Prepackaged salads sicken more than 170 people in Iowa and Nebraska

Prepackaged salad mix gave at least 178 people in Iowa and Nebraska cyclospora — a rare parasite that causes a lingering gastrointestinal illness — earlier this summer, health officials for the two states said.

A spokeswoman for the Nebraska Department of Health and Human Services said the agency was still trying to identify the specific brand or brands that sold the contaminated mix, which included iceberg and romaine lettuce, red cabbage and carrots.

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Pinpointing the culprit is challenging because by the time the reason for the illness was identified, most of the contaminated salads were no longer stocked in stores, Iowa officials told NBC News.

That also means Iowans looking for an excuse to quit their diet are out of luck. "Iowans should continue eating salads as the implicated prepackaged mix is no longer in the state's food supply chain," Steven Mandernach, chief of the Food and Consumer Safety Bureau of the Iowa Department of Inspections and Appeals told NBC.

Cyclospora causes diarrhea and other flu-like symptoms, which usually develop a week or more after eating food contaminated by the parasite. Cyclospora is typically spread by feces in contaminated food or water.

In total, 373 cases of cyclospora infection have been reported in 15 states since June, sending at least 21 people to the hospital.

The Centers for Disease Control said that it does not yet know whether all cases share the same cause.

"CDC is still actively pursuing all leads and hasn't implicated any single food item as the cause of the outbreak in all states," CDC spokeswoman Sharon Hoskins told the Associated Press. "We're still not sure if the cases in all of the states are linked to the same outbreak."