Further tests on a virus detected in chickens at a farm northeast of Tokyo found that the birds were infected with a bird flu strain that is less virulent than the strain that has ravaged Southeast Asia, the Agricultural Ministry said Friday.
The chickens at the farm in the Ogawa town in Ibaraki prefecture (state), about 100 kilometers (64 miles) northeast of Tokyo, had been infected with the less virulent H5N2 strain of the virus, said Akiko Suzuki, an official at the ministry's bird flu section.
Last week, authorities only determined the virus was from the H5 family and conducted further tests to determine more details of the virus.
Suzuki said officials are preparing to cull 170,000 chickens kept with the infected birds.
Hundreds of thousands of birds at the farm also tested positive for antibodies for the virus, meaning they had been exposed to the virus but survived, but had no viruses.
Agricultural authorities found H5 antibodies at several other farms in Ibaraki in recent weeks, prompting them to cull 180,000 free-range chickens. But this was the first time the bird flu virus, rather than antibodies, were detected in Japan since August, according to media reports.
Ibaraki has prohibited the movement of eggs or chickens within a 5 kilometer (3.1 mile) radius around the farm. The quarantine affects some more than 1 million chickens.
Bird flu hit Japan last year for the first time in decades, with several outbreaks of the deadly H5N1 strain. The country confirmed a human case of bird flu last December but nobody has died. In late October, Japan set up a task force to plan against a possible outbreak of bird flu among humans, reports the AP. I.L.