Best scientific advice must be used to understand bird flu risks

The Government risks not being properly prepared if a future outbreak of avian flu were to result in a human influenza pandemic the Royal Society warned today (6 February 2007).

The Royal Society said that the Government has still not taken onboard the recommendations of last year's joint Royal Society and Academy of Medical Science report on preparing for a potential influenza pandemic. According to the report, "Pandemic influenza: science to policy", the Government is not making the best use of independent scientific advice when making critical decisions on issues such as the stockpiling of antiviral drugs.

Dr John McCauley, a member of the Royal Society/ Academy of Medical Science working group on pandemic influenza, said: "Hopefully this particular outbreak has been contained and it is important to stress that the risk of the virus spreading to humans is minimal. However, should a bird flu virus become able to adapt to humans, it could leave us facing a flu pandemic. There have been three pandemics in the last 100 years, one of which killed 40 million people in 1918. It is important that everything possible is done to ensure that doesn't happen"

The Royal Society and Academy of Medical Sciences report recommended that:

• DEFRA should set up a vaccination committee to advise the department on the development of its vaccination strategies across all animal diseases, including avian influenza.
• The virus must be carefully monitored so we can understand how minor changes or mutations to the virus can potentially affect its ability to spread. As the virus mutates its ability to be transmitted between animals, animals and humans or potentially between humans may also increase.
• A leading influenza specialist should be appointed as a high-level adviser to government ensure that its monitoring and response to such outbreaks is based on the best scientific advice
• The Department of Health and the vaccine industry should continue to evaluate the use of whole virus vaccines and monitor the results of ongoing trials of whole virus vaccines against H5N1
• The Department of Health should revisit it its decision to stockpile only one anti-viral Tamiflu in light of emerging scientific evidence that H5N1 can develop resistance to this drug

reposted from: http://www.royalsoc.ac.uk/news.asp?id=5883
my highlights / emphasis / comments

Health teams in flu pandemic test

It is feared that a flu pandemic could kill 400,000 people in the UK

Hundreds of health officials from across Britain have taken part in an exercise to see how to deal with a flu pandemic.

Officials stayed in a bunker at the Department of Health, in London, as part of the logistical exercise.

The strategic trial is thought to be the biggest emergency planning event since the end of the Cold War.

Officials estimate that a flu pandemic would affect one in four people and cause 400,000 deaths in the UK.

The NHS is ready to implement its well-rehearsed plan Sir Liam Donaldson Chief Medical Officer for England

It is feared that the H5N1 strain of bird flu, which has killed 167 people, mostly in South East Asia, could mutate into a form that would put millions of people at risk worldwide.

At present, this virus cannot pass easily from human to human, and remains essentially a disease of birds.

But in theory if it mixed with a human flu virus it could mutate into a much more dangerous form.

Dummy run

In the trial scenario, the first infected person was a businessman from Surrey who recently returned from South East Asia.

The operation was an attempt to estimate the way in which certain aspects of the country's infrastructure, such as health, transport, education and food distribution would keep working during an outbreak.

Under current planning for an outbreak, schools would be closed in areas suffering an outbreak, to protect children and stem the spread of the disease.

A dedicated "flu line" would field calls from the public, and be used to distribute the stockpiles of Tamiflu antivirals to those who had symptoms of the virus, although there are concerns the "worried well" may attempt to gain the drugs unnecessarily.

Prototype vaccines could be given to health care workers who are most at risk of catching the flu, but there are currently no plans to vaccinate ministers and government officials.

Pressure

Hospitals may be put under extreme pressure - with some A&E units forced to closed, and patients transferred to other hospitals.

Employers might be asked to stagger working hours to prevent overcrowding on public transport in a bid to limit transmission.

People with flu symptoms would be asked to stay at home, but it is not expected the government would step in to cancel sporting events or other mass gatherings.

Sir Liam Donaldson, Chief Medical Officer for England, said: "When a flu pandemic hits the country the top priority for the government is to protect the public.

"The World Health Organization has said that the UK is at the forefront of preparations internationally, but it is always necessary to test our responses and improve them where required.

