Hepatitis D Virus (HDV) or delta virus is a unique incomplete virus that requires hepatitis B virus (HBV) for its replication. The RNA genome is covered by an outer coat of hepatitis B surface antigen. HDV infection occurs worldwide but is endemic in certain regions including the Mediterranean basin, the Balkan peninsula, the former Soviet Union, parts of Africa and the Middle East and the Amazon basin of South America. In these regions, spread is typically intrafamilial and through sexual contact.
In non-endemic regions, such as North America, HDV infection is uncommon in the general population but does occur in intravenous drug users and persons with frequent exposure to blood products (e.g. hemophiliacs) as well as their sexual contacts.