Analysis of human and swine hepatitis E virus (HEV) isolates of genotype 3 in Japan that are only 81-83% similar to reported HEV isolates of the same genotype over the entire genome

Full-length sequences were determined for a human hepatitis E virus (HEV) isolate (HE-JA04-1911) and two swine HEV isolates (swJ8-6 and swJ12-4) that belong to one of three clusters within genotype 3 in Japan and are close to Spanish isolates according to their partial sequences. The three HEV isolates were 89.7-92.9% identical to each other, but only 80.7-83.0% similar to 21 HEV strains of the same genotype isolated in Canada, Kyrgyzstan, the USA and Japan over their entire genome. On comparison with HEV isolates whose partial sequence is known, the HE-JA04-1911, swJ8-5 and swJ12-4 isolates segregated into a phylogenetic cluster consisting of human and swine HEV isolates in Japan and the UK, with identities of 89.8-100% and 87.9-92.4%, respectively. Genotype 3 HEV isolates were found to be markedly heterogeneous. The UK-isolate-like HEV strains in Japan may have originated from the UK via the importation of pigs since 1900.