Molecular biology of hepatitis viruses

The five human hepatitis viruses, A to E, belong to five different virus families with distinct genomic structures and replication strategies. Hepatitis A virus is an enteric picornavirus that is readily transmitted under conditions of crowding and poor sanitation. Hepatitis B virus (HBV) is transmitted primarily from blood or blood-derived products. After the discovery of HAV and HBV and the development of early diagnostic tools in 1974, Hepatitis C virus was realized that a substantial number of cases of transfusion-associated acute and chronic hepatitis could not be accounted for by these two viruses. Hepatitis D virus was first detected as a novel antigen, termed hepatitis delta antigen, present in the nuclei of hepatocytes of some HBV carriers in Italy experiencing episodes of acute hepatitis. Hepatitis E virus is responsible for major outbreaks of acute food-borne hepatitis in tropical resource-poor countries, particularly in Asia, Africa, and Central America.