An 18-year-old man passed away at a hospital in Ho Chi Minh City, becoming the ninth person to die from bird flu in Vietnam, a medical official said.
The man from the Koho ethnic minority group in the Central Highlands province of Lam Dong died in the early hours of Monday morning, Tran Tinh Hien, deputy director of the city's Tropical Disease Hospital, said.
"He was admitted to our hospital on Thursday and on Saturday he tested positive for H5N1," he said. "According to our information he had direct contact with chickens in his village in the Di Linh district."
The victim is the 11th person confirmed to have contracted the H5N1 strain of avian influenza in Vietnam, nine of whom have died.
A four-year-old boy has made a full recovery, while an eight-year-old girl is in a stable condition at the Tropical Disease Hospital, Hien said. Dozens more remain hospitalised as suspected cases.
Human-to-human transmission possible
The World Health Organization said it could not confirm the latest death.
The World Health Organisation (WHO) said human-to-human transmission of bird flu was a "possible explanation" for two deaths in Vietnam, in what could be a first in Asia's latest bird flu crisis.
The WHO has already warned that avian flu's highly pathogenic H5N1 strain could combine with a human influenza virus to create a lethal new virus that could kill millions of people across the globe through human-to-human transmission.
Bird flu has been recorded in 10 Asian nations since December and was blamed for 10 deaths last month, eight in Vietnam and two in Thailand.
The WHO said two Vietnamese sisters who fell ill on January 10 and died on January 23 in a Hanoi hospital could have contracted the lethal H5N1 strain of avian influenza from their dead brother.
"The investigation has not been able to conclusively identify the source of infection for the two sisters," the UN health agency said in a statement.
"However, WHO considers that limited human-to-human transmission, from the brother to his sisters, is one possible explanation."
The sisters, aged 23 and 30, are part of a cluster of four cases of respiratory illness in the northern province of Thai Binh. The cluster included the two sisters, their brother and his wife.
The brother died shortly before his sisters were admitted to hospital and no samples were available from him for H5N1 testing. His wife was admitted on January 13 at the same time as the two sisters, but has recovered.
In an apparent bid to play down concerns about humans passing the disease on to each other, the WHO cautioned that there was "no evidence of efficient human-to-human transmission of H5N1 occurring in Vietnam or elsewhere".
In China, where the new suspected outbreaks bring to 14 the number of suspected or confirmed outbreaks of bird flu, authorities worked feverishly to contain the disease as the WHO warned further cases could emerge in the days ahead.
Officials ordered the killing of chickens, closed down poultry markets and stepped up surveillance, as the WHO urged speedy measures to curb the virus which is now either confirmed or suspected in at least seven regions of the vast country, including as far away as Xinjiang in the far northwest.
"It's entirely conceivable that there could be more cases among poultry populations," Roy Wadia, a Beijing-based WHO spokesman, said hours before the latest outbreaks were announced.
"It seems to be spreading very fast. Time is of the essence, and you have to keep up with the outbreak," he said.
Since the killer H5N1 strain emerged in South Korea late last year, Asian nations have quickly fallen prey to the disease which is believed to be spread by wild migrating birds.
More than 33 million chickens, ducks and other poultry have been culled across the region to curb the virus which has killed eight people in Vietnam and two in Thailand and been detected in birds in eight other countries.
Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand and Vietnam have all reported outbreaks of H5N1 among poultry, while China's Taiwan Province and Pakistan have reported weaker strains.
In Thailand, where 18.4 million birds have been slaughtered, embattled Prime Minister Thaksin Shinawatra called for calm Sunday and insisted the outbreak was controllable.
"We can control it, no problem. Don't panic," Thaksin said.
The epidemic has spread to nearly half of Thailand's 76 provinces including the teeming capital Bangkok, and 14 suspected bird flu cases including seven deaths are listed.
The premier, whose credibility has suffered amid accusations that his administration covered up the outbreak, appealed for public calm by stressing that no human-to-human transmission of avian flu had been recorded in the kingdom.