"This exercise is another part of the continual testing, refining, and developing of our plans.

"The NHS is ready to implement its well-rehearsed plan."

reposted from: http://news.bbc.co.uk/1/hi/uk/6377655.stm
my highlights / emphasis / comments

UK bird flu outbreak - who dunnit?

Exclusive

• 18:00 12 February 2007
• NewScientist.com news service
• Debora MacKenzie

On 3 February 2007, confirmation came that the deadly strain of H5N1 had made it to Europe’s biggest poultry plant, the Bernard Matthews turkey farm in Suffolk, eastern England (see H5N1 bird flu outbreak confirmed on English farm). It was the second confirmed case of this strain of the virus in a European Union state in 2007, following an outbreak in Hungary.

The H5N1 virus is known to have infected 270 people and killed more than 160 worldwide since 2003, most of them in Asia, and over 200 million birds have died from it or been killed to prevent its spread. (Find out more in our Bird Flu special report.)

The H5N1 bird flu was found in a turkey production plant with active biosecurity measures – how did it get in and where did it come from? New Scientist investigates (see graphic, right).

Suspect: East Asia

Evidence: The highly pathogenic H5N1 bird flu that has killed 166 people so far first evolved in poultry in southern China, and it has spread with poultry across the region. It has become widespread in poultry and has caused the most cases so far in people – Indonesia is now hardest hit.

Verdict: Extremely unlikely to have spread directly from here to the UK. The H5N1 circulating in Europe is descended from a strain first isolated in wild birds at Qinghai Lake in central China in 2005. This is genetically distinct from the H5N1 circulating in poultry in the Far East.

Suspect: Siberia

Evidence: Dabbling ducks can carry H5N1 and stay healthy. Many dabbling ducks now wintering in Europe spent the summer nesting in Siberia. Nesting grounds are where birds contract bird flu most often. 20 kilometres from Holton is a nature reserve where wigeons – gregarious dabbling ducks that summer across Siberia – are wintering. Those ducks could well have nested alongside birds now wintering in Hungary. They all could have carried the same virus from Siberia to both England and Hungary, where it circulated at a low level among other birds. Then some local poultry farm just got unlucky.

Further evidence: Recent H5N1 outbreaks in poultry in Krasnodar on the Russian Black Sea coast, and in eastern Turkey (major destinations for the same ducks) plus suspected human cases in nearby Azerbaijan.

Verdict: Likely. How did H5N1 get from wild birds into “closed” turkey barns? A worker could merely have stepped in duck faeces then walked into a barn, say scientists. Turkeys are incredibly sensitive to H5N1.

Suspect: Hungary

Evidence: Hungary had an H5N1 outbreak in geese in Csongrad on 19 January, and the virus is described as genetically very similar. The British outbreak started on 27 January 2007.

Verdict: Just because one happened after the other, it doesn’t mean the first one caused it. Bernard Matthews, the company that owns the British turkey farm, owns a turkey processing plant at Sarvar, Hungary, which sends 38 tonnes of “partly processed” turkey to the British plant weekly. But Sarvar is 260 kilometres from Csongrad making direct spread unlikely. Some Sarvar turkeys were slaughtered at a plant also handling Csongrad birds, so carcasses might have been some cross-contaminated. A smear of turkey on a worker’s shoe could have got it from processing plant to turkey barn.

Suspect: Scotland

Evidence: Britain’s only previous case of H5N1 was a dead whooper swan in a harbour in Cellardyke, Scotland, in March 2006. Could the virus have persisted in British birds? No other birds with H5N1 have been found in Britain, and officials have suggested that the swan was infected in Germany, and died while migrating over Scotland. But questions surround Britain’s wild bird surveillance. Scientists in Sweden find influenza viruses of all types, on average, in 14% of dabblers tested, with higher levels in autumn after nesting season. But last autumn the British testing programme found influenza in a tiny 0.8% of thousands of dabblers tested. This suggests the methodology is missing infected birds, and potentially H5N1. On the other hand, H5N1 is clearly rare; the best way to detect it might be to leave “sentinel” turkeys outdoors.

