Abstract
A large-scale outbreak of porcine epidemic diarrhea (PED) has been observed in Japan in 2013 after seven years absence. Above 1.2 million pigs have shown typical symptoms such as anorexia, vomiting and watery diarrhea, and approximately 380,000 pigs have died from October 2013 through August 2014. Several virus strains have been successfully isolated from the affected piglets during outbreak of PED. Sequence analyses of the 2013-2014 strains indicated that these were genetically distinct from the strains reported previously in Japan, but were related to the strains recently circulating in the US, Korea and China. It is suggested that PED virus strains detected almost simultaneously in the US, Korea, China and Japan are derived from the common origin. New strains have probably invaded from overseas and rapidly spread throughout Japan since 2013. Further full-genomic analysis of the current field strains in Japan will be required to clarify the global spread and evolutionary dynamics of emerging PEDV strains.
