Transmission of norwalk virus during a football game.

Background: During a college football game in Florida, diarrhea and vomitin g developed in many of the members of a North Carolina team. The next day, similar symptoms developed in some of the players on the opposing team. Methods: We interviewed those who ate the five meals served to the North Ca rolina team before the game and some of the players on the opposing team wh o became ill. Patients with primary cases were members or staff of the team who had vomiting or diarrhea at least 10 hours after but no more than 50 h ours after eating a box lunch served the day before the game. Patients with secondary cases had a later onset of symptoms or had symptoms without havi ng eaten the box lunch. Stool samples were examined by electron microscopy and by a reverse-transcription-polymerase-chain-reaction (RT-PCR) assay. Results: The two football teams shared no food or beverages and had no cont act off the playing field. Of five meals served to the North Carolina team before the game, only the box lunch was associated with a significant risk of illness (relative risk of illness, 4.1; 95 percent confidence interval, 1.6 to 10.0). The rate of attack among those who ate the box lunch was 62 p ercent. There were 11 secondary cases among the members and staff of the No rth Carolina team and 11 such cases among the Florida players. All four sto ol samples obtained from North Carolina patients were positive for Norwalk- like virus on electron microscopy. All four samples as well as one of two s tool samples from players on the Florida team were positive for a Norwalk-l ike virus of genogroup I on RT-PCR assay; the RT-PCR products had identical sequences. Conclusions: This investigation documents person-to-person transmission of Norwalk virus among players during a football game. Persons with acute gast roenteritis should be excluded from playing contact sports.