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

联合国警告道，智利发生家禽类感染猪流感事件激起人们对病毒传播的顾虑。

Turkeys have caught swine flu in Chile

Last week the H1N1 virus was found in turkeys on farms in Chile. The UN now says poultry¹ farms（养鸡场，家禽场） elsewhere in the world could also become infected.

Scientists are worried that the virus could theoretically mix with more dangerous strains. It has previously² spread from humans to pigs.

However, swine flu remains³ no more severe than seasonal⁴ flu.

Safe to eat

Chilean authorities first reported the incident last week. Two poultry farms are affected⁵ near the seaport⁶ of Valparaiso.

Juan Lubroth, interim⁷ 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（隔离，封锁） and have decided⁸ to allow the infected birds to recover rather than culling⁹（挑选） 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 emergence¹⁰ of a more dangerous strain of flu remains a theoretical risk. Different strains of virus can mix together in a process called genetic¹¹ 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, vice¹² 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（观测系统）.

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