Hepatitis E virus: the current scenario

Viral hepatitis, caused by any of the five hepatotropic viruses, i.e., hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), and hepatitis E virus (HEV), represents a major health problem worldwide. Among the viruses, HEV is now established as the major etiological agent of enterically transmitted non-A, non-B hepatitis. The first well-documented epidemic of hepatitis E infection in India was the epidemic of 1955-56 in New Delhi, affecting a total of 29 000 people; this occurred due to fecal contamination of drinking water. Although originally considered to be an epidemic of hepatitis A, retrospective testing of the stored sera from the affected patients suggested that a novel infectious agent was responsible. 1 Since the early 1990s, following the identification and sequencing of its etiological agent, the disease became known as hepatitis E and its agent as hepatitis E virus. A high case fatality rate averaging around 20% in pregnant women, particularly in the third trimester, is a characteristic feature of HEV infection. HEV is regarded as the major etiological agent of enterically transmitted non-A hepatitis in India. HEV is responsible for both sporadic and epidemic outbreaks of acute hepatitis in developing countries, leading to a self-limiting disease. The global burden of HEV infection is more due to sporadically transmitted hepatitis E cases than to cases due to epidemic hepatitis E. Based on the 2010 global burden of diseases study, it has been estimated that as many as 20.1 million people were infected with HEV genotypes 1 and 2 in 2005, in nine regions. This represents 71% of the world's population, with 3.4 million symptomatic cases, 70 000 deaths, and 3000 stillbirths. he death rate was higher among symptomatic pregnant women that among symptomatic non-pregnant women. EV has been classified as the type species of the new genus Hepevirus in the family Hepeviridae. 7 Study of the molecular biology of HEV was significantly advanced with the establishment of an efficient cell culture system 8 and an effective vaccine, 9 but we still lack a reliable diagnostic procedure. However, anti-HEV antibody assays are widely available in European and Asian countries. Recent findings in HEV molecular biology, diagnosis, and pathogenesis are reviewed here.