The discovery of swine flu in birds in Chile raises concerns about the spread of the virus, the UN warns.

Last week the H1N1 virus was found in turkeys on farms in Chile. The UN now says poultry farms elsewhere in the world could also become infected.

Scientists are worried that the virus could theoretically mix with more dangerous strains. It has previously spread from humans to pigs.

However, swine flu remains no more severe than seasonal flu.

Safe to eat

Chilean authorities first reported the incident last week. Two poultry farms are affected near the seaport of Valparaiso.

Juan Lubroth, interim chief veterinary officer of the UN Food and Agriculture Organization (FAO), said: "Once the sick birds have recovered, safe production and processing can continue. They do not pose a threat to the food chain."

Chilean authorities have established a temporary quarantine and have decided to allow the infected birds to recover rather than culling them.

It is thought the incident represents a "spill-over" from infected farm workers to turkeys.

Canada, Argentina and Australia have previously reported spread of the H1N1 swine flu virus from farm workers to pigs.

Dangerous strains

The emergence of a more dangerous strain of flu remains a theoretical risk. Different strains of virus can mix together in a process called genetic reassortment or recombination.

So far there have been no cases of H5N1 bird flu in flocks in Chile.

However, Dr Lubroth said: "In Southeast Asia there is a lot of the (H5N1) virus circulating in poultry.

"The introduction of H1N1 in these populations would be of greater concern."

Colin Butter from the UK's Institute of Animal Health agrees.

"We hope it is a rare event and we must monitor closely what happens next," he told BBC News.

"However, it is not just about the H5N1 strain. Any further spread of the H1N1 virus between birds, or from birds to humans would not be good.

"It might make the virus harder to control, because it would be more likely to change."

William Karesh, vice president of the Wildlife Conservation Society, who studies the spread of animal diseases, says he is not surprised by what has happened.

"The location is surprising, but it could be that Chile has a better surveillance system.

"However, the only constant is that the situation keeps changing."

http://news.bbc.co.uk/2/hi/science/nature/8224923.stm