Hepatitis E virus (HEV), the causative agent of hepatitis E, is
an important human pathogen (4 ). The genome of HEV is
approximately 7.2 kb in size and contains three open reading
frames (ORF1, ORF2, and ORF3) (18 ). Although only one serotype
has been recognized, extensive genomic diversity has been noted
among HEV isolates, and HEV sequences have tentatively been
classified into four genotypes (genotypes 1 to 4) (20 ).
Transmission of HEV occurs primarily by the fecal-oral route
through contaminated water supplies in developing countries (18
). In addition, increasing evidence has indicated that hepatitis
E is a zoonosis (4 ). It has recently been suggested that
zoonotic food-borne transmission of HEV from domestic pigs, wild
boars, or wild deer to humans plays an important role in the
occurrence of cryptic hepatitis E in Japan, where people have
distinctive habits of ingesting raw fish (sushi or sashimi) and,
less frequently, uncooked or undercooked meat (including the
liver and colon or intestine of anima