Norwalk virus gastroenteritis. An outbreak associated with a cafeteria at a college.

An explosive outbreak of gastrointestinal illness occurred among students and employees at a small college in Florida in November 1980. Common symptoms were diarrhea, nausea, weakness, abdominal cramps, chills, vomiting, and low-grade fever. Cases of illness were identified in 40% of 628 students and 15% of 162 employees who responded to a survey. Among students, there was a sevenfold excess risk associated with eating one or more meals at the campus cafeteria November 3-5 (p much less than 0.001). Tossed salad from one meal was strongly associated with illness (p less than 0.0001). Fecal contamination of the salad was documented, although the source of contamination was not identified. Person-to-person spread could not be demonstrated. Seroconversion to Norwalk antigen occurred in significantly more cases (5/6) than noncases (1/6) (p = 0.04).