A high school reported an outbreak of gastrointestinal illness involving students and staff. Stool samples collected from some of the ill cases showed the presence of Norovirus. A case-control study indicated the school lunch lettuce was the likely source of the outbreak, but no lettuce samples were available for testing. An environmental inspection of the school kitchen reported bare-hand contact with the lettuce by the cooks. It also found one of the cooks had been ill with a gastrointestinal illness one day before working. This individual also reported chopping the lettuce with bare hands. Norovirus can be transmitted up to 48 hours after symptoms stop.