If the H5N1 avian flu begins to easily infect humans, it will move too quickly for drugs and vaccines to be of much use, Osterholm said.

"It doesn't matter if we have a vaccine now or not. We can't make it," Osterholm said in a telephone interview.

The H5N1 bird flu virus has killed at least 65 people in four Asian nations since late 2003, and has killed or forced the destruction of tens of millions of poultry.

Experts say it is mutating steadily and fear it will eventually acquire the changes it needs to spread easily from person to person.

If it does, it will sweep around the world in months or even weeks and could kill millions of people -- as many as 150 million, according to the most dire forecast by the World Health Organization.

When avian flu infects people it looks like any other flu with respiratory symptoms, fever and other common effects but it will kill many more than the 500,000 people who die of ordinary flu each year around the world.

People have known about the risk of an influenza pandemic for a very long time, said Osterholm, an infectious disease specialist at the University of Minnesota who advises the federal government on such issues.

"We have had a pandemic flu plan as a planning process since 1976," said Osterholm. "Nobody has completed it. It been one of the most long-standing incompleted processes in Washington. Nobody wants to believe that modern medical science can't handle something."

But it cannot, said Osterholm, who has seen the current US flu plan. The plan has not been published yet but leaked versions suggest the country has done little to prepare for an H5N1 pandemic.

Osterholm and other experts have long been complaining that there are not sufficient hospital beds, equipment or trained workers to cope with a major epidemic.

"The one thing I worry desperately about it is the impact of overreliance on neuraminidase inhibitors," he said.

There are two drugs in the class -- Roche and Gilead's Tamiflu, known generically as oseltamivir, and GlaxoSmithKline's Relenza.

They work to reduce the severity of annual influenza and may prevent infection if used at the right time. Tests suggest they also work against H5N1, but no one knows how well.

"I think that potentially neuraminidase inhibitors may work if you are already on them as prophylaxis (prevention)," Osterholm said. That would mean taking them daily for days or weeks.

"That means that very, very limited supply is going to become a lot more limited."

FIGHTING OVER SCARCE SUPPLIES

The United States has enough courses of Tamiflu to treat about 2.3 million people. The Health and Human Services Department says another 2 million treatment courses are on order and will arrive by the end of the year.

But some 90 million people would need the drug in the event of a flu pandemic, University of Virginia flu expert Dr. Frederick Hayden told a meeting on Saturday.

At current capacity, it would take about 10 years to produce enough oseltamivir to treat 20 percent of the world's population, Hayden said.

"Now people are saying whoever has the most Tamiflu wins," Osterholm said. "I worry so much that Tamiflu is a surrogate for protection."

And vaccines are not an answer yet and will not be for years. There is an experimental vaccine against H5N1 but there are only a few thousand doses of it.

It takes months to make influenza vaccine and H5N1 kills chickens -- the source of the eggs that are needed under current old-fashioned production methods to make flu vaccines.