The worst case scenario, according to U.S. government planners: Two million dead. Hospitals overwhelmed. Schools closed. Swaths of empty seats at baseball stadiums and houses of worship. An economic recovery snuffed out.
We're nowhere close to that. But government leaders at all levels, and major employers, have spent nearly four years planning for the worst in a series of exercises. Their reports, as well as interviews with policymakers, paint a grim picture of what could happen if the swine flu gets severely out of control.
A full-scale pandemic - like the 1918 Spanish flu - would sicken 90 million Americans, or about 30 percent of the population. It could claim the lives of about 2 percent of those infected, about 2 million people, according to government experts.
To put that in perspective, the regular flu causes about 30,000 deaths each year.
"This may or may not be the killer flu," said Kim Elliott, deputy director of the Trust for America's Health, and independent public health group. "But it certainly does seem to have that potential, because it's a novel virus."
A pandemic moves with explosive speed and comes in successive waves. That's why planners start with the worst case.
If a pandemic strikes, the government estimates that nearly 10 million patients would have to be admitted to the hospital, and nearly 1.5 million would need intensive care. About 750,000 would need the help of mechanical ventilators to keep breathing.
No one would be immune from the consequences, even those who don't get sick, according to worst-case exercises run by local and national agencies.
Schools would be closed to try to block the spread of illness, for example, but school buses might be used to take flu victims to alternative clinics rather than overcrowded hospitals.
A 2006 report on the Washington region found both Maryland and Virginia would run out of hospital beds within two weeks of a moderate outbreak.
People who got sick would be isolated, and their relatives could be quarantined.
But even if families weren't required to stay home, many would do so to take care of sick relatives, or because they were afraid of getting sick themselves.
Hotels, restaurants and airlines would face loss of business as business travel and meetings would be replaced by teleconferences.
In the cities, commuters who do go to work might drive, bike or walk instead of using mass transit. On the subway, people would be asked to wear protective masks.
Movie buffs would avoid theaters and rent DVDs instead.
In 1918, authorities even called on churches to cancel services, to the chagrin of some pastors.
As entire societies turn inwardly, the global economy would take a direct hit.
Trust for America's Health estimated in 2007 that a severe pandemic would shrink U.S. output by about 5.5 percent.
"It could be a real blow to any type of recovery," said Elliott. "The whole idea of a just-in-time economy means we depend on each other globally."
But wait a minute. Catch your breath.
Even if the new swine flu from Mexico turns out to be especially aggressive, the worst consequences could be averted.
The nation has made strides in stockpiling antiviral medicines, speeding the production of vaccines and laying down basic public health guidelines.
The government got serious about worst-case planning during the 2005 bird flu scare, as the lessons of Hurricane Katrina loomed large.
"We have a playbook that was developed and is being followed," said Michael Leavitt, who as secretary of Health and Human Services oversaw pandemic planning for President George W. Bush. "It's a substantially better picture than what we faced three years ago."
There are gaps. Some states have not stockpiled their full allocation of antiviral medicines, critical in treating and preventing diseases during the early stages of a pandemic, before a vaccine has been developed.
And Elliott said the federal government has not fulfilled some elements of its own plan, such as purchasing preventive doses of antivirals that would be reserved for medical personnel and first responders. So far, antiviral medicines are proving effective against the Mexico flu.
Dr. Jeff Runge, former chief medical officer for Homeland Security, said it's clearly not a pandemic yet, but it's too early to tell. The next week or two will be critical.
Runge seemed confident. "We've come a long ways since we've been doing this pandemic flu planning," he said.
On the Net:
U.S. information on swine flu: http://www.pandemicflu.gov
Copyright 2009 The Associated Press.