| [ Summary ] |
The hepatitis E cases seen in Japan are mostly caused by domestic infection sources, from Japan-indigenous strains of hepatitis E viruses (HEV), rather than from so-called “imported infection”. These sources include zoonotic transmission from swine, deer, wild boar e.t.c. to human beings. This is notable because human to human transmission is very rare (none except for transfusion-transmitted cases). Genotype 3 and 4 strains are autochthonous, with different geographical distributions. The former is prevalent in areas south to the Tsugaru Strait ; the latter in Hokkaido. Molecular clock analysis suggests both strains entered Japan around 1900, but nobody knows definitely where they came from. -- I would gingerly propose my little ideas. |