Verdict: Likely. The same wild British ducks that infected the Scottish swan may have infected the Bernard Matthews turkeys. A worker could merely have stepped in duck faeces then walked into a barn, say scientists.

reposted from: NewScientist
my highlights / emphasis / comments

Indonesia: All domestic chickens, pigeons, and ducks to be culled to halt bird flu

Jakarta, Indonesia, January 28, 2007—A rooster looks on as a man prepares a pit for burning slaughtered birds in Jakarta, Indonesia. The Indonesian government recently declared that all domestic chickens, pigeons, and ducks should be culled to halt the spread of the avian influenza virus.

Jakarta officials estimate the toll of voluntarily slaughtered birds at about a hundred thousand so far, but efforts have been hampered by residents hiding their fowl or bribing health officials to let them keep the birds.

About 164 people worldwide, including 63 Indonesians, have died since 2004 from bird flu. So far the virus that causes the disease, H5N1, has not mutated to allow easy human-to-human transmission. But world health officials fear such a development, which could trigger a deadly global pandemic, is possible. The Indonesian government has said it will soon declare a state of emergency to combat the virus.

reposted from: nationalgeographic.com
my highlights / emphasis / edits

Mass turkey cull to halt bird flu

Tens of thousands of turkeys are being culled at a Suffolk farm as efforts continue to prevent the spread of a mass outbreak of bird flu.

Government vets say 50,000 turkeys have been gassed so far at the Bernard Matthews site near Lowestoft where the H5N1 strain of the virus was found.

reposted from: BBC Last Updated: Sunday, 4 February 2007, 20:24 GMT
my highlights / emphasis / edits

Officials, who said a further 100,000 birds would be killed, denied they had responded slowly to the outbreak.

Sealed lorry loads of carcasses are being taken 200 miles to be destroyed.

Compensation

Government vets said 50,000 turkeys had been gassed at the farm at Holton, about 27km south-west of Lowestoft, by 1300 GMT on Sunday.

The cull is expected to be completed by Monday morning.

Fourteen sealed lorries containing the bird carcasses were travelling to a rendering plant in Cheddleton, Staffordshire, on Sunday evening where they will be destroyed.

The Department for Environment, Food and Rural Affairs (Defra) has confirmed that the Bernard Matthews company will be entitled to compensation for the slaughtered birds.

Q&A: Bird flu Send us your comments

The company could claim under the Animal Health Act 1981 the value of each bird just before slaughter as well as that of any eggs and property removed and destroyed, a spokesman said.

Investigations are continuing into how the disease, identified as the "highly pathogenic" Asian strain of the H5N1 bird flu virus, entered the poultry flock.

Some experts have suggested it might have been spread by wild birds.

The first turkeys died at the site on Tuesday and government vets were called in on Thursday after a vet for the Bernard Matthews company concluded the disease was "unidentifiable".

The authorities have denied their response was slow.

Fred Landeg, the government's deputy chief vet, said that although the company vet was called out on Tuesday, turkeys only began to die in significant numbers two days later, suggesting avian flu might be cause.

Farmer reacts to threat

"The premises were immediately placed under restrictions and an investigation started," he said.

A biosecurity zone has been set up around the farm and poultry owners in the restricted area have been told to keep their flocks isolated from wild birds.

A three-kilometre protection zone and a 10km surveillance zone also remain in place around the farm site.

A much wider restricted zone covering 2,090 sq km is bordered by the A140 to the west and the A47 to the north and almost to Felixstowe in the south.

What each zone means

Health experts have been quick to quell fears the virus found in Suffolk could be passed on to humans.

The avian flu virus has so far killed 164 people worldwide - mainly in south-east Asia - since 2003. So far, all those who contracted the virus had come into close contact with infected birds.

Bird watchers stay vigilant

Health Protection Agency chief executive Professor Pat Troop said the virus "doesn't pass easily from bird to human" and the risk to the general population from the outbreak was "very, very low".

But Health Secretary Patricia Hewitt said the government was taking the possibility of a human flu pandemic in Britain "very seriously".

The Department of Health had taken the advice of scientists and stockpiled enough of the Tamiflu anti-viral drug to cover a quarter of the population, she told ITV1's The Sunday Edition.

