Vietnam on Thursday confirmed the sixth human death from bird flu (search) in three weeks and neighboring Thailand recorded its first case among poultry this year as health experts expressed concern about a possible repeat of last year's devastating outbreak.

About 330,000 birds have died or been slaughtered because of the virus in Vietnam this year, and the World Health Organization is worried infection could spread rapidly with the start of the Feb. 9 Lunar New Year (search) holiday. Chicken is the centerpiece of Vietnamese meals during the festivities known as Tet (search).

"Since Tet is a time when people are traveling and more poultry is going to the market ... there is, of course, a high risk of the spread of the virus and infection," said Hans Troedsson, WHO's representative in Vietnam.

Troedsson said there is an urgent need for more research to better understand some of the mysteries surrounding the disease, including the ways in which it is transmitted and why it tends to often affect younger people, especially children.

WHO and other health experts fear that avian influenza could evolve into the next global pandemic if the virus mutates and human-to-human transmission occurs. There is, however, no evidence of that yet.

Last year the outbreak appeared in 10 Asian countries, killing or forcing the slaughter of more than 100 million birds and jumping from poultry to people in Vietnam and Thailand, where 26 and 12 people died respectively since last year.

An 18-year-old woman became the sixth victim in Vietnam this year after eating an infected chicken, officials said Thursday. No one else in her family, including her sister who slaughtered the bird, showed any sign of the disease.

The government in Hanoi has placed the country on alert and urged greater caution, but the domestic sale and transport of poultry has not been banned in Vietnam as it was last year during the Tet holiday.

"I eat it and I will continue to eat it during Tet," said Nguyen Van Phuong as he left Hanoi's largest poultry market carrying two live ducks. "I'm worried about my life, but I'm reassured all the poultry here is healthy."

Thailand on Thursday reported its first confirmed case of bird flu in poultry in two months. Tests performed following the death of a chicken on Jan. 12 showed that some of the 20 birds slaughtered as a precaution carried the deadly H5N1 strain of bird flu.

Members of the family in eastern Thailand that raised the poultry were also tested for the virus, but the results were negative.

Vietnam has banned the import of poultry from neighboring countries and 200,000 pamphlets have been distributed in Ho Chi Minh City advising people to avoid eating birds and from coming into contact with them.

The WHO also has cautioned against transporting poultry from places affected by bird flu to areas devastated by last month's tsunami. The agency stressed that infected poultry must be "kept out of the food chain, including emergency food relief activities."