The slaughter of thousands of turkeys is under way today as officials battle to stamp out Britain's first outbreak of the potentially deadly H5N1 strain of bird flu.
Scientists confirmed the avian flu which killed more than 2,000 birds on a Bernard Matthews farm at Holton, near Halesworth in Suffolk, is the highly pathogenic Asian strain.
The Department for Environment, Food and Rural Affairs (Defra) has dramatically increased the area where restrictions are in force in East Anglia to control the H5N1 outbreak.
The Restriction Zone, in which poultry must be kept isolated from wild birds and movements must be licensed, covers 2,090 square kilometres (806 square miles) of east Suffolk and south east Norfolk.
It extends to the A47 just south of Norwich in the north, the A140 in the west, and almost to Felixstowe in the south.
The zone, which was introduced after consultation with ornithologists, is in addition to the 3km protection zone and the 10km surveillance zones already in place.
Around 159,000 birds on the farm where the outbreak was identified are being culled, Defra said.
But Government officials were keen to reassure the public there was no need to panic, as the risk to humans was "negligible".
Turkeys first began falling ill on Tuesday, and by Thursday Defra had been informed and restrictions were in place around the farm itself.
Yesterday, tests at the European Union laboratory in Weybridge, Surrey, confirmed the dangerous form of avian flu on the Suffolk farm.
Deputy Chief Veterinary Officer Fred Landeg said an investigation was under way to discover the source of the outbreak, whether there was another premises infected or if the disease came from wild birds.
"We are not complacent at all and hopefully we will be able to contain it," Mr Landeg said.
"The countryside is not closed, the risks to the public are negligible."
But he urged commercial poultry farmers to step up their biosecurity procedures to prevent spread of the disease.
"The industry must ensure it is trying to carry out the best possible biosecurity," he said.
Former home secretary and MP for Norwich South, Charles Clarke, said the consequences for the local area could be "devastating", although he believed Defra had acted swiftly to contain the outbreak.
"We will have to analyse exactly what happened and the speed with which things took place," he told Sky News.
"But at the moment it seems to me, and I am not an expert, that the action being taken by Defra is very fast, very expeditious and I hope it gets sorted out very quickly."
Asked if it could be devastating for the region given the importance of Bernard Matthews, he said: "It is devastating. He is a major employer here."
He added: "It (Bernard Mathews) has been an important contribution to life in this county so I hope it gets sorted out very quickly."
Defra surveillance of wild bird deaths is ongoing, and members of the public are being asked to report single deaths of ducks, geese and swans, or groups of 10 or more dead birds of any one species in a single area.
Experts are playing down fears that the highly pathogenic bird flu strain could ultimately mutate to a type easily passed between people.
Although 164 people have died of H5N1 since January 2003, mostly in Asia and the Middle East, all have come into direct contact with infected poultry.
At the moment not a single case reported across the globe has been a result of human to human contact.Reuse content