Even if bird flu does arrive on U.S. shores on the wings of a migratory bird, the virus is unlikely to make the inroads in poultry — or in people — that it has in less developed countries, the nation's top avian influenza expert says.

"The surveillance is going to be so intense that it is very unlikely that there is going to be the type of situation we see everywhere from Nigeria to Indonesia," Dr. Anthony Fauci, the National Institutes of Health's infectious disease chief, said in an interview with The Associated Press.

Bird flu has killed 109 people in nine countries, mostly in Asia, according to the World Health Organization. It's also killed or forced the slaughter of more than 200 million chickens, ducks, turkeys and other domestic fowl in Asia, Europe and Africa. Though experts believe migrating birds could spread the virus to the United States this year, Fauci has his doubts.

"One migratory bird does not a pandemic make," Fauci said, adding that U.S. poultry farmers — like their colleagues in Europe — keep their birds isolated from contact with wild birds. Most people in the United States, in turn, have limited contact with poultry or their droppings that, if the fowl were infected, would contain high levels of virus.

In Europe, despite an initial "spike of anxiety," farmers know now bird flu is something to keep an eye on, he said. The same should be the case here.

"It won't be what you see in countries in which there is no regulation, in which there is no incentive to compensate farmers, in which the people, who are so poor, when they see their chickens are getting infected they immediately sell them or they don't tell anybody because they don't want them culled," Fauci said in Tuesday's interview. "That is a critical issue that is fundamentally different than what we see in Western Europe and that we will see in the United States."

Nor is the bird flu virus likely to change overnight so that it spreads from person to person, Fauci said.

To do that, the virus first must undergo a series of genetic changes — changes that ultimately could make bird flu even less virulent. Generally, the more easily a virus can be spread, the less virulent it is, he said.

Scientists might see the signs of change while studying the virus itself, but an early warning would be if doctors or nurses caring for someone who caught the H5N1 strain from a bird in turn got sick, something that hasn't happened anywhere yet, Fauci said.

"It is entirely conceivable that this virus is inherently programmed that it will never be able to go efficiently from human to human," Fauci said. "Hopefully the epidemic (in birds) will burn itself out, which epidemics do, before the virus evolves the capability of being more efficient in going from human to human."

The government still must prepare for the worst — "it would be unconscionable not to" — as officials gear up should bird flu spark a human pandemic, he added.

To prepare, Fauci recommended families stock up on supplies, including canned food and water, as they would anyway for a hurricane or winter storm. People who require regular medication for diabetes or other chronic illnesses should have an extra week or two supply, like they would for a vacation.

The public, however, should worry only if bird flu begins showing signs of evolving into more of a human threat. In that case, airline passengers arriving from an afflicted area would pose a greater threat than any chicken, Fauci said.

Were a full-blown pandemic to emerge, scientists are debating whether to vaccinate first those most likely to spread the virus, rather than those traditionally first in line for winter flu shots, including the very old, very young and chronically ill.

"At the end of the day, you have a broader, more favorable, beneficial effect on society by preventing the spread by vaccinating the spreaders — not the grandpa who sits at home watching TV and doesn't go out and spread it to anybody but is concerned about it coming into the house," Fauci said. "There has not been a policy change in that, but it is under very active discussion."