Closing schools, restricting travel and rationing scarce medications may be the nation's first protections if a powerful new flu strain spurs a worldwide outbreak because it will take months to brew a vaccine, say government preparations for the next pandemic.

Specialists say it's only a matter of time before the next one strikes, and concern is rising that the recurring bird flu (search) in Asia could be the trigger since it is mutating in a way that lets it spread easily among people.

There have been three flu pandemics in the last century, the worst in 1918, which killed more than half a million Americans and 20 million people worldwide.

It's impossible to predict the toll of the next one. But estimates suggest a bad one could kill up to 207,000 Americans, says the nation's new response plan, obtained Wednesday by The Associated Press.

That's almost six times more lives than regular flu claims every year. Millions of sick patients could swarm doctors' offices and hospitals, and the country could suffer an economic and social wallop from disruption of transportation, commerce, even routine public safety.

The Pandemic Influenza Response and Preparedness Plan (search), to be released Thursday by the Department of Health and Human Services (search), stresses ways to speed up vaccine production, limit the spread of such a super-flu, and care for the ill.

It's just a first draft, open for public comment through October as the government struggles to decide exactly how to respond to the earliest signs of a pandemic.

"We recognize that we need more treatments and we need more vaccine capability," Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention (search), said in an interview.