The aim of this study was to analyze the prevalence of infection and genotype of hepatitis E virus (HEV) in people and animals in the northeast of China (Heilongjiang, Jilin and Liaoning provinces). This seroepidemiological study was conducted using enzyme immunoassays and human sera positive for HEV antigen or anti-HEV IgM, and animal sera positive for HEV antigen or with an S/CO <or=10 for anti-HEV were tested for HEV RNA using real-time RT-PCR and nested RT-PCR. In humans, the overall prevalence of anti-HEV IgG was 31.6% (311/985), 28.6% (147/514) and 21.1% (841/3994) in individuals frequent, infrequent, and very rare contact with swine, respectively. The overall prevalence of anti-HEV was 81.6% (1737/2127) in pigs above 3 months of age, 66.4% (1644/2473) in pigs below 3 months of age, 18.7% (301/1612) in cattle and 12.4% (162/1302) in sheep. 1211 samples were tested for HEV RNA using real-time RT-PCR and 71 were positive. 30 of the 71 samples also were positive for HEV RNA using nested RT-PCR. These 30 isolates shared 81.2-100% sequence identity with each other at the nucleotide level and belonged to HEV genotype 4, regardless whether from human or animals. The results indicate that HEV infection is widely spread in the northeast of China. The prevalence of anti-HEV in individuals with frequent contact with pigs was significantly higher than those without and the HEV sequences isolated from such individuals were related more closely to isolates from pigs. These support strongly the hypothesis of a zoonotic origin of hepatitis E.