CHICAGO -- In a small computer laboratory in downtown Chicago, epidemiologist Colleen Monahan is playing a video game designed to terrify the city's public health workers.
The scenario is grim: Someone has unleashed an unknown biological agent in several skyscrapers. Clouds of noxious gas are billowing in the streets, poisoning the air and seeping into the soil. The millions of sick and dying overwhelm the city's hospitals and clinics.
What happens next? How do workers help the most people and prevent panic from tearing the city apart?
Since the troubled emergency response to Hurricane Katrina, the city has budgeted as much as $500,000 to create video games that will help train about 1,300 public health employees to prepare for a major disaster.
''Everyone wants to avoid a repeat of what happened in New Orleans, so training is clearly a hot topic right now," said Monahan, director of the Center for the Advancement of Distance Education at the University of Illinois at Chicago, which is developing the training exercises for the city. ''Games are a way people can have fun and still be sure they're learning."
The games, paid for by an initiative of the Centers for Disease Control and Prevention, simulate what workers could face in a terrorist attack, natural disaster, or massive medical emergency such as an avian flu pandemic.
The first game, which puts players in the middle of a terrorist attack, is to be rolled out by late January. All public health workers are required to play the game by year's end.
The city project is one of a growing number of efforts nationwide to use games to teach. The military has been a leading proponent of such digital tools, turning to games to recruit new soldiers and train sharpshooters.
The Naval Research Office has helped fund ''Virtual Iraq," which recreates firefights and other combat scenarios in the Middle East. Therapists are using the simulation, developed by Virtually Better Inc. in Decatur, Ga., to help Iraq veterans deal with post-traumatic stress disorder.
Graduate students at Carnegie Mellon University have been working with the New York Fire Department on a game called ''Hazmat: Hotzone" to train emergency workers how to deal with hazardous materials in various situations.
In one scenario, firefighters race through Manhattan to a subway station where a green gas is coming out of a trash can and commuters are having trouble breathing.
Researchers hope to have the game finished by spring 2007. They will offer it free to fire departments across the United States.
Looking at the success of such programs, Chicago public health officials said, they decided in the summer to create the games.
Emergency responders and health workers had been trained with role-playing exercises. But requiring about 1,000 people to physically walk through such drills was costly and time-intensive.
It was also difficult to track the drills' effectiveness, officials said, because there often weren't enough people to watch and judge individual workers' performances.
Chicago's video game is fairly straightforward. Workers can play at least 23 characters, such as medical evaluator or someone dispensing pharmaceuticals.
The game opens with a virtual newscaster warning that a terrorist group has unleashed a deadly agent on the city and that all residents must head to a clinic or polling station to be vaccinated.
Players are inside a triage center facing a growing line of patients. Each patient has a different complaint; it is up to players to decide whether the patient is healthy and should go home or needs treatment. If the player takes too long to decide, the patients grow restless. If the player repeatedly makes the wrong choice, the mood in the center shifts from ''calm" to ''nervous" to ''riot" -- and security must be called.
Staffers at the Center for the Advancement of Distance Education are developing games featuring other catastrophes, including an anthrax outbreak, radiological exposure, and the plague. ''We're concerned with training people to save lives," said Lars Ullberg, the project's executive producer. ''Playing is a natural learning experience. Besides, wouldn't you rather have fun with training?"