Flu pandemic? Maybe not

History is supposed to teach lessons. But past flu pandemics, it turns out, don't teach much about whether today's bird flu will become a human mega-killer or just make some scientists and officials look like Chicken Little.

In a viral sense, the sky has fallen three times in the last century — 1918, 1957 and 1968 — when "super-flu" strains killed millions more people than annual flu epidemics routinely do.

Back then, there weren't surveillance systems or modern genetic tools to detect and document viruses as they evolved into killer strains. Because scientists don't know how that evolution happened or how long it took, they can't tell us whether what we're seeing with bird flu now is the run-up to a pandemic or a near miss.

"My crystal ball doesn't allow me to answer that," said Dr. Frederick Hayden, a University of Virginia flu expert.

Leading scientists now discount the notion that flu pandemics happen in regular intervals and that the world is overdue for a new one.

They don't even agree on how bad it is that bird flu has spread to more types of birds. Instead of an appetite for people, the germ is showing a growing fondness for birds, some say.

They do agree on the need to make vaccine, stockpile drugs and be prepared.

"We have to run scared" and be glad if precautions prove unneeded, said Dr. Edwin Kilbourne, a longtime microbiologist and flu virus expert at Cornell University who is now an emeritus professor at New York Medical College.

Nobody can say when the next pandemic will emerge — just ask Kilbourne. When "swine flu" appeared in 1976, following global flu epidemics in 1957 and 1968, he championed the idea that pandemics appear every 10 years or so. But swine flu didn't become a pandemic, and neither has anything else in the three decades since then. Clearly, Kilbourne says now, the notion of regularly timed pandemics is wrong.

The first documented cases of bird flu in people occurred in 1997 in Hong Kong, where six people died and the entire poultry population of about 1.5 million birds was slaughtered in three days to control the outbreak. The current flu virus strain, classified as H5N1 like the Hong Kong germ, appeared in people in 2003. More than 60 people in Asia have died, and more than 150 million chickens and ducks have died from the germ or been slaughtered.