The chief topics of discussion one midsummer afternoon in a conference room at the Centers for Disease Control and Prevention (CDC) are ground beef, eggs, salad, almonds, and cilantro. This is no conversation about the lunch menu but a review of outbreaks nationwide of disease caused by food. At the table are 26 epidemiologists—medical detectives charged with investigating the mysterious links between contaminated food and the illness it causes.

The stories are not those I expect to hear, of people getting sick from drinking unpasteurized milk or eating deviled eggs left too long in the hot sun at a picnic, but tales of people sickened by contaminated parsley and scallions, cantaloupes, leaf lettuce, sprouts, orange juice, and almonds; refrigerated potato salad,