Sporadic acute hepatitis E occurred constantly during the last decade in northeast Japan.

Background: Recent studies have shown that indigenous hepatitis E virus (HEV) strains cause hepatitis E in industrialized countries. We aimed to clarify the characteristics of HEV infection in sporadic hepatitis patients during the last decade in Miyagi, northeast Japan.

Methods: We analyzed 94 serum samples obtained from acute or fulminant hepatitis patients of non-A, non-B, and non-C etiology between 1999 and 2008. Antibody to HEV (anti-HEV) was assayed, and patients who were positive for IgM- and/or IgA-class anti-HEV were diagnosed with hepatitis E. HEV RNA was tested in these patients, and phylogenetic analysis was performed. The occurrence of hepatitis E was compared with that of hepatitis A.

Results: Eight acute hepatitis patients (8.5%) were diagnosed with hepatitis E, and HEV RNA was detectable in seven patients. Five isolates of HEV were segregated into genotype 3 and the remaining two isolates into genotype 4. The year of the occurrence of hepatitis E was distributed almost equally from 1999 to 2008, whereas the cases of acute hepatitis A (n = 16) have decreased markedly in the last several years. In 2004-2008, the occurrence of hepatitis E was greater than that of hepatitis A (five cases vs. one case). As for seasonality, hepatitis E occurred more frequently from September to December than hepatitis A (five cases vs. four cases), although less frequently from January to April (one case vs. seven cases).

Conclusion: The occurrence of hepatitis E has not decreased during the last decade in northeast Japan, in contrast to hepatitis A.