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Flu Fears

Bird flu has spread rapidly in the last few months, but how serious is the threat to humans?

By Denise Grady, Gina Kolata, Donald G. McNeil Jr., and Elisabeth Rosenthal

Over the last year, it has been impossible to watch TV or read a newspaper without encountering dire reports about bird flu and the possibility of a worldwide epidemic, or pandemic. First Asia, then Europe, now Africa: Like enemy troops moving into place for an attack, the bird flu virus, known technically as A(H5N1), has been steadily advancing. The latest country to report human cases is the former Soviet republic of Azerbaijan, where five of seven infected people have died. The virus has not reached the Americas, but it seems only a matter of time before it turns up in birds here.

Bird flu is what its name implies, an avian disease that has infected millions of birds but fewer than 200 people. Nearly all of them have caught it from close contact with birds.

But when people do contract it, it can be deadly. Bird flu has killed more than half of its known human victims—an extraordinarily high rate. Equally alarming is that many of those who died were healthy, not the frail type of patients usually thought to be at risk of death from influenza.

Even so, a human pandemic caused by bird flu is by no means inevitable. Many scientists doubt it will ever happen. The virus does not infect people easily, and those who do contract it almost never spread it to other humans.

Inevitable, or not?

Having observed bird flu for many years in Asia, Dr. Jeremy Farrar of the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam, thinks it is unlikely that the virus is poised to jump species, becoming readily transmissible to humans or among them. Nor does he believe that a horrific influenza pandemic is inevitable or long overdue.

"For years, they have been telling us it's going to happen—and it hasn't," says Farrar, who notes that people live in close contact with poultry in Asia. "Billions of chickens in Asia have been infected and millions of people lived with them ... and less than 200 people have gotten infected. That tells you that the constraints on the virus are considerable. It must be hard for this virus to jump."

But other experts disagree. Dr. David Nabarro, chief avian flu coordinator for the United Nations, describes himself as "quite scared," especially since the disease has broken out of East Asia and reached Europe and India much faster than he expected.

"That rampant, explosive spread, and the dramatic way it's killing poultry suggests that we've got a very beastly virus in our midst," Nabarro says.

Researchers have been looking to the 1918 influenza epidemic for lessons on how to handle today's bird flu. That epidemic killed 675,000 Americans in just a few months—more than World War I, World War II, the Korean War, and the Vietnam War combined. Worldwide, more than 21 million people died. Unlike most flu strains, which kill predominantly the very old and the very young, that one primarily struck young adults in their 20s, 30s, and 40s.

So what, if anything, does the 1918 case tell us about what is happening today? The answer is: a lot and not enough. There are many mysteries remaining. But the 1918 pandemic showed how quickly an influenza virus could devastate American towns and cities and how easily it could spread across the globe, even in an era before air travel. And it showed that a bird virus, which the 1918 flu began as, could turn into something that spreads among people.

Questions, and some answers

There are many things about bird flu that scientists do know. Here are answers to some frequently asked questions about bird flu:

· How will we know if the virus starts spreading from person to person?
If there is a pandemic, it would be everywhere, not just in one city or one country. One hallmark of a flu pandemic would be an unusual pattern of illnesses—lots of cases, possibly some that are more severe than normal, and maybe flu infections outside flu season.

· If bird flu reaches the U.S., where will it show up?
That depends upon what route it takes. If it's carried by migrating birds, it would likely appear first in Alaska or along the West Coast. But if the virus lurks in a bird being smuggled into the U.S., it could land in any international airport. Or an infected human could carry the virus into the country via any airport or across any border.

· When people die from bird flu, what kills them?
Most patients die because their lungs give out. The disease usually starts with a fever, fatigue, headache, and aches like a regular flu. Within days, it can turn into pneumonia, and the patient's lungs are damaged and fill with fluid.

· If bird flu reaches the U.S., will it be safe to eat poultry?
Cooking kills viruses, so as long as the meat is cooked thoroughly, there is virtually no risk of becoming infected.