The bird flu virus that has led to the deaths of tens of thousands of chickens in Japan and Vietnam is closely related to the one discovered at a goose farm in China's Guangdong Province in 1996, Japanese researchers said Thursday.
The virus found in China is called Gd96 and gave rise to the H5N1 strain, the researchers said. The H5N1 virus led to the outbreak of bird flu in Honk Kong in 1997 that killed six people.
The viral strain found recently in Yamaguchi Prefecture is also H5N1.
The researchers believe it is highly likely that the current outbreak originated in China.
The National Institute of Animal Health in Japan compared genes isolated from samples taken from infected chickens in Yamaguchi with genes of other H5N1 viruses found in other countries.
The researchers found the base sequence of the HA gene, which determines virus types, was 97 percent identical with the base sequence of the virus that caused the death of a man in Hong Kong in February 2003.
The U.S. Centers for Disease Control and Prevention found that the HA strain of the virus found last year in Honk Kong is closely related to the Gd96 virus.
The HA gene of the virus in Japan is 97 percent similar to the gene of the virus now common in Vietnam, the researchers said.
The bird flu viruses in Japan and Vietnam are not exactly the same, but both their genes have the Gd96 genetic lineage, they said.
In Hong Kong, the Gd96 virus was continually found in ducks and geese exported from China since 1997.
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