We experienced 4 cases (2 in 2005 and 2 in 2006) of hepatitis E, where the patients developed their disease one or two months after eating meats and/or entrails of wild boars captured in Aichi prefecture, Japan. All 4 were middle-aged men, and 3 had a history of significant alcohol drinking. One of them developed hepatic coma, received corticosteroid administration and plasma exchange therapy, and survived eventually. Another patient also suffered severe form of hepatitis but not encephalopathy. Hepatitis E virus (HEV) of genotype 4 was detected in all. Interestingly, the nucleotide sequences of HEV from the 4 patients showed quite a high degree of similarity to each other (98.8-99.8%) as well as to those from wild boars in Aichi (99.1-100%), despite showing only a significantly lower similarity to those reported as genotype 4 from other areas in Japan (85.4-89.3%). These findings suggest that an indigenous strain of HEV genotype 4 is now spreading in Aichi, and warrant a need for immediate countermeasures.
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