A foodborne parasite outbreak linked to shredded iceberg lettuce has become the largest cyclospora outbreak on record in the United States. The U.S. Centers for Disease Control and Prevention has expanded the investigation to 15 states, adding Arkansas, Iowa, Missouri, Nebraska, New Hampshire and North Carolina after illnesses were traced to lettuce imported from central Mexico. Health officials are continuing to track the outbreak as they work to identify additional cases and prevent further infections. Sometimes the biggest food safety risks begin with something as ordinary as a salad.