A national research institute investigated the virus genes in detail for avian influenza that occurred at an unusual pace in domestic poultry farms this season, and found that there were two strains.
In Japan, "H5N8 type" bird flu has occurred in 51 poultry farms in 17 prefectures since November last year, and the number of chickens slaughtered has reached a record high of 9.7 million.
The National Agriculture and Food Research Organization analyzed the genetic information of 49 cases of viruses detected in poultry farms and investigated them in detail.
As a result, 38 cases detected in poultry farms in 17 prefectures since November last year are viruses of a strain that spread in Europe from adulthood to last year. Eleven cases detected in poultry farms and other places in Japan were found to have been a strain of virus reported in Russia and Europe this season.
Two strains of the virus have also been found in wild birds in the country.
Yuko Uchida, unit manager of the National Institute of Animal Health's Animal Health Research Division, said, "It is possible that a new strain of virus was introduced into the country in the middle of this season, leading to the spread of damage. Therefore, I would like you to continue to be vigilant at poultry farms. "