preparedness plans in place...,

WaPo | The Bush administration implemented an $8 billion pandemic flu planning program that created a detailed national blueprint and funneled millions of dollars to state and local governments to create and rehearse their own plans.

After the 2003 outbreak of severe acute respiratory syndrome (SARS), the World Health Organization instituted measures that heightened the world's ability to identify and respond swiftly to outbreaks. They included international regulations that call for countries to report worrisome outbreaks quickly and a revised pandemic threat alert system, which was ratcheted up quickly last week.

So when reports emerged from Mexico of a new virus that most people might have no immunity against, and that appeared to be spreading easily from person to person and -- in an eerie echo of 1918 -- was killing healthy young adults, the world went on high alert.

"If what was being reported in Mexico played out in the United States and elsewhere, this was a potentially serious epidemic that was getting underway," Inglesby said. "We had to respond quickly."

The reaction has also been influenced by political missteps in previous emergencies, including the mixed messages and poor communication about the 2001 anthrax letters and the slow reaction to Hurricane Katrina in 2005.

AP | "If we do move into a pandemic, then our expectation is that we will see a large number of people infected worldwide," Fukuda said. "If you look at past pandemics, it would be a reasonable estimate to say perhaps a third of the world's population would get infected with this virus."

With the current total population of more than 6 billion, that would mean an infection total of 2 billion, he said, but added that the world has changed since pandemics of earlier generations, and experts are unable to predict if the impact will be greater or smaller.