Hepatitis E virus (HEV) is a common cause of acute hepatitis infections. Our previous 3-year study at two large Thai hospitals established an occurrence of 4-5% of HEV infections from swine HEV genotype 3 in suspected acute hepatitis patients, with the high incidence in older adults. This study was a serosurvey to determine the prevalence of HEV infections among Thai adults. We obtained sera from 630 healthy blood donors with a median age of 38 (18-64) years who attended Thai Red Cross transfusion units throughout Thailand. The donors were domiciled in 16 provinces in the northern (n = 159), central (n = 193), northeastern (n = 158), and southern (n = 120) regions. The seroprevalence of IgG antibody to HEV (anti-HEV) was determined by the EUROIMMUN test kit, using indirect enzyme-linked immunosorbent assay (ELISA) based on recombinant antigens derived from ORF2 of HEV genotypes 1 and 3. Demographic data, including information related to HEV infection risk (the number of pigs and the proportion of Muslims in each province), were also obtained. The overall anti-HEV prevalence among Thai adults was 29.7%. The frequencies of anti-HEV found in the northern (28.9%, 95% confidence interval [CI] = 22.4-36.4), northeastern (34.8%, 95% CI = 27.8-42.5), and central (35.8%, 95% CI = 29.3-42.7) regions were similar, whereas the frequency in the southern (14.2%, 95% CI = 9.0-21.5) region, known to have a large Muslim population, was low. An increasing frequency of the specific antibody was observed among the elderly. A low HEV infection rate was associated with an Islamic population where there are low number of pigs and low swine consumption. Furthermore, the higher anti-HEV incidences in the northeastern provinces might relate to the local cultural practice of consuming undercooked pork. Besides the need for an HEV vaccination in the future, there is a requirement for rapid early diagnosis; the undertaking of prevention-management campaigns might also reduce the number of infected patients.
Keywords: Thailand; adult donors; anti-HEV; seroprevalence.