Clinical and molecular analyses of sporadic acute hepatitis A and E and the specific viral genotypes isolated in Iwate and three neighboring prefectures in the northern part of Honshu, Japan, between 2004 and 2013

Aim To examine the prevalence and characteristics of hepatitis A virus (HAV) and hepatitis E virus (HEV) infections in the northern part of Honshu, Japan, during the last decade. Methods Using the registration system of a prospective cohort study for acute liver injury (ALI) in Iwate and three neighboring prefectures, we examined the prevalence of sporadic acute hepatitis (AH) with HAV (AH-A) and HEV (AH-E) and the distribution of viral genotypes in 487 patients diagnosed with ALI between 2004 and 2013. Results Among all 487 patients, 135 (28%) had ALI with viral infection. In the cases with viral ALI, the prevalence of hepatitis B virus-related AH was highest (55.6%). AH-E was seen in 23 patients (17.0%) and its prevalence was higher than that of AH-A (10 patients, 7.4%). There were no appreciable differences in the prevalence of AH-A and AH-E between 2004–2008 and 2009–2013. However, subgenotype IIIA HAV homologous to Korean strains has recently emerged, and the number of AH-E cases seems to be increasing. HEV genotype 3 was predominant throughout the observation period, but HEV genotype 4 was found in three patients after 2010. The transmission routes of HAV and HEV infections were unknown in approximately 60% of the patients. Conclusion In the northern part of Honshu, Japan, HEV has been more frequently implicated in the development of AH than HAV, and HEV genotype 4 has been recently increasing. To provide an effective prophylactic management for HAV and HEV infections, further clarification of the transmission routes is needed.