In June, health department officials received reports of a cluster of cases with gastrointestinal illness. The first four reported cases had eaten at the same New Haven, Connecticut, restaurant between June 24 and 25. Stool samples showed all four had been infected with Cyclospora. Additional cases were identified when all positive Cyclospora cases were reported to the state health department. A case-control study found significant risk associated with dining at one restaurant, and specifically with the consumption of both the bruschetta and the house salad. Red onions were used in both dishes, but the same cutting board was used for many vegetables and herbs making cross-contamination possible. Based on past outbreaks, the health department workers thought fresh basil could be the contaminated food and requested the Food and Drug Administration do a traceback. The traceback found neither a source of contamination, nor the origin of the basil.