Deadly strain of Asian bird flu arrives on Europe's doorstep

British scientists confirmed yesterday that an outbreak of bird flu on a poultry farm in Turkey was caused by the deadly H5N1 strain of influenza.

Tests have revealed that a second outbreak in Romania was also caused by the H5 type of virus, but scientists are waiting to confirm whether it is the same subtype responsible for the epidemic among poultry in Asia.

Government officials played down the increase in risks to British poultry farmers, saying that a contingency plan had been put in place to tackle an outbreak. Debby Reynolds, the chief veterinary officer at the Department for Environment, Food and Rural Affairs, said that a new risk assessment would be made once she had consulted experts on migrating birds, which are thought to have imported the H5N1 virus to Turkey. "It's the first time that this virus, which has been found in Asia, Russia, Mongolia and China, has been found so close to Europe," Dr Reynolds said.

"There is a risk to the UK, we've always said there was. We said the risk is low and we'll update that after we've taken full advice from the bird-migration people."

The Dutch government has ordered all poultry farmers to move their stock indoors to lessen the risk of infection by wild birds but Dr Reynolds said Britain would not follow its example. "Keepers should feed and water their birds indoors wherever possible. That does reduce the likelihood of infection," she said. "But housing birds would be a very serious step and it's not one to be taken lightly. "

The outbreak on a turkey farm in Balikesir, north-western Anatolia, was detected on 1 October and Turkish officials informed the European Union last Sunday. All of the farm's 1,800 turkeys, which were kept outside, were destroyed.

Scientists at the Government's Veterinary Laboratory Agency in Weybridge, Surrey, an EU reference laboratory for bird flu, confirmed yesterday that the outbreak was caused by the same H5N1 strain that had spread among poultry in Asia.

Dr Reynolds said the outbreak in Turkey did not affect the contingency plan already in place to eradicate the virus should it spread to British poultry. "We would immediately respond to stamp out the infection," she said. "We've got the measures set out in our contingency plan. Culling is one part of the story."

Professor Maria Zambon, head of the national influenza laboratory at the Health Protection Agency, said there was no need for the Government to change its existing policy. "The risks are unchanged by this particular event because the question of an avian virus becoming a human virus and capable of human-to-human transmission requires quite considerable genetic change."

There have been at least 117 cases of avian flu infecting people in the current outbreak in Asia; nearly all of the patients had direct physical contact with live birds. Scientists fear, however, that the longer this virus circulates among birds the greater the chance of it mutating into a form that is capable of transmitting more easily from person to person. "We don't understand exactly what could be required to make avian virus a fully human virus," Professor Zambon said.

But she dismissed suggestions that the outbreaks in Turkey and possibly Romania automatically increased the risk of a human pandemic.

"The fact that those birds are in Romania as opposed to south-east Asia doesn't change the threat to the human population," Professor Zambon said. "The risk of that virus becoming a human virus is the same whether it's in Romania or whether it's in south-east Asia."

Professor Zambon also dismissed the suggestion that the Government was being complacent. "It would be quite wrong to say there is no perception of risk and no planning for an eventual pandemic," she told journalists.

How great is the threat?

What is bird flu?

It is an infectious disease of birds caused by a similar group of viruses that cause influenza in humans. Wild birds can carry avian influenza and pass it on to domestic poultry including chickens, ducks and turkeys.

Is bird flu dangerous to humans?

Normally the viruses responsible for bird flu do not affect humans but occasionally they can infect people and cause quite serious illness. It is now known that the outbreak of "Spanish flu" in 1918 which killed an estimated 50 million people was caused by a strain of avian flu that infected humans. The current outbreak of bird flu in Asia is caused by a strain of virus called H5NI and when it manages to infect people it is highly lethal, killing up to half of those who develop symptoms.

What are the symptoms of bird flu?

In birds, the virus infects the intestines and is transmitted in faeces. Often the birds get sick and die. Sometimes they appear healthy enough to fly long distances. In humans, the symptoms range from typical flu-like symptoms such as fever, coughs, sore throats and muscle aches to eye infections, pneumonia and severe respiratory diseases and other life-threatening conditions.

How does bird flu spread?

Infected birds shed virus in saliva, nasal secretions and faeces. Some water fowl are thought to carry the virus with them when they migrate and they could transmit the infection to domestic poultry kept outdoors. Humans can pick up the virus when they handle live birds or when they come into contact with bird droppings. So far the virus has not developed the ability to transmit easily between one person and another, although some scientists believe this is probably only a question of time. If so, a deadly pandemic on a par with the 1918 outbreak is a serious possibility.

Is there any cure for bird flu in humans?

No vaccines are ready to protect people against infection, although some are being developed. Two commonly used antiviral drugs, amantadine and rimantadine, do not work against the H5N1 strain, but two other antivirals, oseltamavir (Tamiflu) and zanamavir are effective, although zanamavir (Relenza) is too complicated to administer.

Does the appearance of H5N1 in Turkey affect the risk of a human pandemic?

The World Health Organisation says that the more birds and people in the world that become infected with this strain of bird flu, the greater the chances of it mutating into a form that is more easily spread from person to person. Because people and birds live in close proximity in south-east Asia, the chances of an infectious form of H5N1 arising there is greater than in most other parts of the world. However, it does not bode well that the H5N1 virus is now on the doorstep of Europe, which has thousands of outdoor poultry farms.