Migrating birds raise fears of new flu outbreak

Japan's third case in three weeks of avian flu infecting chicken farms has heightened concerns about the risk of a major outbreak of the disease caused by migrating birds from the north Asian mainland. The Agriculture Ministry confirmed last week the presence of the H5 bird flu virus at an egg farm near Takahashi city, about 310km southeast of Tokyo.

Ministry scientists were still working to establish if the Takahashi virus was the same H5N1 strain, potentially deadly to humans, as found in two earlier outbreaks this month on farms in Miyazaki prefecture.

The virus in both Miyazaki cases is suspected of being the Qinghai Lake sub-strain, first found in wild birds in western China, that has spread over the past 18 months to the Middle East and several eastern European countries.

Migratory birds are believed to have been at least one form of transmission for the Qinghai Lake strain, which - although Japanese poultry and egg farmers are advised to keep their birds in sheds or under netting - is thought to be the most likely avenue of infection in the Japanese cases.

That assumption has been strengthened by the pattern of infection - the Miyazaki outbreaks on Kyushu were 60km apart and Takahashi is about 300km to the northeast on the main Japanese island, Honshu.

"In all three cases, experts have said the chickens probably got infected from migratory birds," Agriculture Minister Toshikatsu Matsuoka said.

However, an official told The Australian yesterday that the ministry had not been able so far to identify a common source of infection. Alhough it still spreads with difficulty to humans from birds, particularly chickens, H5N1 has so far infected 267 people and 163 have died, mainly in China, Thailand, Indonesia and Vietnam.

Eighteen other farms carrying 950,000 chickens within 10km of the infected farm have been isolated, and road disinfection stations are being set up.

The Australian