We investigated for HEV-RNA in serum samples obtained from 15 wild boars in the Iriomote Island of Okinawa Prefecture, and 2 of 15 (13.3%) were positive for HEV-RNA. Sequence analysis of a part of ORF1 region (326 nt) indicated that the 2 isolates from the Iriomote's boars (wbOK126 and wbOK128) were fairly remote from known strains: none of known sequences showed a nucleotide similarity greater than 90%. In phylogenetic tree analyses, however, the wbOK126 and wbOK128 isolates segregated to genotype 4, and formed a cluster with Chinese strains, rather than with Japanese ones interestingly. Regarding the geographical situation of the Iriomote Island (i.e., nearer to China than to Japan's main lands), our present results provide a clue to the origin of Japan-indigenous HEV strains.
