based on clinical findings, the descriptive epidemiology of early cases, and hypothesis generating interviews, investigators hypothesized that the source of the outbreak was a viral pathogen spread by a food or beverage served at the main cafeteria at the university between March 5 and 10. As a result, TDH environmental sanitarians inspected the main cafeteria and interviewed staff on March 12. Thirty-one staff members were employed at the cafeteria of whom 24 (77%) were foodhandlers. Except for one employee who worked at the deli bar and declined to be interviewed, all dining service personnel were interviewed. Question 13: What key areas should be explored during interviews with the cafeteria foodhandlers? ______________________________________________________________________________ Cafeteria staff were questioned about their responsibilities in the cafeteria such as the foods they handled, which meals they served, and where they usually worked (e.g., deli bar, grill). They were also asked about use of gloves, handwashing practices, their work schedule during the week before the outbreak, and if they had been ill at that time. In the cafeteria, the deli bar had its own preparation area and refrigerator. During mealtimes, sandwiches were made to order by a foodhandler. Each day, newly prepared deli meats, cheeses, and condiments were added to partially depleted deli bar items from the day before (i.e., without discarding leftover food items). While the deli was open for service, sandwich ingredients were not kept refrigerated or on ice. The deli bar containers were not routinely cleaned. Samples of leftover food, water, and ice were collected. None of the foodhandlers interviewed reported being ill in the last two weeks. Stool cultures were requested from all cafeteria staff. Before dinner on March 12, the City Health Department closed the deli bar. Question 14: Do you agree with the decision to close the deli bar? What actions would you take now? ______________________________________________________________________________

PART V - DESIGNING AN EPIDEMIOLOGIC STUDY TO TEST THE HYPOTHESIS On the evening of March 12, about 36 hours after the initial call to the health department, TDH staff conducted a matched case-control study among students at the university. Ill students (reported from emergency rooms and the Student Health Center) who could be reached at their dormitory rooms were enrolled as cases. Dormitory roommates who had not become ill were asked to serve as matched control subjects. Investigators inquired about meals the students might have eaten during March 5-10 and where the foods were eaten. All information was collected over the telephone. Question 15: What are the advantages and disadvantages of undertaking a case-control study instead of a cohort study at this point in the investigation? Question 16: How would you define a case for this study? __________________________________________________________________________________ Twenty-nine cases and controls were interviewed over the telephone. Investigators tabulated the most notable results in Table 1. Table 1. Risk factors for illness, matched case-control study, main cafeteria, University X, Texas, March 1998.

Question 17A: How do you interpret these data? Question 17B: What elements of this case-control study might affect the validity of the measured association? _____________________________________________________________________________________ Eating at the main cafeteria, in general, was not associated with illness; however, eating from the deli bar during lunch on March 9 or March 10 was significantly associated with illness. Because such a small number of controls ate at the deli bar, individual food items from the deli bar could not be examined.