Acute hepatitis due to hepatitis E virus genotype 1 as an imported infectious disease in Japan.

An 18-year-old Nepalese man was admitted due to general malaise and anorexia a month after coming to Japan. Laboratory tests showed elevation of transaminase and positivity for IgM anti-HEV antibody. Serum HEV RNA was detected by RT-PCR amplifications. An HEV genome phylogenetic tree, constructed using an 821-nucleotide sequence in the open reading frame 1, indicated that the genotype was 1. HEV genotype 1 is epidemic in South Asia, Africa and South America, and the incidence of acute hepatitis due to HEV genotype 1 is low in Japan. Thereafter, attention should be paid to HEV genotype 1 infection as an imported infectious disease.