Q&A: Tracking the source of stomach bug outbreak

In this image provided by the Centers for Disease Control and Prevention, a photomicrograph of a fresh stool sample, which had been prepared using a 10% formalin solution, and stained with modified acid-fast stain, reveals the presence of four Cyclospora cayetanensis oocysts in the field of view. Iowa and Nebraska health officials said Tuesday, July 30, 2013, that a prepackaged salad mix is the source of a cyclospora outbreak that sickened more than 178 people in both states. Cyclospora is a rare parasite that causes a lengthy gastrointestinal illness. (AP Photo/Centerd for Disease Control and Prevention)WASHINGTON (AP) — State and federal investigators are trying to figure out the source of a stomach bug that has sickened 372 people in 15 states. Iowa and Nebraska have linked some cases in their states to eating pre-packaged salad mix, but the federal Centers for Disease Control and Prevention and the Food and Drug Administration have said the mix is not linked to all of the cases.