The bird flu virus that has killed 36 people in Vietnam may not be contained until 2007 because the way it is spreading still baffles experts, officials said Monday.

The government aimed to contain the H5N1 virus by next year or 2007 and eliminate it by 2010, Deputy Agriculture Minister Bui Ba Bong told a conference reviewing the fight against bird flu in Vietnam, the country hit hardest by the epidemic.

Other senior officials said current knowledge about the virus, which has been at its worst during the cool season between December and March in each of the last two years, meant the fight would be a tough one.

“This is a new, extremely dangerous disease which contemporary knowledge in our country and internationally has not been able to explain properly,” Deputy Prime Minister Nguyen Tan Dung said.

He told health, agriculture officials and foreign experts it was still not known for sure how the virus was transmitted from waterfowl, which can carry it without getting sick, to poultry and then to people.

“There are cases where a healthy person carries the virus without showing clinical symptoms, which has made the risk of spreading the virus in the community greater,” Deputy Health Minister Tran Chi Liem said.

What Vietnam knows for sure is that H5N1 has killed 36 of the 71 people known to have contracted the virus since it swept across much of Asia in late 2003.

What the World Health Organization fears is that the virus will mutate into a form that can pass easily between people and millions will die in a global pandemic.

FEAR

“If the virus changes, it will be the biggest global health crisis,” said Hans Troedsson, the WHO representative in Vietnam, predicting “50 to 100 million deaths in the worst situation.”

“We are facing a serious situation not only in Vietnam, but in the region of avian influenza,” he said. “There is an extremely short window to contain the virus if the virus changes.”

If the virus mutated, the first 20 people with it could infect 800 others in 10 days and a pandemic would have to be stifled within that brief period, he said.

“SARS will be nothing compared to the avian influenza pandemic. Let’s work together,” said WHO’s Troedsson, referring to the Severe Acute Respiratory Syndrome outbreaks in 2003 that killed nearly 800 people worldwide, five of them in Vietnam.

Bird flu has killed 51 people in Asia - 36 Vietnamese, including 15 since December, 12 Thais and three Cambodians - since arriving in Asia in late 2003, brought probably by migrating wild fowl.

A ban on hatching and raising waterfowl until June 30 would be extended until the end of the year, Bong said.

Given the bird flu is likely to recur between December and March, Southeast Asia’s cool season, the ban should be extended to February 2006 at least, a senior provincial official said.

“The extended ban will be supported by farmers, and we will enforce the rule anyway,” said Nguyen Duy Long, head of the animal health department of Long An province in the Mekong Delta, where the virus erupted again in December.

The one-day conference in Hanoi was expected to decide if all waterfowl carrying the H5 component of the bird flu virus in the Mekong Delta would be slaughtered.

But the government left it open to scientists to decide if all ducks carrying H5 viruses should be killed, an Agriculture Ministry spokeswoman told Reuters.