Dead swans found recently in northeast Japan carried the deadly H5N1 strain of avian influenza, the government said on Tuesday.
One dying and three dead swans were discovered April 21 near Lake Towada – a popular tourist spot – in Akita prefecture. Officials had determined earlier that they were infected with the bird flu virus, but further testing by the National Institute of Animal Health confirmed the strain involved.
The incident is Japan’s first outbreak of H5N1 since March 2007, when researchers found the virus in an eagle on the southern island of Kyushu.
Authorities in Akita prefecture plan to spend Wednesday and Thursday inspecting 15 farms within a 30-kilometre radius of where the swans were discovered.
They have also issued a warning to local farmers to keep wild birds from entering their property and to immediately report chickens showing abnormal symptoms. Neighbouring Aomori prefecture has released a similar directive to its residents.
Highly pathogenic, H5N1 has killed tens of millions of birds since the first cases were reported in Hong Kong in 1997.
The virus remains hard for people to catch, but scientists worry it could mutate into a form that spreads more easily between humans, with the potential to kill millions worldwide.
At least 240 people have died from bird flu since 2003, according to the World Health Organisation. Most human cases so far have been linked to contact with infected poultry.
Tuesday’s announcement coincides with a bird flu outbreak this month in South Korea, where millions of birds have been slaughtered to contain the disease.
There had been growing concerns that the virus could jump from South Korea into Japan. It is unclear, however, where the swans in Akita were infected.
Migratory swans typically fly to Japan from Siberia, Russia in the fall and then return north in the spring, according to Kyodo News agency.