Seroepidemiological study of hepatitis E virus infection in Japan using a newly developed antibody assay

Purpose. A seroepidemiological study of hepatitis E virus (HEV) infection was conducted in Japan, where HEV infection is not considered endemic. Methods. IgG and IgM class antibodies to HEV were measured with a newly developed enzyme-linked immunosorbent assay in which recombinant virus-like particles were used as an antigen. A total of 1253 individuals (401 males and 852 females; age range, 6-89 years) were enrolled from two different areas: area 1 (n = 478), in which hepatitis C was endemic: and area 2 (n = 775), in which it was not endemic. Results. The HEV antibody (IgG class) positive rate was 6.7% in area 1 and 4.6% in area 2. Similarly, the HAV antibody (Ige class) positive rates were 65.3% and 72.3%. The age- and sex-specific prevalence of both HAV and HEV antibodies was quite similar in the two areas, and the HAV antibody positive rate clearly increased with age in both males and females. On the other hand, the HEV antibody positive rate showed a slight tendency to increase with age in males, but not in females. None of the 32 individuals with the HEV antibody who were interviewed had a history of visiting countries in which hepatitis E was endemic. In both areas, the mean age, percentage of males, and HAV antibody positive rate were significantly higher in the group of individuals with the HEV antibody than in the group of those without it, according to conventional statistical analyses. Of the three factors age, male sex, presence of HAV antibody, and the area factor, only male sex was statistically significant (P < 0.001) on multivariate logistic regression analysis. Two (0.2%) of the total of 1253 individuals were positive for the IgM class antibody to HEV. Conclusions. Our results suggest the possibility that HEV infection is circulating in Japan at a low level, HEV infection was associated with male sex, but not with HAV infection.