But agencies dealing with the Suffolk cull said they were confident it had been contained.

The virus has so far been detected in only one shed out of 22 at the site, and 100 of the 2,000 staff who work at the Holton farm have been given the Tamiflu anti-viral drug.

DEFRA CONTINGENCY PLAN Full document [372KB] Most computers will open PDF documents automatically, but you may need to download Adobe Reader. Download the reader here

A spokesman for the Bernard Matthews company said none of the affected birds had entered the food chain and there was no risk to public health.

Jill Korwin, assistant head of Trading Standards for Suffolk, added: "At the moment we are very encouraged that it has been contained."

But United Nations co-ordinator for bird flu, David Nabarro, has said farmers will have to get used to the presence of the disease in the UK as it is "going to be in bird populations for several years to come".

For more information call the Defra Helpline on 08459 33 55 77

If you have any pictures from the scene you can send them to yourpics@bbc.co.uk or text your pictures to 07725 100 100.

Scene of outbreak All poultry to be culled Visitors disinfected and restricted access 3km Protection Zone Poultry kept indoors and tested 10km Surveillance Zone No movement of poultry to or from area except for slaughter Trains carrying live poultry are prevented from stopping in the protection zone Bird fairs and markets banned Increased surveillance of wetland areas Domestic birds not to share water used by wild birds Footpath restrictions likely only on free-range farms People in towns not affected unless they keep poultry. Restriction Zone Isolation of poultry from wild birds Poultry movements to be licensed Source: Defra Timeline of Bird Flu in UK Quick guide to Bird Flu Wikipedia H5N1 article

World braced for huge surge in bird flu cases

· 160,000 turkeys slaughtered on farm
· Don't panic over food, plead experts
· Concern at delay in informing Defra

Robin McKie and Nick Mathiason
Sunday February 4, 2007
The Observer


All the turkeys on the affected farm near Lowestoft will be culled. Photograph: Chris Young/PA

reposted from: Observer
my highlights / emphasis / edits

The number of cases of the deadly bird flu virus is increasing around the world as scientists struggle to combat the disease that is now threatening to jump species and infect humans. The news comes as Britain confirmed its first ever case of H5N1 in a farm in Suffolk. More than 160,000 birds will now be slaughtered as the country's farming industry goes on high alert for more outbreaks.

As the authorities responded to the outbreak in Suffolk, local residents questioned why it had taken some 48 hours after the first chicks died last Tuesday for the government's Department of Food and Rural Affairs, Defra, to be informed.
But there was also wider concern. Japan and Nigeria have reported a series of cases of the lethal virus, and China, Egypt, Russia, South Korea and Vietnam have also revealed outbreaks in birds and in humans in the past two months. Indonesia began a mass bird cull in the capital city of Jakarta last Wednesday. At least 164 people are now known to have been killed by the disease across the globe.

The rapid spread of avian flu can be traced to the fact that the H5N1 virus is mutating as it spreads through birds and a variety of mammals including cats, tigers and pigs, said Robert Webster, a researcher at St Jude Children's Research Hospital, in Memphis, Tennessee.

Last night British health officials insisted the risk to the public was still negligible. It set in motion a series of emergency measures aimed at halting the spread of the disease among poultry in Britain. All the turkeys on the affected farm at Holton near Lowestoft, the largest poultry centre run by the breeder Bernard Matthews, are now being culled. Yesterday, piles of slaughtered birds were being scooped into open tractor trailers before being removed for incineration.

An exclusion zone of three-kilometres (nearly two miles) has been set up around the farm. All poultry in the area are to be kept indoors and tested for the H5N1 virus. A further 10km zone has been established in which all movements of poultry are banned, and last night another 2,090sq km restriction zone was created to isolate poultry from wild birds. Other measures will include a ban on bird shows, poultry markets and pigeon racing. This follows a decision by Defra to revoke the national general licence on bird gatherings.

Last night, the National Farmers' Union president, Peter Kendall, said his organisation had warned members to be vigilant. A spokesman for Matthews said his organisation could confirm there had been a case of H5N1 avian influenza at its Holton site. But he added: 'It is important to stress that there is no risk to consumers.'

