Viral hepatitis type E is highly endemic in many developing countries, where large water-borne epidemics
caused by viral genotype 1 and – to a lesser degree - by genotype 2 cyclically occur, resulting in high morbidity
and mortality, especially among pregnant women. In developed countries, the disease is usually diagnosed
in travelers coming back from endemic countries, but an increasing number of sporadic locally acquired
hepatitis cases caused by genotype 3 and 4 have recently been reported. The wide-spread distribution of
HEV3 and HEV4 in domestic pigs, wild boars, deer, as well as in other mammals, suggests that infections
caused by these genotypes may have a zoonotic source. HEV3 infection can evolve to chronic infection in
immunosuppressed patients; in addition, it may be associated with neurological disorders and extrahepatic
manifestations. Two recently developed recombinant vaccines have proved to be safe and effective. One of
such vaccines has recently been licensed for use in China.
