Cyclospora is a rare parasite that causes a lengthy gastrointestinal illness. Outbreaks of the same illness have been reported elsewhere in the U.S., but the Centers for Disease Control and Prevention said not all of those can be linked to prepackaged salad mix.
Nebraska officials said the salad mix included iceberg and romaine lettuce, along with red cabbage and carrots, and came through national distribution chains. A spokeswoman for the Nebraska Department of Health and Human Services said the agency was still trying to identify the specific brand or brands.
Local health departments are working with the U.S. Food and Drug Administration to identify exactly where the contamination originated in the food production chain and where the product was distributed.
The Centers for Disease Control says 372 cases of the cyclospora infection, which causes diarrhea and other flu-like symptoms, have been reported in 15 states: Iowa, Texas, Nebraska, Florida, Wisconsin, Illinois, New York, Georgia, Missouri, Arkansas, Connecticut, Kansas, Minnesota, New Jersey and Ohio.
The CDC said at least 21 people have been hospitalized and most of the reported illnesses occurred from mid-June to early July. The CDC and the Food and Drug Administration are investigating the cyclospora infections but have not yet pointed to a source.
"CDC is still actively pursuing all leads and hasn't implicated any single food item as the cause of the outbreak in all states," said CDC spokeswoman Sharon Hoskins. "We're still not sure if the cases in all of the states are linked to the same outbreak."
Hoskins said that in some previous outbreaks of cyclospora, the cause was never discovered
The FDA said Tuesday that it is following Iowa's lead on the salad mix but is following other leads as well. An agency statement said investigators are trying to trace the paths of the food eaten by those who fell ill. That process is "labor intensive and painstaking work, requiring the collection, review and analysis of hundreds and at times thousands of invoices and shipping documents," the FDA said.
The agency said it has a seven person team in its Maryland headquarters and specialists in 10 field offices across the country working to identify the source of the outbreak.
Cyclospora illnesses are spread when people ingest foods or water contaminated with feces. The illnesses are most often found in tropical or subtropical countries and have been linked to imported fresh fruits and vegetables in the past.
Jalonick contributed from Washington, D.C.
Copyright 2013 The Associated Press.