If birds bring flu, what you should do

(Correction: Because of an editing error, a story on avian flu in yesterday's Health/Science section mischaracterized the bird flu's ability to spread among humans. So far, all the human cases have been among people who had intense, prolonged exposure to sick birds. No person is known to have been infected with avian flu by another person, and there is no evidence that the current genetic form of the virus can spread from person to person.)

The voice on the other end of the phone was calm -- but concerned.

''She had a question," recalled Tom Lyons, the Boston public health official who took the woman's call a few weeks ago. ''Could she feed the ducks at Jamaica Pond?"

It was a query for our times: With the specter of avian influenza just a continent away, the ordinary suddenly seems capable of igniting the calamitous. After all, news reports regularly chronicle the deaths of thousands of birds as the virus moves westward from Asia -- as well as of people who came into close contact with infected birds. Since 2003 the virus has sickened 192 people, killing 109.

What if the virus-laden birds land here?

Will it be safe for your children to play outdoor soccer? Should you abandon plans for a picnic on a lush meadow? And, before you clamber aboard the subway, would it be smart to don a mask?

''I can certainly understand why people worry, but the level of anxiety should be relatively low," said Dr. Paul Biddinger, a Harvard School of Public Health specialist in emergency preparedness. ''You're not going to get this from the sparrow on the corner or the duck on the pond. There's no way short of handling the diseased bird or putting your hand in bird excrement that you're going to come into contact with it."

The message, then: Don't panic.

But, at the same time, specialists warn: Don't ignore the possibility of some kind of global flu epidemic in humans.

Since an especially virulent strain of avian flu known as H5N1 emerged three years ago, disease trackers have watched it sweep across Southeast Asia and, in more-recent months, the Middle East and parts of Africa and Europe. Just last week, a swan killed by the disease was found in Scotland, the first time a wild bird carrying avian flu was found in the British Isles.

Is it definitely headed in our direction? And, if so, how soon?

''I don't know exactly when -- and there are various opinions about that -- but, personally, I think, yes, it will come here," said Stephen Morse, a virus specialist at Columbia University's Mailman School of Public Health. ''Given time, I would expect this will eventually become worldwide in birds. We have a similar example in West Nile virus. It had been spreading and spreading, and I think something similar is very likely with this."

But opinions clash on how, exactly, avian influenza will make its North American debut.

The most widely espoused theory involves birds making their annual treks northward, to summer in temperate zones. One popular spot is the Bering Strait, which separates far eastern Russia and far western Alaska.

There, waterfowl from Asia consort with waterfowl from North America in an annual mating ritual.

''During the summer months, they all sort of mingle in the northern part of the Northern Hemisphere," said Purdue University veterinarian Harm HogenEsch. ''It's very likely that there will be an exchange of virus, and when they migrate back in the fall, then it's likely that some of the migratory birds will carry the virus to North America."

And people like Rebecca Harris will be watching for them. She's coordinator of SEANET, a four-year-old consortium of government agencies, wildlife specialists, and volunteers that monitors bird deaths along the Northeastern US coastline.

That network, as well as scientists in Alaska, are searching for evidence of avian influenza.

''That's why the Alaska surveillance efforts have been the highest focus," said Harris, an avian ecologist at the Cummings School of Veterinary Medicine at Tufts University. ''But obviously, it's going to be important to have surveillance throughout the country, because it could get past you."

By rapidly recognizing flu in wild fowl, veterinarians hope to prevent infection of poultry flocks, which would force farmers to slaughter their remaining chickens and turkeys.

Robert Cook, chief veterinarian for the Wildlife Conservation Society, which runs the Bronx Zoo, said surveillance must also focus on illicit wildlife trafficking, which allows dealers to escape government tests of animals. Illegal trading has been blamed for earlier outbreaks of animal-borne disease in the United States.

''It's distressing that so much of our focus is turned northward, looking for migratory birds," Cook said. ''There's at least as much possibility that it could come in another way sooner, and let us not be caught unprepared or unaware."

Given the seeming inevitability of avian flu's arrival in the United States, authorities are already crafting their remain-calm-do-not-panic entreaties.

Those messages, though, are based on the expectation -- and hope -- that the H5N1 virus will not acquire the ability to infect people easily. So far, human cases have been reported only after victims had intense, prolonged exposure to sick birds. There has been no evidence that the virus in its current genetic form spreads person to person.

Even amid cramped conditions in Southeast Asia, the cradle of bird flu, the virus has affected relatively few people.

Further diminishing chances of human exposure in the United States: Here, chickens are generally sequestered in enclosed quarters, preventing exposure to infected bird droppings.

''It's not that I'm not concerned" about avian flu, ''that I'm saying, 'Oh, forget about it,' " said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. ''But just the very fact that a migratory bird might be seen in this country with avian flu does not cause me a great deal of concern."

Specialists said there's no reason to worry about eating chicken if bird flu is found here because cooking kills the virus. And there's no reason to restrict outdoor activities. HogenEsch, the Purdue veterinarian, says his daughter plays soccer outside, and he has no intention of telling her to leave the playing field upon the arrival of the avian virus. Even if a soccer player came into contact with tainted bird droppings, soap and water should wash away the threat.

The advice is different for felines: Vets in Asia and the Middle East have reported cases of outdoor cats contracting the illness after eating birds, so specialists recommend that cats remain indoors if avian flu arrives here.

Still -- and this, specialists acknowledge, is the big if -- recommendations would change profoundly if H5N1 gained the genetic machinery to trigger a long-feared worldwide outbreak of human illness known as a pandemic.

That's why they're recommending that families begin taking modest steps to prepare for a global epidemic: laying in a several weeks' supply of water, nonperishable food, and medication for chronic conditions such as heart disease and diabetes as well as over-the-counter pain and fever relievers. They recommend against buying scarce antiflu drugs such as Tamiflu.

But authorities concede that those preparations aren't practical for everyone: In some cases, people simply don't have the space in urban apartments. In others, there's barely enough money to buy that week's groceries, let alone reserves.

''My feeling about H5N1," Columbia's Morse said, ''is it's absolutely right to be watching this carefully."

Stephen Smith can be reached at stsmith@globe.com.