The World Health Organization is concerned about the reported death of at least one person in Vietnam from a particularly deadly strain of the bird flu virus. The United Nations agency has asked Vietnam for samples of the virus, to confirm that it is the same strain that killed chickens and humans in the region earlier this year.

According to the World Health Organization, the Vietnamese government says it found the deadly H5N1 strain of the bird flu virus in one of three people who died recently of bird flu. The U.N. organization says it has asked the Vietnamese health ministry for samples to send to an outside laboratory for independent confirmation.

The Vietnamese say they are investigating three separate suspected bird flu deaths in the southern province of Hau Giang, and they say eight more people suspected of being infected with the virus are in the hospital.

The H5N1 virus swept across Asia last January, killing 16 people in Vietnam and eight in Thailand. Most of the victims had handled infected chickens. H5N1 also killed millions of chickens and ducks, and prompted governments across the region to order the culling of millions more in order to stop the virus's spread.

Peter Cordingley, spokesman for the Western Pacific office of the World Health Organization, says WHO is asking Vietnamese officials for permission to bring a team of epidemiologists into the country to study the latest cases.

Mr. Cordingley says WHO is worried that the virus could change into a form that can be transmitted between humans, which could lead to a global pandemic. "Each time this virus does cross, [there is a chance] of it mixing with the human flu virus in somebody who contracts the avian flu virus and then [producing] a completely new virus against which there is no immunity," he said. "This is a public health element that concerns WHO."

Mr. Cordingley says governments in the region are taking the threat of bird flu seriously. But he says the disease mainly strikes chicken flocks in the countryside, where there are not enough people to keep watch. He says it is still too early to tell how serious the latest situation is.

"We're watching it very carefully. We don't know yet just how serious this situation is, information is sketchy," said Mr. Cordingley. "I mean this could blow through as isolated cases or it could be the beginning of something more serious."

The Thai government says a countrywide surveillance network has been established to report any possible bird flu infections in humans. Since the disease re-emerged in Thailand last month, the virus has been detected in fowl in 24 of Thailand's 76 provinces.

In recent months the virus has also resurfaced among birds in China and Indonesia.