NEW YORK -- The US government is boosting its effort to look for avian flu in migratory birds, and is planning to test five to six times as many birds this year as it has screened since 1998.
Much of the effort will focus on Alaska, where scientists have voiced fear that birds arriving from Asia -- beginning next month -- will bring in the H5N1 virus and pass it to other birds, which will fly south this fall.
Bird flu, which is spreading across Asia, Europe, the Middle East, and Africa, is expected to jump across the Atlantic Ocean to the Americas within a year, a senior UN official said yesterday.
''It is certainly within the next six to 12 months. And who knows . . . it could be earlier," said Dr. David Nabarro, coordinator of the UN drive to contain the pandemic in birds, and to prepare for its possible jump to humans.
He predicted that the spread across the Atlantic Ocean would take place in two stages, carried in the next few months by wild birds flying from West Africa to the Arctic region, and would be brought southward to North and South America six months later.
Scientists have been watching for the flu strain in wild birds in Alaska and North American migratory flyways. But the effort is being stepped up this year, said John Clifford, chief veterinarian for the US Department of Agriculture, which is working with other agencies on the program.
Scientists will study live birds, those that are found dead, or those that are killed by hunters.
The scientists will also check environmental samples that might carry the bird flu. While most concern about birds flying south through the United States focuses on their Pacific route, other migratory paths will be included, Clifford said.
The goal is to test 75,000 to 100,000 live or dead birds this year, said Angela Harless of the Department of Agriculture. The testing, which will also include some Pacific Ocean islands, will focus on waterfowl and shorebirds.
At the same time, Clifford said, officials will continue to monitor other activities that may introduce the virus to the United States: the importing and smuggling of birds.
The chief concern about the H5N1 flu in wild birds is that it might spread to some of the roughly 10 billion chickens hatched every year in the nation.
Scientists have voiced concern that the virus may mutate into a form that can pass easily among humans. That could lead to a worldwide flu epidemic.
It makes sense to focus the wild bird monitoring on Alaska, but migratory routes are so complex that there is no guarantee that Alaska is where the virus will first arrive in North America, or that it will follow flyways from there, said Ken Rosenberg, director of conservation science at the Cornell Lab of Ornithology in Ithaca, N.Y.