Dr Andrew Landeg, the government's deputy chief veterinary officer, revealed he had called in ornithologists in a bid to understand how wild fowl - now thought to be the most likely source of the Suffolk outbreak - might have carried the virus into one of the 22 turkey breeding sheds at the farm. Officials also needed to know what other areas of the country might now be at risk of outbreaks.

Last night, it was revealed that Defra had identified several areas in Britain considered to be at particular risk of picking up H5N1 from infected wild fowl. The farm at Horton was one of them.

Avian flu expert Dr Colin Butter of the Institute of Animal Health said it was now crucial that veterinary scientists discover whether the farm was the first place this strain of flu had emerged. It could be that the outbreak was an 'unhappy chance event', or it could indicate a significant level of the disease in wild birds indigenous to the UK, which in turn would make the virus harder to stamp out. Exclusion zones and culling would not be sufficient to contain the virus, Butter added.

However, Landeg yesterday ruled out the alternative - the introduction of vaccinations for poultry, a measure already introduced in Holland - as being ineffective.

As a result, farmers with free-range flocks may face serious threats to their livelihood. However, one organic poultry producer said moves to house birds permanently indoors would be counter-productive. 'My birds are resistant to the range of diseases that affect conventional flocks because their immune systems have been boosted through living outdoors. I accept that as a new strain of bird flu, special measures may be required in the short-term, but these should not be at the expense of the principles of good husbandry.'

However, Landeg yesterday insisted that the disease could be contained. 'There's a good hope, if this is not the first case, we will be able to contain this disease.'

It was revealed last night that five people in Indonesia have died from the virus since the beginning of the year while Japan yesterday confirmed its fourth outbreak of H5N1 bird flu this year and Thailand has reported three outbreaks during the past month.

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Bird flu in Sussex - Experts play down risk to humans

Last Updated: Saturday, 3 February 2007, 13:34 GMT

Experts play down risk to humans

Bird flu cannot pass easily between humans Experts have stressed the outbreak of bird flu at a farm in Suffolk poses no immediate risk to human health. The outbreak has been confirmed as the H5N1 strain of the virus which has infected 270 people, and killed 164 - most in south east Asia - since 2003. However, the virus cannot easily pass from human to human at present. reposted from: BBC my highlights / emphasis / edits So far, all those who have been infected have been poultry workers who have come into intimate contact with infected birds. There is no immediate public health risk Dr Colin Butter Institute of Animal Health Experts warn that if the virus acquires the ability to pass from human to human, then it will pose a potential threat to millions across the globe. Health chiefs in the UK have warned that if such a modified strain does emerge then tens of thousands of people could die in Britain alone. However, at present H5N1 remains overwhelmingly a disease of birds, and not humans. So at present the threat to human health from the outbreak in Suffolk is minimal - particularly as it appears to have been rapidly contained. Asia is key Dr Colin Butter, a bird flu expert at the Institute of Animal Health, said: "This outbreak is no risk to the general public and will be controlled by culling. It is exceedingly unlikely that any human is going to get sick as a result of H5N1 in one turkey farm in Britain at this time Dr David Nabarro United Nations "The risk to public health is from a human pandemic which is not likely to originate in Europe. "A pandemic of this type, if it does happen, is likely to occur in an area where people live side by side with birds, like in East Asia. "So there is no immediate public health risk, but this is clearly something we need to get under control." Dr David Nabarro, bird flu coordinator for the United Nations, also stressed that H5N1 posed little threat to humans. He said: "It is exceedingly unlikely that any human is going to get sick as a result of H5N1 in one turkey farm in Britain at this time. "The numbers of human cases are very, very small indeed, even though the virus has been moving through poultry in at least 50 countries in the last year, and led to millions of birds dying. "This is really not a human disease, it is a poultry disease." Farm workers Peter Kendall, president of the National Farmers' Union, said the workers on the Suffolk farm were also unlikely to be at risk. He said poultry workers in south east Asia effectively lived with their birds, and had far closer contact than any of their counterparts in the UK. "On a modern poultry farm a lot of the feeding is done mechanically, and the involvement of the workers with the poultry is really minimalised." Dr Maria Zambon, from the Health Protection Agency, said farm workers who had come into contact with infected birds, and those involved in the culling process would be offered the anti-viral drug tamiflu as a precaution. She stressed that nobody had developed symptoms of bird flu following similar outbreaks among farm birds in continental Europe. David Catlow, president of the British Veterinary Association, said the Department of Environment, Food and Rural Affairs had acted quickly to contain and isolate the outbreak. He stressed that the public were safe to continue eating poultry. Virus mix The H5N1 virus is most likely to acquire the ability to pass easily from human to human if it mixes with a standard flu virus, and swaps genetic material. This could happen if H5N1 infects a human - or other animal - which is already infected with standard flu. To minimise the risk of this happening in the UK, the Department of Health recently announced that it would offer seasonal flu vaccine to poultry workers across England. The theory is that if poultry workers are kept free of normal flu, then even in the highly unlikely event that they were infected with H5N1, the bird flu virus would not come into contact with its cousin.

