H5N1: The deadly strain of bird flu is here. But we're told: Don't panic

The first major outbreak of bird flu to hit Britain was confirmed yesterday, sparking fears that the virus will spread throughout the country and prompting a cull of 160,000 possibly infected birds.

As vets and scientists tried to trace the source of the country's first infection of the H5N1 strain of the disease, which has killed 164 people in Asia, government scientists sealed off the farm at the centre of the alert.

The emergency measures were introduced after tests by the Veterinary Laboratory Agency confirmed that more than 2,000 birds had been killed by the highly pathogenic Asian strain of the H5N1 virus, which is believed most likely to cause harm to humans. The public was urged not to panic. All the 159,000 turkeys at the farm were due to be culled in an attempt to stop the spread of the disease. The birds were due to be gassed last night and carcasses burnt in an operation taking up to 36 hours.

The health of farm workers and their families was being monitored, entry into the site restricted and essential visitors disinfected. Other poultry farmers within a 10km protection zone were told to keep their stock indoors and out of contact with wild flocks, while pigeon races were banned nationwide. Later Defra widened the restriction zone to cover east Suffolk and south east Norfolk.

David Miliband's Department of the Environment, Food and Rural Affairs (Defra) admitted that "the likelihood of further geographical spread of the virus is high". It is confident that it can stop the disease from moving from the farm to infect other flocks, but believes there are increasing risks of it arriving through migrating birds, the trade in live birds, and the movement of people.

Defra described the risk to the general public as "negligible", saying: "Avian influenza is a disease of birds and, while it can pass very rarely and with difficulty to humans, this requires extremely close contact with infected birds, particularly faeces."

But the outbreak - on a Bernard Matthews farm near Halesworth, in Suffolk, where 2,600 turkeys died last week - casts doubt on the adequacy of defences against the disease, which the Government had said were the best in the world.

A spokesman for Bernard Matthews, Europe's biggest turkey farming company, said no affected bird had entered the food chain and there was no risk to consumers. The Food Standards Agency said properly cooked poultry was still safe to eat.

Dr Fred Landeg, the Deputy Chief Veterinary Officer, told a Defra meeting that all the turkeys had been born at a British hatchery and had never been moved off the farm. The early signs were that this was "a recent introduction of the disease".

There were no plans to vaccinate poultry, Dr Landeg said.