United Nations health officials say the bird flu that has led to the killing of tens of millions of chickens in Asia is not being transmitted from person to person, and they have played down reports that the virus has infected pigs in Vietnam. Either development could have been the forerunner to a human influenza epidemic.
The World Health Organization said Saturday that two sisters who died from the H5N1 strain of the avian virus earlier this month in Vietnam did not catch the virus from their brother, who also died from bird flu. The WHO said genetic tests showed that the virus from both sisters is of avian origin and contained no human influenza genes.
So far, at least 18 people have died from the virus in Vietnam and Thailand, and health officials have said all those who died caught the virus from close contact with infected chickens.
John Rainford, the WHO spokesman in Thailand, says the Vietnamese sisters died in the same way as the others, and not because they were infected with a mutated, or "recomposition," virus. "We knew that, what they had died of wasn't any kind of recomposition virus," he said.
Bird flu has devastated poultry industries across Asia, with 10 countries reporting confirmed outbreaks of avian flu. At least 50 million chickens in the region have been culled in efforts to stem the spread of the disease.
Health experts say their worry is that the avian virus could combine with the human influenza virus, and create a new strain of bird flu that could be passed from human to human. That could result in the type of pandemic that killed millions around the world in the last century.
On Friday, the U.N. Food and Agriculture director in Hanoi caused alarm when he said the H5N1 virus had been found in the nostrils of pigs in the Vietnamese capital. The report was worrying because health officials say pigs are a perfect vessel for the avian and human forms of the virus to mix and swap genes.
The FAO's headquarters in Rome quickly downplayed that report, saying the pigs lived on farms with infected chickens and could easily have inhaled infected chicken feces. The WHO's Mr. Rainford says the finding of the virus in the pigs' noses is preliminary, and even if that turns out to be the case, there is no evidence that the pigs have actually been infected with the disease. "It was very preliminary," he said. "You had a couple of nasal swabs, as I understand it, which would not comprise any kind of rigorous scientific study. It would be expected that there would be some measure of transmission [from chickens to animals] somewhere down the road, but they don't have any evidence that that's the case right now." A Vietnamese official said flatly Saturday that no pigs in the country had been infected.