The main five types of viral hepatitis: an alphabetical update

The rapidly increasing knowledge in the field of viral hepatitis warrants regular updates. Clinical studies with new hepatitis A vaccines have shown that they are safe, well-tolerated, and effective. Several reports on hepatitis B virus (HBV) variants have appeared. Surface antigen mutants may have an important influence on vaccine prophylaxis because existing vaccines may not protect against infection with these variants. Hepatitis D virus is a circular RNA virus that requires the presence of HBV for successful infection. The requirements for the dual expression of these viruses are unknown and their relation is complex. Hepatitis C virus (HCV) is a RNA virus that has homology with the flaviviridae. This is a rather common agent in most populations studied and often causes chronic infection but little is known about its spread. Hepatitis E virus is a RNA virus which is usually spread by contaminated water in developing countries. The disease causes high mortality in pregnant women. The existence of further viral hepatitis agents have been suggested but hard data confirming this is so far lacking.