Viral hepatitis: from A to E, and beyond?
Identification of hepatitis viruses A-E has enabled researchers to investigate the epidemiology, pathogenesis, sequelae, and possible means of prevention of these infections. This knowledge also provides a basis for further study of the pathological significance of candidate hepatitis viruses. With improvements in hygiene in many parts of the world, hepatitis A virus infection has decreased markedly. However, this success has the unintended consequence of rendering a large percentage of the younger population susceptible to hepatitis A virus infection. Fortunately, effective active immunization for hepatitis A virus is now available. Hepatitis B remains a common condition, especially in Asia and Africa which have high prevalences of chronic infection. Chronic hepatitis B carriers serve as reservoirs of infection for the community and are at risk of chronic liver disease and hepatocellular carcinoma. A mass immunization program in Taiwan has been remarkably successful in reducing the prevalence of chronic hepatitis B infection. Genotypes of the hepatitis B viruses may be associated with the severity of liver disease and the responses to therapies. Hepatitis C is another important cause of death worldwide. The infection easily becomes refractory and the chronicity contributes to the development of cirrhosis and hepatocellular carcinoma. Although no effective immunization is currently available for hepatitis C, it can be controlled by preventative measures and recently developed interferon-based treatments, especially in combination with ribavirin. The prevalence of hepatitis D has markedly decreased in the last decade and new cases are now rarely encountered. Hepatitis E is endemic in limited areas and travel to these areas appears to be the main risk factor for contracting the infection. Several new candidate hepatitis viruses have been identified, including GB virus-C, TT virus, and SEN virus, but none of these has been shown to cause hepatitis, and they may be passenger viruses.
Chen
Ding Shinn
DS
Department of Internal Medicine and Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.
D014943:Global Health; D006525:Hepatitis, Viral, Human / Q000453:epidemiology* / Q000628:therapy* / Q000635:transmission; D006801:Humans; D012307:Risk Factors