This review focuses on the features of HEV infection in humans and animals, as definitive or potential reservoirs for HEV, in Japan, and updates the current knowledge on the routes of transmission, including zoonotic routes, which are important for the maintenance and spread of HEV in Japan.

HEPATITIS E IS a form of acute hepatitis, which is caused by infection with hepatitis E virus (HEV), rarely leading to fulminant hepatitis with a high mortality rate. HEV principally replicates in the liver, is shed into the intestinal tract via the bile duct and is subsequently excreted into the feces. Therefore, the infection is transmitted primarily through the fecal–oral

route, and CX-4945 clinical trial the disease is highly prevalent in developing countries in Asia, Africa and Central America, where sanitation conditions are suboptimal.[1] Until very recently, MK-8669 HEV was regarded to be a rare “imported hepatitis” in industrialized countries, including the USA, European countries and Japan, and has consequently not attracted much attention in terms of research. However, the circumstances surrounding this disease have been very different since 1997. It has since become evident that indigenous HEV strains whose genotypes are different from those in endemic countries are circulating in industrialized countries, and that HEV infection is implicated in at least some cases of sporadic acute hepatitis or fulminant hepatitis whose etiology had been regarded to be unknown.[2-10] Furthermore, MCE it has been demonstrated

that HEV is the only zoonotic virus among the five known hepatitis viruses,[11-15] and that sporadic acute hepatitis E can occur through consumption of meat/viscera from domestic pigs or wild animals (boars and deer), which serve as reservoirs for HEV infection in humans.[16-20] Hepatitis E virus is a non-enveloped, small, spherical virus with a diameter of 27–34 nm (mean, 30), and is classified as a member of the genus Hepevirus of the family Hepeviridae.[21] The genome of HEV is a single-stranded, positive sense RNA composed of 7.2 kilobases (kb), and possesses a short 5′-untranslated region (UTR), followed by three open reading frames (ORF: ORF1, ORF2 and ORF3) and then a short 3′-UTR.[22] ORF1 encodes non-structural proteins involved in viral replication and viral protein processing, while ORF2 codes for a 660-amino-acid (a.a.) capsid protein and ORF3 encodes a small protein of 113–114 a.a. that is required for virion egress from infected cells and is associated with numerous cellular pathways.[23-26] There are four recognized genotypes of HEV that infect humans.