International collaborative survey on epidemiology of hepatitis E virus in 11 countries.

We conducted seroepidemiological studies on antibody prevalence to hepatitis E virus (HEV) in 5,233 sera from 11 countries to ascertain the present state of HEV infection on a global basis. The prevalence of anti-HEV IgG increased with age in these tested countries, but the rate of antibody positivity was over 20% in the 16-30 year-old group in most of the participating countries, except for Japan, the USA, and Spain. Of patients with acute hepatitis of unknown etiology from Nepal, 56% (14/25) were positive for the IgM class of anti-HEV antibody. In addition, HEV RNAs in the serum from 3 Nepali patients who had the IgM antibody were detected by nested PCR and all of the HEV genes isolated belonged to genotype 1. Our results indicate that HEV is spreading worldwide, not only in developing countries, but also in more industrialized countries than previously thought.