An outbreak of bird flu on a Suffolk farm is the deadly H5N1 form of the virus, Defra confirmed today, while the government warned that the disease may have already spread.
Fred Landeg, the acting chief veterinary officer, confirmed the strain at Redgrave Park farm in Suffolk, which is potentially dangerous to humans and has swept across Asia, Europe and Africa since 2003.
Landeg said the source of the virus was yet to be determined, but confirmed it was closely related to that found in outbreaks seen this summer in the Czech Republic and Germany.
"The initial sequence data suggests that it's closely related to outbreaks in the Czech Republic and Germany, which does suggest a possible wild bird source," he said. "However, at this stage all potential sources of the origin will be investigated."
The environment minister, Hillary Benn, briefed MPs on the outbreak this afternoon, warning them more cases could be discovered in the area.
He said: "There also remains the chance that there may be further undisclosed disease in this area, which has a high density of poultry."
The virus has not been found in any wild birds already sampled.
The last UK case of H5N1 was in February this year, when the disease forced the cull of 160,000 turkeys at the Bernard Matthews turkey farm in Suffolk.
Asked if this virus was related to the February outbreak, Landeg said: "We don't know that yet. We are carrying out detailed investigations with an open mind."
It is the fourth UK case of avian influenza this year. The H5N1 virus has also been found this year in the Czech Republic, Hungary, France and Germany.
A cull of all 5,000 poultry at the infected farm has already begun. A 3km protection zone and 10km surveillance zone were set up yesterday around the farm near Diss, on the Norfolk-Suffolk border.
All free-range birds for meat and eggs in Suffolk and part of Norfolk must be locked indoors to protect them from the spread of the virus.
Hobby farmers with backyard flocks are also being visited by local animal health officers who are urging them to keep birds inside.
The most recent H5N1 incident in Europe was near Munich in September. More than 300,000 ducks were slaughtered at poultry farms after the disease was found in frozen produce.
Bird viruses do not usually infect humans but some people who have been in close contact with infected birds have died. Scientists are worried that avian flu will mutate and spread from person to person, infecting larger numbers of people.
But Landeg said people should not be worried about contracting the human form of the virus.
He said: "This particular strain of virus has on rare occasions passed to human beings, particularly in the Far East, where poultry workers have had very close contact with sick and diseased birds.
"The general public needn't worry about contact with the birds. Spread to humans is not very common and no human has contracted the disease in Western Europe.
"The Health Protection Authority are making sure workers at the infected farm have proper preventative treatment."
The National Farmers' Union president, Peter Kendall, said: "This is another huge blow to the farming industry, which is still dealing with the effects of bluetongue and foot and mouth.
"But it is important to remember avian influenza is a disease of birds. There is no reason for public concern."
Landeg said the minimum time period for restrictions in the infected zone will be 30 days after slaughter, and all other restrictions will be continually reviewed.
Responding to farmers' concerns he said: "Outside of the restricted zone poultry farms will be able to trade freely within Europe. Within the restricted zone there is a complex series of measures which will allow some trade to continue under certain conditions."
The Food Standards Agency has urged people to continue eating eggs and poultry meat, saying they remain safe as long as they are properly cooked.
Geoffrey Buchanan, the operations director of Redgrave Poultry, said the disease was discovered when staff noticed an increased mortality rate at the farm early on Sunday.
He said: "Sixty turkeys out of a flock of 1,000 from one house on the site were found dead. The site was immediately isolated and additional biosecurity measures imposed."
Buchanan said no infected birds from the farm had entered the food chain. "The GA Topham farm is being operated by Redgrave Poultry under the direct guidance of Defra, which is culling the birds on farm as soon as is practically possible with guidance from all the government agencies involved.
"GA Topham is a seasonal farm, preparing birds for Christmas. As such, no birds from the farm have been slaughtered for food or sent to customers.
"All suppliers, farms, contractors and staff have been contacted with as much information as is available and with immediate effect all gates have been locked, and increased biosecurity measures put in place."
The infected farm also has more than 1,000 ducks and 500 geese. Suffolk county council officers are carrying out the cull on behalf of Defra.
Ian Jones, the director of research at the school of animal and microbial sciences at the University of Reading, said: "Another outbreak was to be expected at some time. But the source will be interesting, and may be suggested when the sequence is confirmed.
"It is a bit early for migratory birds, but this is an option assuming the turkeys were outside. It is regrettable ahead of Christmas but there is no reason it should not be contained at this stage."
The Royal Society for the Protection of Birds warned against assumptions that wild birds were to blame for the latest outbreak of the disease.
The RSPB conservation director, Mark Avery, said: "If migrating wild birds were carrying bird flu, their corpses would have been found north and east of the UK, the routes that migrating wildfowl take.
"But there have been no recent reports of wild birds dying of bird flu in the countries on their migration routes.
"Jumping to conclusions over the source of bird flu could blind us to courses of action that should be taken. We can't rule out wild birds as carriers but we're not even close to knowing that claim is true."
Today, Waitrose confirmed the farm was due to supply the company with free-range Christmas poultry.
This is the high season for poultry breeders who would expect to sell more than 20 million birds. Sales of some turkey products declined significantly after the last outbreak of H5 bird flu and are believed to have not fully recovered.
Following the Defra announcement, the environment minister, Hillary Benn, updated MPs on the outbreak.
Benn stressed that avian flu was primarily a bird disease and that there was no risk to humans from eating properly cooked poultry and eggs.
He said a full investigation had started into the origins of the outbreak and the risk of it spreading, but he refused to speculate on the source.
Benn faced a challenge from the shadow environment secretary, Peter Ainsworth, who accused the government of financial mismanagement.
Ainsworth said the outbreak arose from circumstances "beyond the government's control," but accused Benn of forcing councils to cut their animal health budgets by 12% this year, despite the series of farming disease crises.
He said that while £9.7m was promised to councils for dealing with animal disease outbreaks, only £8.5m was allocated "because of Defra's financial mismanagement".
Ainsworth said: "They have now been told to cut their animal health budgets by 12% in the last five months of this year. This is very difficult to understand in the current environment."