A retrospective study on imported hepatitis E in Japan.

Hepatitis E virus (HEV), a causative agent of human hepatitis E, is transmitted through an oral-fecal route, often by contaminated drinking water. Serum specimens were collected from 112 non-A, -B, and -C acute hepatitis patients from 1989 to 2004 in Japan. Of these, 24 patients were found to be positive for anti-HEV IgM and diagnosed with acute Hepatitis E. Seventeen of these patients had a clear history of traveling abroad before disease onset and were counted as cases of imported HEV infection. HEV RNA was detected in 16 of these imported cases, and the nucleotide sequences similar to those of HEV detected in India, Bangladesh, and China were identified. By phylogenetic analysis, the remaining imported case appeared to have been imported from India, even though the patient's travel history was uncertain. These results indicated that some sporadic cases of hepatitis E in Japan are caused by imported HEV, and that phylogenetic analyses enable us to identify the country or area where a patient has been infected.