The avian influenza virus that has devastated poultry stocks across Asia and killed 61 people could mutate into a form that is highly contagious among humans.

Dr. Lee Jong-wook said the World Health Organization hopes to initially acquire 1 million doses of the anti-viral Tamiflu, which is the only drug known to be effective against avian influenza in humans.

He said talks are under way with other countries and Swiss drug manufacturer Hoffmann-La Roche Inc. to allow the medicine to be distributed to poor countries for free or at highly discounted rates.

Currently WHO has only enough Tamiflu to treat about 125,000 people, he said.

Virus Doesn't Carry a Passport

"Clearly for us and for others this is very important -- to deal with the problem at the source," he told reporters in Bangkok where he was attending a global conference on health promotion. "WHO has a very limited stock. We want to increase the stockpile and we would like to deploy this to countries in this region."

Lee also warned that it makes no sense for wealthy countries to horde large volumes of either the drug Tamiflu or an experimental vaccine that has recently shown promise in humans.

He said the best way to control the virus if it begins spreading among humans is to hit it hard at the source, with wealthier countries sharing their drugs.

The United States already has enough Tamiflu to treat 2.3 million people and is working to acquire more, while Britain, France, Finland, Norway and New Zealand are placing orders that would cover between 20 percent and 40 percent of their populations.

"It doesn't really make sense (to say) 'This is mine. We will wait until the problem hits us and use this,'" Lee said. "On a map, we deal with boundaries, but the virus doesn't carry a passport or visa."

Old-Fashioned Surveillance

Bird flu has devastated poultry stocks across Asia and killed 61 people in the region since late 2003, with the latest death reported Tuesday in Vietnam. Most cases have been traced back to contact with poultry, but Lee said WHO is concerned the virus could mutate into a form that is highly contagious among people.

Researchers have recently published models outlining plans that could help control the spread of disease if the virus starts spreading from person to person. They recommend implementing quick quarantines, travel restrictions and distributing large quantities of drugs for people living near the outbreak.

Lee said the models, drugs and vaccines are all tools that can be used to prepare for a pandemic, but none of it may prove effective in reality if the virus alters severely. He stressed the importance of old-fashioned surveillance, both in detecting cases and in monitoring changes in the genetic makeup of the virus.

Two of the last three global pandemics originated in Asia. The Asian flu of 1957-58, first identified in China, and the Hong Kong flu of 1968-69 each killed more than 1 million people. Neither compared to the Spanish flu of 1918-19, which killed up to 40 million people and sickened an estimated 20 percent to 40 percent of the world's population.