCV) is now known to be the major cause of parenlerally transmitted non-A, non-B hepatitis. Until the virus was characterized, diagnosis was made by exclusion of all other known causes of hepatitis. Antibody to HCV is found in over 80% of patients with well documented non-A, non-B hepatitis. The worldwide prevalence of HCV is 0.2 to 2% in blood donors and up to 80% in intravenous-drug users. In a large percentage of HCV cases, transmission is by transfusion and other parenteral means such as sharing of needles, occupational exposure to blood and hemodialysis. However, in dose to half of HCV infections, the route of transmission is unknown. HCV establishes a chronic infection in 50 to 80% of cases.
Chronic infection is often asymptomatic even in the presence of liver damage discernible on biopsy. Chronic HCV is characterized by fluctuating alanine aminotransferase levels and recognizable changes in liver histology. Chronic infection can lead to cirrrhosis and hepatocellular carcinoma.
Cloning of the viral genome made it possible to develop serologic assays even though the virus had not been visualized by electron microscopy or grown in cell culture. The following diagram shows the map of the putative functional regions of the HCV genome and derivations of the HCV antigens.