A novel subgenotype 3a hepatitis E virus isolated from pigs in China

Hepatitis E virus (HEV) infection is an emerging disease with zoonotic transmission that represents a serious public health concern, especially in developing countries. Here we characterize a novel HEV strain CCST-517, which possesses a complete genome sequence of 7284 bp with typical HEV genome organization including 5' and 3' non-coding regions and three open reading frames. The sequence identities of CCST-517 with known HEV genotype 1, 2, 3, and 4 were 73.4-73.7, 73.2, 80.4-90.4, and 75.1-75.7%, respectively. Phylogenetic analysis clustered CCST-517 to the clade of HEV genotype 3a, together with the Japanese human HEV isolate (HE-JA10) and United States human HEV isolate (HEV-US2). Similarity plot analysis indicated that the fragment extending from 4500 to 5500 nt included evidence of one intra-genotype recombination event in the genome sequence of the CCST-517 strain. To our knowledge, this is the first report of HEV genotype 3a with its complete genome sequence revealed in China. Our findings revealed a close phylogenetic relationship of CCST-517 to human HEV-US2 and HE-JA10, implying cross-species transmission of HEV between pigs and humans.