A top bird flu expert on Tuesday predicted that the H5N1 virus will not reach the United States this year via migratory birds, but warned it will eventually arrive — possibly through infected birds smuggled into the country.

Robert G. Webster, a virologist at the St. Jude Children's Research Hospital in Memphis, Tenn., said it has been historically rare for bird influenza viruses to reach the Americas from Europe.

He said infected birds being smuggled into the U.S. pose a bigger threat right now than fears that migratory birds en route to America might mix with infected birds from Europe or Asia.

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"While wildlife people in the United States are watching for the appearance of this virus, I would suspect that it may not come this year," he told The Associated Press.

"If it doesn't come this year, don't relax, because it will eventually come," said Webster, who is in Singapore ahead of a two-day conference this week that is expected to draw many of the world's leading scientists on bird flu.

The H5N1 bird flu virus began ravaging Asian poultry stocks in late 2003 and has since killed at least 113 people worldwide. So far, most human cases have been linked to contact with infected birds.

Experts, however, fear the virus will mutate into a form that easily spreads from person to person, potentially sparking a global pandemic.

Webster said he's most concerned about the virus becoming established in the world's wild bird populations. He said most highly pathogenic avian viruses usually do not last long in nature. They typically start in wild birds, infect domestic birds and eventually die out.

"This one has broken the rules and gone back from the domestics into the wild birds. Is it going to be perpetuated there as a killer? That's the million dollar question," he said. "Will that virus go to the breeding grounds in Siberia and Africa and come back again? If it does, then the chances are eventually it will learn to go human to human."

Webster, who's been researching bird influenza for decades, said the spread of the virus to Africa is especially worrying because of the lack of infrastructure, political instability and a health system already overrun by diseases like HIV/AIDS.

With "all of those things going on in Africa, you could get human-to-human transmission started and not have the opportunity to do anything about it until it's out of hand," he said.

John Oxford, a professor of virology at Queen Mary's University of London, agreed that Africa is a major concern, but said attention should not be diverted from Asia.

He said countries should learn from recent catastrophes like the Indian Ocean tsunami and Hurricane Katrina in the U.S., that warning systems and preparedness plans must be implemented instead of just being discussed.

"They had been warned, but they didn't take any notice," he said of the natural disasters. "It's all very boring for these politicians to have all these scientists knocking at their doors saying, 'You'd better be careful. This is a threat.'"

He said the recent recreation of the 1918 Spanish flu, which killed up to 40 million people and sickened an estimated 20 percent to 40 percent of the world's population, has allowed scientists a rare chance to compare what happened back then to the situation today.

"Are we all running around the world telling people it's Armageddon and all that's happened is 100 people have died?" Oxford said. "I see this as like 1916. You have to learn from what happened. You cannot persuade yourself and other people that this is nothing."