Vietnam has asked the United Nations for help in battling the avian flu that has killed more than a dozen people in a month. That help may force the country to modernize its poultry trade.

The squawks of a chicken having its throat cut in an open-air market are a familiar sound for most people in Vietnam - especially now, in the week leading up to the Tet Lunar New Year. Boiled chicken is a traditional Tet meal, and discriminating customers insist their chickens be killed in front of them to ensure freshness.

But as Vietnam prepares to greet the Year of the Rooster next week, there are growing fears that it may also be the year of the bird flu. The H5N1 flu virus that killed 20 in Vietnam last year has returned, killing 13 people in the past month and spreading to more than half the country's provinces.

Wednesday, Vietnam formally asked the United Nations for help in controlling the virus.

The United Nations welcomed the request, as did the country's embattled poultry industry that has lost millions of dollars to the avian flu.

At a Hanoi market, 48-year-old Le Van Van says his sales are down more than 75 percent and he is glad the government is admitting it needs help.

The poultry salesman says he thinks the government has not done enough to fight the virus, and surveillance on chicken transport has not been strict enough.

Bringing bird flu under control may force changes in the way chickens are raised and slaughtered in Vietnam. Ho Chi Minh City, in the south, has already banned live chickens in markets, and it is likely that U.N. experts may recommend the same for the rest of the country.

Thus far, most of the people who have contracted avian flu in Asia caught it from sick poultry. But health experts warn that the virus could change to spread among humans, and that might lead to a global pandemic that could kill millions.

Hans Wagner, an animal health officer with the U.N. Food and Agriculture Organization, says the only way to stop the virus is to eliminate it at the source - in chicken and duck flocks.

"The more human cases you get, the more the risk also that a mutation may occur and a human-to-human transmission may occur," Mr. Wagner says. "So the important thing is to address the problem in the poultry domain. That is where we have the major work to do."

Modernizing Vietnam's poultry industry could take years, but health experts say painful changes will have to be made.

The H5N1 virus has killed more than 40 people in Southeast Asia since it re-appeared in Asia in late 2003. The virus originally appeared in 1997 in Hong Kong, killing several people before the government slaughtered all the city's poultry, halting its spread for several years.