Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention, recognized that prevention might not be possible, but the CDC's goal is to slow the spread as the possible "pandemic virus moves from one border to another."

Experts predict that even a mild pandemic could kill approximately 100,000 to 250,000 Americans -- the most severe could kill 2 million. Top health officials compared that to the 1918 Spanish influenza that caused at least 675,000 U.S. deaths and almost 50 million deaths worldwide.

A pandemic is a globally spread disease that is transmitted from person to person. Chances of a pandemic are heightened when a new type of flu virus emerges that the human body is not immune to. New types of vaccinations must be created to fight against the new strains.

After a spate of headlines last year, the threat of avian influenza nearly disappeared from the news -- the bird-flu virus was "last year's story." Yet its growing presence is prompting concern: "People are very nervous about what's happening in Asia right now, and the odds are not great," said Levi, executive director of the Trust for America's Health. The Infectious Diseases Society of America is calling for an investment of at least $2.8 billion in new vaccines.

Possible emergency action includes closing schools and day care for up to three months, banning people from all public settings and demanding people stay home from work.

Some conference attendees pointed to the obvious economic crises such laws would create, including hardship for low-income workers who do not receive sick-leave benefits. Top health officials announced their goal for emergency health benefits nationwide once a pandemic is declared.

Other concerns: In a nation with millions of single-parent families, who would watch the children when schools and day-care centers close? Without breakfast and lunch programs for needy children, who would ensure the kids are well-fed outside of school?

Temporary medical centers might have staffing problems, Levi said. "Having pop-up hospitals is nice. But then we need pop-up health workers, too."

Though avian influenza has killed fewer than 200 people since 2003, cases continue to turn up in poultry worldwide.

Still, people can fight the yearly hazard of seasonal influenza by receiving annual flu shots, which the CDC strongly suggests. Conference speakers blamed inadequate media coverage for severely underplaying the risks of seasonal flu.

Each year in the United States flu sends more than 200,000 people to the hospital, and 36,000 people die.

Related Links
US Bird Flu News
The science and news of Epidemics on Earth