BACKGROUND Autochthonous hepatitis E occurs sporadically in developed countries. The consumption of undercooked pork containing hepatitis E virus genotype 3 (HEV-3) or 4 (HEV-4) is the major risk factor for infection. The serological diagnostic kits currently used in hospitals sometimes produce false-negative or -positive results. Therefore, detection of both HEV RNA and antibodies to the virus is required for confirmative diagnosis of hepatitis E.

OBJECTIVES We aimed to detect HEV in serum samples from patients with cryptogenic hepatitis and to determine the origin of HEV.

STUDY DESIGN A nested polymerase chain reaction (PCR) method was developed for detection of HEV-3 and HEV-4 in patients with hepatitis. A total of 23 serum samples, deposited in 2006-2012, from patients with acute cryptogenic hepatitis who were serologically negative for hepatitis A, B, C, and E were examined using this method. The amplified PCR products were genetically analyzed.

RESULTS Four HEV-4 isolates were detected from the 23 serum samples. Phylogenetic analysis indicated that three of the four isolates were closely related to HEV-4 isolates found in pigs in Korea and in patients with hepatitis E in Japan.

CONCLUSIONS The newly developed nested PCR method was useful for detection of HEV in patients with cryptogenic hepatitis. The close relationship between the human HEV-4 isolates identified in this study and swine isolates implied that zoonotic transmission of HEV might be a source of infection in patients with hepatitis.