This was the Big One - a deadly flu epidemic. But fortunately it was a fake.
So when U.S. health officials made some missteps in their largest-ever drill to prepare for a national outbreak of a deadly new flu, no one died.
Some information was wrong because people misstated facts as they passed them on - like a game of telephone gone slightly awry. Some information was classified, so some key public health experts didn't have all the facts.
And there was an ice storm - for real - that hit the Atlanta area and caused the U.S. Centers for Disease Control to stop the exercise early so employees wouldn't be caught in the weather.
Disaster planning has become a common concept in government, but it's relatively new at the CDC. "We haven't had a tradition in public health" of doing such drills, said Glen Nowak, a CDC spokesman.
The drill involved close to 300 CDC employees and was designed to run over a 24-hour period, from Wednesday to Thursday. Most of the action was at CDC's emergency operations center - the agency's equivalent to NASA's Mission Control in Houston.
An Associated Press reporter and three other journalists were allowed to observe - an unusual step for the CDC, but an effort to better work with the media and improve communication should a real pandemic occur.
The drill was designed and run by MPRI, an Atlanta consulting company led by retired military officers. The CDC is paying the company $7 million for its work on the drill, future exercises and some planning work.
It started with CDC Director Dr. Julie Gerberding and her top infectious disease staff meeting Wednesday morning to confront the hypothetical disaster - we repeat, this is a fake scenario:
_ A 22-year-old Georgetown University student who visited his family in Indonesia returned to the United States. He became seriously ill the next day and went to a Washington, D.C. hospital. Lab tests confirmed he had the bird flu that's been killing people in Asia.
In reality, this kind of influenza - scientists call it H5N1 - has not been spread efficiently from person to person. But in the drill, CDC officials got information that it spread among the student's family back in Indonesia and might be a contagion threat here.
More bad news...
_ The student lived in a dormitory, and some of his housemates were reporting flu-like illness.
_ He was a member of the Georgetown swim team and may have infected several members before they went to New York for a swim meet.
_ He was on three different flights on his way from Jakarta to Washington, exposing hundreds of other passengers who scattered to at least 16 U.S. cities. One was a 55-year-old man who had since died in Chicago from a respiratory illness that might be bird-flu related.
_ The student died. Later that day, it became clear that eight people had cases of H5N1, including the Chicago man, and tests on others were pending.
At the time the exercise was cut short, the government was facing some big decisions. One was whether to start shipping from federal stockpiles more than 21 million doses of Tamiflu, and antiviral medication. Should it all go out at once, or just to states that had confirmed cases?
Another was whether to send all flights from Indonesian airports with sick patients only to certain U.S. airports - a measure that could jack up public concern and cause serious economic fallout.
Throughout the day, there were moments of miscommunication. In a late-morning briefing with a consulting company staffer playing the U.S. Secretary of Health and Human Services, Gerberding repeatedly said the student was in Baltimore (not Washington, D.C.). CDC officials at various times said they had passenger manifestos from two of the flights the student had been on, then they seemed to say they had the information on all, then they seemed to backtrack.
Slips were expected in a novel experience like this, but it's important to note that the facts of the case were straight at the crucial points. "We actually had all the correct information at the time decisions were made," said Dr. Stephen Redd, the CDC official who was the flu pandemic expert advising the exercise's incident commander.