GB virus C/Hepatitis G virus

Hepatitis G virus (HGV) is a positive, single-strand RNA virus that has been classified in the family Flaviviridae. The 5'-untranslated region (UTR) of the HGV genome is lengthy and does not share any significant primary and secondary RNA structures with the 5'-UTR of hepatitis C virus (HCV). The internal ribosome entry site has extraordinarily weak activity. The HGV genome does not seem to encode a nucleocapside protein analogous to HCV. Blood-borne transmission is presumed to be the commonest mode of transmission of the virus. Current infection with HGV is diagnosed by detection of HGV RNA by the polymerase chain reaction (PCR), and past infection with HGV is detectable by testing anti-HGV E2. HGV is distributed worldwide, but its prevalence varies widely from one population to another. Although the prevalence of HGV in association with acute and chronic hepatitis is higher than that in the general population, further prospective studies are needed to demonstrate its relative significance in causing hepatitis and other disease. The major unresolved biological issue at the moment is its hepatotropsim and site of propagation. Recent progress demonstrates that HGV replicates in lymphocytes rather than hepatocytes. HGV may be pathogenic under special conditions, but does not influence carcinogenesis.