Hepatitis delta virus genotype IIb predominates in an endemic area, Okinawa, Japan

Hepatitis delta virus (HDV) infection is relatively common in the Miyako Is lands, Okinawa, Japan, where the infection has been reported to be associat ed with low pathogenicity. HDV RNA extracted from each of 6 patients with H DV-related chronic liver disease living in the islands was amplified by rev erse transcription-polymerase chain reaction and examined genetically to de termine the HDV genotype. All isolates from the 6 patients were classified as genotype II by the neighbor-joining method. However, these isolates had relatively low homology (75-81%) to the HDV genotype II isolate reported fr om Japan, and showed relatively high identity (83-95%) to the novel genotyp e II isolate (HDV genotype IIb) recently reported from Taiwan. Phylogenetic analysis showed that the 6 isolates form a novel group within HDV genotype II. Furthermore, there was notable variation in sequence among the 6 isola tes compared with the relatively close clustering of HDV isolates within li mited areas (e.g., United States, Archangelos, Turkey, Albania, Peru). HDV genotype II in the Miyako Islands is therefore unique, and HDV infection ma y have been introduced at a relatively early time in this area. J. Med. Vir ol. 55:366-372, 1999. (C) 1999 Wiley-Liss, Inc.