Hepatitis E and its emergence in non-endemic areas.

In areas with a tropical or subtropical climate and poor sanitary conditions, hepatitis E is the major cause of enterically transmitted non-A, non-B hepatitis, and is responsible for both waterborne outbreaks of variable magnitude and sporadic cases of acute hepatitis. The causative agent is the hepatitis E virus (HEV), a non-enveloped, single-stranded, positive-sense RNA molecule of approximately 7.2 kb in length. Recently, HEV strains have been isolated from swine in industrialized countries. In addition, cases of acute hepatitis due to novel HEV variants have been reported in humans without recognized risk factors for hepatitis E in the US, Japan and Europe. Some of the novel strains were found to be closely related to swine HEV isolates from the same area, suggesting that hepatitis E is a zoonotic disease. Thus hepatitis E is becoming an issue in countries where HEV is not, traditionally, believed to be endemic. This review summarizes the current knowledge on the transmission, structure and biology of the virus as well as diagnosis of the infection, and describes the present status in areas with a low incidence of acute hepatitis E.