"A new U.S. military health surveillance network caught an outbreak of diarrhea at a Marine facility before doctors there were even aware of it, and could detect both sneak bioterror attacks and natural epidemics, one of the organizers said on Saturday.

"The network is still small but has been expanded since last year's Sept. 11 attacks and could serve as the basis for a nationwide early warning system, according to Maj. Michael Lewis, a U.S. Army medical doctor.

"'Dr. Pavlin called out there and said 'You have a problem with diarrhea',' Lewis told a seminar sponsored by the American Medical Association. "They said, 'No we don't -- go away'.'

"This went on for three days until finally the doctors at the depot recognized the outbreak. 'They asked us 'How did you know?'' Lewis said. 'In this case we knew about it before the people on the ground did.'

"Pavlin said the diarrhea turned out to have been caused by Norwalk-type virus, a common cause. It caught similar outbreaks at military facilities in New Jersey, at Fort Knox, Kentucky and at Maryland's Aberdeen Proving Grounds."