H5N1 bird flu outbreak confirmed on English farm

• 13:25 03 February 2007
• NewScientist.com news service
• New Scientist, Reuters and AFP

An outbreak of bird flu on a farm run by Europe's biggest turkey manufacturer Bernard Matthews is the highly pathogenic H5N1 version of the virus which can kill humans, the European Commission said on Saturday.

Government veterinary experts were called to the farm near Lowestoft in eastern England late on Thursday after the death of 2500 birds. The UK government is enforcing EU-agreed controls to contain the outbreak, which involves setting up a protection zone with a radius of 3 kilometres (2 miles) and a surveillance zone of 10 km around the infected farm.

reposted from: New Scientist
my highlights / emphasis / edits

It is the second confirmed case of H5N1 in the 27-country European Union in 2007, following one in Hungary.

The farm has 160,000 turkeys, but only one of the 22 sheds that house the birds has so far been affected by the outbreak. Strict movement controls are in place, poultry must be kept indoors, bird shows and pigeon racing are prohibited, and on-farm biosecurity measures will be strengthened.

The H5N1 virus is known to have infected 270 people and killed at least 164 worldwide since 2003, most of them in Asia, and over 200 million birds have died from it or have been killed to prevent its spread. (Find out more in our Bird Flu special report.)

Surprising timing

Avian flu expert Colin Butter, at the UK's Institute of Animal Health, said: "This news is a bit surprising because it's not the time of year when we have a lot of bird migration. If it was going to happen we would expect it to happen in spring, not the middle of winter."

He said it is now crucial to find out if this is the only outbreak, or whether it has spread from another, as-yet-undiscovered outbreak. "If this is a secondary case it is much more serious. If this is the first case, and we can stamp it out, the outbreak will be controlled."

John Oxford, a virologist at London's Queen Mary's School of Medicine, told the BBC he was confident that the outbreak could be contained: "I don't think it has made any difference to the threat to the human population."

Wild swan

The highly pathogenic strain of H5N1 bird flu was found before in the UK, when a wild swan was discovered dead in Scotland in March 2006 (see UK's first case of H5N1 bird flu confirmed). It was thought to have caught the disease elsewhere, died at sea and been washed ashore.

In May 2006, 50,000 chickens at three farms in Norfolk, also in eastern England and home to some of Europe's biggest poultry farms, were culled after the H7N3 strain was detected. Farming leaders said those two scares cost the UK poultry industry 58 million pounds ($115 million) in 2006.

Peter Kendall, president of the National Farmers' Union, urged consumers not to stop buying poultry because of the outbreak: "We're encouraging all farmers to be incredibly vigilant, and look at their flocks carefully. We do need to reassure consumers, however, that this is not an issue about safety of poultry."

Bernard Matthews said in a statement: "There has been a case of H5N1 avian influenza at the Holton site, but it is important to stress that none of the affected birds have entered the food chain."

Bird Flu - Learn more about the flu pandemic that could kill millions in our continually updated special report.

