CHICAGO (AP) -- A national bioterrorism drill mirrored real life Tuesday as coughing, sneezing patients trooped into Chicago-area emergency rooms acting out symptoms of a mystery SARS-like illness.

Mock patients were fitted with surgical masks and whisked away on gurneys and in wheelchairs as part of the five-day drill that began Monday in Seattle with the simulated detonation of a radioactive "dirty bomb."

"We've never experienced a bioterrorism attack here in Chicago, and I really wouldn't know what to do without having some sort of practice," said Teresa Chou, manager of infection control at Advocate Illinois Masonic Medical Center.

The drill, aimed at testing the readiness of local, state and federal authorities, is the nation's first large-scale counterterrorism exercise since the terrorist attacks on Sept. 11, 2001.

The exercises are being headed by the Homeland Security Department. They will cost about $16 million and involve more than 8,500 people from 100 federal, state and local agencies, the Red Cross and the Canadian government.

According to the drill's script, the same mock terrorist group responsible for the Seattle explosion also release a deadly plague in Chicago. Patients showing up at area hospitals Tuesday gave health officials their first clue that terrorism might be behind the outbreak.

About 160 hospitals in Illinois participated in the drill. Some received live "patients"; others were informed by fax of mock patients and their symptoms.

Illinois Masonic enacted its emergency plan about an hour after the first live patients arrived, with nurses and doctors scurrying to turn the lobby into a triage area. The hospital called in extra staff this week to ensure that real patients would not be affected by the drill.

"No matter how much you plan ahead, how much you do on paper, until you really put (an emergency plan) to the test and stress the system with a large number of victims, you're not going to be able to find the weaknesses," said Dr. Richard Fantus, director of trauma services.

By late afternoon, the Federal Emergency Management Agency was reporting that 14 of the fictional patients had died and another 145 to 160 were exhibiting the flu-like symptoms associated with the outbreak.

According to the script, authorities will need a few days to connect the events in Chicago and Seattle. By week's end, officials are supposed to have traced the Chicago illnesses to the release of pneumonic plague.

As the drill unfolded Tuesday, representatives of various agencies - including Homeland Security, the FBI and federal Centers for Disease Control and Prevention - manned phones at a regional operations center and reacted to new information.

In Seattle's scenario, 150 people were "injured" by the explosion Monday, and 92 were taken to hospitals. Rescuers sought 20 people believed to have been buried in the rubble created by the blast and two were reported killed.

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