Flue fears: bird flu has spread rapidly in the last few months, but how serious is the threat to humans?

• Author: Grady, Denise
• Position: INTERNATIONAL

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...