LONDON -- British authorities confirmed yesterday that an outbreak of bird flu discovered among turkeys at a poultry farm in eastern Britain had been caused by the deadly A(H5N1) strain, which has killed humans in other parts of the world.
The disease has killed 2,500 turkeys near Lowestoft since Thursday, making it the biggest outbreak of the strain reported in Britain since concern about its global spread began to take root in 2003.
An additional 160,000 birds will be culled to prevent the disease from spreading to other locations, government officials said.
The prospect of a mass slaughter recalled Britain's battle with foot-and-mouth disease in 2001, when nearly 4 million animals, mainly sheep, pigs and cows, were killed and then burned on makeshift pyres.
The Department for Environment, Food and Rural Affairs said in a statement that veterinary authorities had imposed restrictions in areas within a six-mile radius of the infected farm in eastern England, owned by the Bernard Matthews company, one of Europe's biggest poultry businesses.
The statement also said that all bird shows and pigeon racing had been banned while scientists tried to establish more detail about the virus and the level of risk it presented to humans. The department did not say what had caused the outbreak.
Fred Landeg, a senior government veterinarian, said there was no public health concern.
"Avian influenza is a disease of birds," he said, "and whilst it can pass very rarely and with difficulty to humans, this requires extremely close contact with infected birds, particularly feces."
The disease is commonly transmitted to farmed birds by migrating birds carrying the infection.
But since 2003, 164 people, most of them in Asia, have died of the disease, and authorities worry that the virus could become more easily transmissible among humans and create a global pandemic.
About 200 million birds have either died or been killed in the same period.
A spokeswoman for the Department of Environment, Food and Rural Affairs said the slaughter and disposal of birds at the Lowestoft farm could take two to 10 days. She said the Bernard Matthews farm was currently "biosecure."
Britain's last brush with the virus was last April, when a dead swan that washed up in Scotland tested positive for the A(H5N1) strain. Government scientists said it had probably carried the infection from Germany and posed no threat to humans.
Later that month, chickens in another part of eastern England - a center of poultry farming - died of a different strain of avian influenza, H7, which can cause mild symptoms in humans.
At that time, a poultry farm worker fell ill with conjunctivitis, which was blamed on the virus.
Fatalities from the A(H5N1) virus that occurred closest to Britain were reported 13 months ago, when two people died in Turkey before the disease began to spread through Western Europe, including France, Germany and Italy.
A statement from the Bernard Matthews company said, "It is important to stress that none of the affected birds have entered the food chain and there is no risk to consumers."