Genotype analysis of hepatitis E virus from sporadic hepatitis E cases in northern China.

Hepatitis E is an important public health problem in many countries. However, there is no definite conclusion about the zoonotic reservoir, transmission patterns and risk factors of hepatitis E in the human population. The aim of this study was to analyze the epidemiological and viral genotype characteristics of hepatitis E cases in northern China. Surveillance was conducted in two hospitals in Liaoning and Hebei province from July 2010 to June 2012. Out of a total of 116 diagnosed patients, 88 (75.9%) were male and 28 (24.1%) were female and most (73%) were in the age group 40-70 years. In both hospitals, cases were diagnosed more frequently in March than in other months. HEV RNA was amplified from 41 patients and characterized by nucleotide sequencing and phylogenetic analysis. Most of the isolates (37 strains, 90.3%) were genotype 4, including subgenotypes 4a, 4b, 4d, 4h, 4i and a new subgenotype. One subgenotype 3a strain was isolated from Baoding, Hebei province. Three genotype 1b strains were found from patients in Jinzhou, Liaoning province. Most of the genotype 4 strains and the genotype 3 strains were phylogenetically related to known swine isolates. In conclusion, the finding that HEV infects mostly middle-aged and elderly men and that the incidence spiked in March may reflect the zoonotic transmission characteristics of HEV infection. Pigs, but not rabbits, were the important reservoirs in this area, because genotype 4 HEV was found to be responsible for the majority hepatitis E cases. However, genotype 1 is still present in northern China. Also, the first isolation of genotype 3 HEV in this area indicates that alternative routes of HEV transmission might exist.