Four cases of sporadic acute hepatitis E in Mie, Japan who were infected with European type genotype 3 hepatitis E virus

From 2004 to 2010, we have seen four cases of sporadic acute hepatitis E in nothern or central district of Mie Prefecture, Japan, who contracted infection of rare genotype 3 hepatitis E virus (HEV) strains. The HEV strains recovered from the four patients were 99.3-99.5% identical to each other in the 412-nucleotide sequence within ORF2 and homologous to those circulating in European countries such as Spain, United Kingdom, and the Netherlands, suggesting the long-term maintenance of the European type genotype 3 HEV strains in a restricted area in Japan. None of these four patients had histories of consuming uncooked or undercooked meat and/or viscera from infected animals and of travel to European countries, and the source of infectious origin remains unknown. These results warrant careful observation of clinical and subclinical HEV infection in this area and implementation of infection prevention measures in the future.