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Parasite infections top 500; source questions linger

The cyclospora parasite in human stool has made about 250 people sick in the Midwest.
Bagged salad has been named as the source of a cyclospora food poisoning outbreak in two states, but the rest remain a mystery.CDC

The case count has topped 500 in an ongoing outbreak of parasite-borne food poisoning, but government health officials still have not identified what’s making people sick in all of the 16 affected states.

Last week, the Food and Drug administration confirmed that bagged mixed salad made by a Mexican division of Salinas, Calif., produce supplier Taylor Farms was behind cyclospora infections in Iowa and Nebraska, which have sickened nearly 240 people in those two states.

Commercial packs of salad mix sold at Olive Garden and Red Lobster restaurants in those states were identified as the culprit, the FDA said. Bruce Taylor, the chief executive for Taylor Farms, told NBC News that the salad mix containing lettuce, carrots and red cabbage came from Mexico.

“All components were grown in Mexico by contract growers adhering to Taylor Farms de Mexico strict food safety protocols,” Taylor wrote in an email.

But neither FDA nor Centers for Disease Control and Prevention officials have said what’s behind the still-growing outbreak in Texas, where some 204 people have been sickened. Officials with Darden restaurants, which operate Olive Garden and Red Lobster, said that Taylor Farms doesn’t supply their produce in Texas.

And federal officials still haven’t determined whether it’s all one outbreak, or whether it’s a series of outbreaks, that have collectively sickened 504 people and hospitalized at least 30.

“CDC and its public health partners are vigorously working to determine if the conclusion reached in Iowa and Nebraska helps explain the increased cases of cyclosporasis in other states,” the CDC website said. “We will update the public on the progress of the national investigation as information becomes available.”

CDC director Dr. Thomas Frieden told CBS news that the agency doesn’t know if all the cyclospora parasites are the same and that the lack of ability to sequence the genome of the organism is costing time.

“Not being able to analyze the genomic sequence in real time is like not being able to solve a crime without fingerprints,” he said.

But food safety experts say that state and federal health agencies have mishandled the investigation, leaving the public still unsure what products may make them sick.

“We all recognize that this outbreak has gone on for far too long without sufficient answers,” said Dr. Michael Osterholm, a former Minnesota state epidemiologist and director of the Center for Infectious Disease Research and Policy, or CIDRAP, at the University of Minnesota.

Osterholm said CDC still hasn’t organized a case-control study, in which epidemiologists contact people who are sick and also healthy people to review what they’ve eaten recently, potentially pinpointing specific foods linked to illness.

Dr. Rob Tauxe, deputy director of the CDC’s division of foodborne, waterborne and environmental illnesses, said the agency is working many angles to track the rare parasite.

Case-control studies can pin-point a particular food item, but so can tracebacks of likely food sources from settings where exposure occurred. In big, multi-state outbreaks, often it is a combination, he said.

“In general outbreaks get solved using a mix of information,” he told NBC News in an email.

Meanwhile, several consumers nationwide have sued Darden Corp. and others, saying that they contracted cyclospora infections after eating tainted salad. Justin Haren, 35, of Toledo, Ohio, filed a suit in that state this week alleging that he became ill after eating at an Olive Garden restaurant on May 28. He wound up in an emergency department a month later and tests confirmed he had cyclosporosis, according to Simon & Luke, the Houston food safety law firm that represents him. 

Most of the illnesses in the outbreak were reported from mid-June through early July, with the number of new cases falling significantly, the CDC website indicates. 

States where cyclospora infections have been reported include Arkansas, Connecticut, Florida, Georgia, Iowa, Illinois, Kansas, Louisiana, Minnesota, Missouri, Nebraska, New Jersey, New York (including New York City), Ohio, Texas and Wisconsin.

Cyclospora is a rare parasite transmitted by human feces, typically through contaminated produce or water. It can cause a range of distressing symptoms, typically including prolonged and intense diarrhea. It can be successfully treated with common antibiotics.

JoNel Aleccia is a senior health reporter with NBC News. Reach her on Twitter at @JoNel_Aleccia or send her an email.