Epidemiological and clinical study of sporadic acute hepatitis E caused by indigenous strains of hepatitis E virus in Japan compared with acute hepatitis A

Background We compared acute hepatitis E (AH-E) and acute hepatitis A (AH-A) to investigate the epidemiology, clinical features, and prognosis of AH-E caused by an indigenous hepatitis E virus (HEV) in Japan. Methods. We enrolled 58 patients diagnosed with AH-A or AH-E (32 men and 26 women; age, 20-72 years) from December 1997 to October 2002. Phylogenetic analysis of the partial 412-nucleotide sequence of open reading frame (ORF) 2 was performed in patients with AH-E. Results. Regarding the geographic distribution of the HEV genotype, genotype III was principally distributed in Honshu Island, and genotype IV in Hokkaido Island (P = 0.0034). The phylogenetic analysis of the ORF2 region revealed that there were significant geographic differences in the distribution of the HEV strains in Japan, with some strains being widespread and some, localized. In comparison with AH-A patients, those with AH-E were older (56.1 +/- 10.6 vs 45.9 +/- 10.8 years; P = 0.0017). The proportion of males among patients with AH-E was significantly higher (P = 0.0001). Pyrexia was often observed in AH-A, and malaise in AH-E. Laboratory data indicate that AH-E induces a weak immunological reaction, whereas jaundice appears earlier in AH-E than in AH-A. One patient with AH-E died of acute hepatic failure, but none of those with AH-A died during the study period. Conclusions. Our results suggest that there are geographical differences between HEV strains in Japan, and that AH-E is more common in males and older patients than AH-A. Laboratory data indicate a weak immunological reaction and early appearance of jaundice in AH-E.