Tests show bird flu is H5N1 virus in Norfolk

Last Updated: Saturday, 3 February 2007, 16:11 GMT

Tests show bird flu is H5N1 virus

People at the farm in Suffolk are having to wear protective clothing

The avian flu which killed 2,600 turkeys at a Suffolk farm has been confirmed as the H5N1 virus.

That strain can be fatal if it is passed on to humans but experts said the outbreak was being contained and posed little danger to people.

The Department for Environment, Food and Rural Affairs and the European Commission carried out virus tests at laboratories in Weybridge, Surrey.

The 159,000 other turkeys on the farm will now have to be slaughtered.

A three-kilometre protection zone and a 10km surveillance zone will be set up around Holton, which is approximately 27km south-west of Lowestoft.

In pics: containment operation Measures when bird flu hits Q&A: Bird flu

A Defra statement said further tests to characterise the virus were under way in order to ascertain whether or not it is the Asian strain.

It is the first case on a UK commercial farm of infection with the H5N1 strain, which has killed 164 people worldwide - mainly in south-east Asia - since 2003.

However, the virus cannot pass from human to human at present.

So far, all those who have been infected worldwide have come into intimate contact with infected birds.

Vaccinations

Fred Landeg, Britain's Deputy Chief Veterinary Officer, said an investigation was under way but the most likely source of the outbreak was wild birds.

He told BBC News that vaccinations for poultry were not currently being considered.

"There are a number of problems with vaccination in that it takes about three weeks to get immunity."

DEFRA CONTINGENCY PLAN Full document [372KB] Most computers will open PDF documents automatically, but you may need to download Adobe Reader. Download the reader here

Mr Landeg said the turkeys at the farm had been too young to enter the food chain and no birds or produce had moved off the site.

Dr Maria Zambon, from the Health Protection Agency, said farm workers who had come into contact with infected birds, and those involved in the culling process, would be offered the anti-viral drug tamiflu as a precaution.

She stressed that nobody had developed symptoms of bird flu following similar outbreaks among farm birds in continental Europe.

Vets were called to the Bernard Matthews farm on Thursday night.

The company said it was confident the outbreak had been contained and there was no risk to consumers.

How bird flu became global

National Farmers Union president Peter Kendall told BBC News 24 the priority would be eradicating the outbreak.

"[We will be] making sure we get the message across about how well this will be managed and controlled.

"We're encouraging all farmers to be incredibly vigilant, look at their flocks carefully and we do need to reassure consumers that this is not an issue about the safety of poultry - it's completely safe to eat."

Defra has revoked the national general licence on bird gatherings and bird shows and pigeon racing will not be permitted.

Detergent

Professor John Oxford, a virologist at the London Queen Mary's School of Medicine and Dentistry, said he was confident the outbreak could be contained.

He said: "I don't think it has made any difference as a threat to the human population. The most likely explanation is that a small bird has come in through a ventilation shaft.

"One good thing about this virus is that it's easily destroyed. You can kill it with a bit of detergent."

Dr Oxford also said that while four strains of the H5N1 virus have been identified so far, all are deadly to birds and show potential of being harmful to humans.

He said that identifying the particular strain found in Suffolk will help scientists work out how the disease is moving around the world.

HAVE YOUR SAY The people most at risk are farmers and their families Andrew Olgado, London Send us your experiences Community in shock

In May last year, more than 50,000 chickens were culled after an outbreak of the H7 bird flu in farms in the neighbouring county of Norfolk.

One member of staff at the farm contracted the disease and was treated for an eye infection.

In March 2006, a wild swan found dead in Cellardyke, Fife, was found to have the H5N1 strain of the virus.

For more information call the Defra Helpline on 08459 33 55 77

WHEN BIRD FLU HITS THE UK 1: Scene of outbreak All poultry to be culled Visitors disinfected and restricted access 2: 3km Protection Zone Poultry kept indoors and tested 3: 10km Surveillance Zone No movement of poultry to or from area except for slaughter Rail transport restricted to non-stopping movements Bird fairs and markets banned Increased surveillance of wetland areas Domestic birds not to share water used by wild birds Footpath restrictions likely only on free-range farms People in towns not affected unless they keep poultry. Source: Defra