Clayton: Do you need a work permit? Megalis Tablet The Nebraska Department of Health announced Tuesday that a prepackaged salad mix was the source of the stomach bug that had sickened 78 Nebraskans since mid-June. The Iowa Department of Health said the same, tracing the diarrhea-causing parasite contracted by at least 143 Iowans to a mixture of iceberg and romaine lettuce, carrots and red cabbage.