Molecular epidemiology of chronic hepatitis C (HCV) virus

Hepatitis C virus (HCV) is a major etiologic causative agent of chronic hepatitis, cirrhosis with its attendant risks of hepatocellular carcinoma. Efforts to isolate the virus by standard immunologic and virologic techniques were unsuccessful and HCV was finally identified by direct cloning and sequencing of its genome. Although the virus was identified 15 years ago, its pathogenesis and replication are not fully understood. Progress in the molecular biology of HCV was achieved by expressing viral recombinant proteins in culture cells and utilizing recombination DNA techniques. An important feature of HCV is that the viral genomes display extensive genetic heterogeneity at the local as well as the global level. Within a host, the HCV genome population circulates as a 'quasi-species' of closely related sequences. Worldwide, a high degree of genetic variation exists resulting in at least six major genotypes of more distantly related subtypes. It has been reported, that the prevalence of each subtype varies in different geographical areas and that virus pathogenicity and sensitivity to interferon treatment, appear to vary with different subtypes.