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 w as conducted in Japan, where HEV infection is not considered endemic. Metho ds. IgG and IgM class antibodies to HEV were measured with a newly develope d enzyme-linked immunosorbent assay in which recombinant virus-like particl es 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: are a 1 (n = 478), in which hepatitis C was endemic: and area 2 (n = 775), in w hich it was not endemic. Results. The HEV antibody (IgG class) positive rat e was 6.7% in area 1 and 4.6% in area 2. Similarly, the HAV antibody (Ige c lass) positive rates were 65.3% and 72.3%. The age- and sex-specific preval ence 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 an d females. On the other hand, the HEV antibody positive rate showed a sligh t tendency to increase with age in males, but not in females. None of the 3 2 individuals with the HEV antibody who were interviewed had a history of v isiting countries in which hepatitis E was endemic. In both areas, the mean age, percentage of males, and HAV antibody positive rate were significantl y higher in the group of individuals with the HEV antibody than in the grou p of those without it, according to conventional statistical analyses. Of t he three factors age, male sex, presence of HAV antibody, and the area fact or, 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 s uggest the possibility that HEV infection is circulating in Japan at a low level, HEV infection was associated with male sex, but not with HAV infecti on.