The federal government is boosting its effort to look for bird flu in migratory birds, planning to test five to six times as many birds this year alone as it has screened since 1998.

Much of the effort will focus on Alaska, where scientists worry that birds arriving from Asia — beginning next month — will bring in the H5N1 virus and pass it along to other birds, which will fly south this fall.

Scientists had already been watching for the deadly flu strain in wild birds in Alaska and North American migratory flyways. But the effort is being dramatically stepped up this year, said John Clifford, chief veterinarian for the U.S. Department of Agriculture, which is working with other agencies on the program.

Scientists will study live birds, others that are found dead or killed by hunters, and environmental samples that might carry the worrisome form of bird flu. While most concern about birds flying south through the United States focuses on their Pacific route in the western states, 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 USDA. 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: importing and smuggling of birds.

The chief concern about the H5N1 flu in wild birds is that the virus might make its way to some of the 10 billion or so chickens produced every year in the United States. That could damage the poultry industry and pose a hazard for people who work with chickens. Virtually all bird flu cases in people reported so far are blamed on close contact with infected poultry.

Human cases are uncommon, but scientists worry that the virus may mutate into a form that can pass easily between people. 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 there's no guarantee that Alaska is where the virus will first arrive in North America, or that it will follow recognized flyways from there, says Ken Rosenberg, director of conservation science at the Cornell Lab of Ornithology in Ithaca, N.Y.

Migrating birds can show up "virtually anywhere and come from virtually anywhere. That's just the nature of birds and bird migration," he said.

Rosenberg said he expects the deadly flu now wreaking havoc in Asia and parts of Europe and Africa will show up in wild birds in the United States, and "I wouldn't be surprised if it will be within the next year." It might not appear in an outbreak that kills many birds, but rather in isolated cases, he said.

Rosenberg also said he's heard reports of people wanting to slaughter wild birds to protect against bird flu. "From a conservation perspective that would be a horrible thing to do, and it would be totally unwarranted given the situation we have today," he said.

Peter Marra of the Smithsonian Migratory Bird Center at the National Zoo in Washington said it's clear migratory birds have played a role in the spread of bird flu elsewhere, and that Alaska is an important place to look for it. But that's not the only way the virus could reach the United States.

"I would say movement of birds through the illegal pet trade is probably the most likely way it's going to get here," Marra said.

That's just a guess, he quickly added, but there is precedent. Taiwan, where bird smuggling is common, confirmed last October that its first case of H5N1 bird flu appeared in birds smuggled from China. A Nigerian official has also blamed illegal poultry imports for delivering the virus to that country.

Clifford agreed that smuggling birds or bird products is a possible route into the country, and said the government will boost its anti-smuggling efforts as well. Those efforts include not only inspections at the border, but also teams within the United States that survey exotic food markets, live bird markets and restaurants for signs of illegal animals.

As for legal imports, virtually all live birds that enter the United States have to go through a 30-day quarantine and be tested for bird flu and other viruses, Clifford noted. The government doesn't allow imports of birds from countries that have H5N1 in poultry flocks.