We experienced a case of autochthonous hepatitis E by hepatitis E virus (HEV) genotype 4. The phyloge-netic tree analysis indicated that the HEV isolate ob-tained from the patient was segregated into the HEV subgenotype 4a (HEV-4a) cluster. The patient had no history of travel abroad, e.g., to China, where HEV-4a strains are endemic. The source and the route of the HEV-4a infection were unknown. Strains of HEV-4a may be indigenous to Japan despite remaining unde-tected to date, either in swine or wild animals. Addi-tional HEV subgenotypes circulating in swine and wild animals in Japan require investigation to reveal the characteristics of HEV-4a infection in autochthonous cases in Japan.
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