Analysis of complete genome sequences of swine hepatitis E virus and possible risk factors for transmission of HEV to humans in Korea.

The hepatitis E virus (HEV) is an emerging zoonotic agent, for which pigs are the most important reservoir. Complete genome sequences of two swine HEV strains, designated swKOR-1 and swKOR-2, were determined via RT-PCR and RACE-PCR. The strains contained genomes composed of 7,222- and 7,221-bp excluding the poly(A) tails, respectively. The swKOR-1 and swKOR-2 strains were classified into subtype 3a of genotype 3 via phylogenetic analysis. These strains formed a distinctive cluster in the phylogenetic tree with human and swine HEVs isolated in the USA and human HEVs isolated in Japan. Anti-HEV antibodies were identified via ELISA in 8 of 99 (8.1%) cats, whereas, among 115 cattle and 213 dogs, no HEV-specific antibodies were detected. The conserved RNA-dependent RNA polymerase (RdRp) gene of HEV could be detected via RT-PCR in 8.7% of raw oysters collected from coastal regions in Korea. The HEV RNAs detected in oysters were identified as belonging to subtype 3a. The HEV RNAs in oysters most closely resembled that of the swKOR-2 strain. They also showed a close genetic relationship with the swKOR-1 strain and the swine and human HEVs isolated in the USA. This is the first report describing the detection in oysters of HEV that may have originated from genotype 3 swine HEV in Korea. Pigs and cats infected with HEV, as well as oysters contaminated with HEV, are potential risk factors for HEV transmission to humans.