McDonald’s officials decided to pull salads from 3,000 of their U.S. restaurants while they work with federal and state investigators to find the specific source of Cyclospora parasites that have infected more than 100 people.

The outbreak of cyclosporiasis linked to the McDonald’s salads is not thought to be related to another ongoing outbreak of the parasitic infections associated with pre-cut vegetable and dip trays marketed under the Del Monte brand, according to federal officials. 

Investigators from the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention reported in recent days that the implicated salads were pulled from McDonald’s restaurants in 14 states.

“Many ill people reported eating salads from McDonald’s restaurants located in the Midwest. People reported eating a variety of McDonald’s salads,” according to the CDC.

A statement from the multi-national fast food chain reported the states where the implicated salad was distributed as Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, Montana, Nebraska, North Dakota, Ohio, South Dakota, West Virginia and Wisconsin.

“McDonald’s has been in contact with public health authorities from Iowa and Illinois about an increase in Cyclospora infections in those states,” according to the McDonald’s statement. “In addition, the CDC also has received reports of people who became sick in Minnesota, Missouri, Nebraska, South Dakota, and Wisconsin who ate salads sold at McDonald’s locations in those states.

“… we voluntarily stopped selling salads at impacted restaurants until we can switch to another lettuce blend supplier.”

As of Friday the CDC was reporting 61 confirmed infections from Cyclospora parasites in people across seven states — Iowa, Illinois, Minnesota, Missouri, Nebraska, South Dakota and Wisconsin. However, Illinois officials have reported 90 confirmed cases in their state alone.

The discrepancy is not unusual, though, especially with Cyclospora. There can be up to six weeks lag time between when a person becomes ill from the parasite and when their confirmed lab tests are reported to federal officials. The CDC says Cyclospora illnesses that began after June 1 likely have not yet been added to the federal case count. 

Illnesses in the parasitic outbreak linked to the McDonald’s salads started on or after May 1. The most recent person known to have been infected became ill on July 10. The sick people range in age from 16 to 79 years old. Two  people have been hospitalized. No deaths have been reported.

To view the full sized graphic about the transmission and life cycle of Cyclospora parasites, please click on the image.

“If you have eaten a salad from a McDonald’s restaurant in Iowa, Illinois, Minnesota, Missouri, Nebraska, South Dakota, or Wisconsin since mid-May — on or after May 14 — and you developed diarrhea, see a healthcare provider to be tested for Cyclospora infection and to be treated if you are sick,” the CDC advised consumers.

“Do not eat leftover salads from McDonald’s restaurants that were purchased in Iowa, Illinois, Minnesota, Missouri, Nebraska, South Dakota, or Wisconsin. Throw them away.”

The FDA reports it has not identified which salad ingredient could be the source of the microscopic Cyclospora parasite. The agency is working with McDonald’s officials to trace all of the salad ingredients back through the supply chain. 

“… multiple components of these salads are under consideration. The investigation is ongoing and the FDA is currently reviewing distribution and supplier information,” according to the agency’s outbreak report.

Anyone who has eaten a McDonald’s salad in any of the 14 states where the salad blend was distributed and developed symptoms of cyclosporiasis should seek medical attention. Specific laboratory tests are needed to diagnose cyclosporiasis, which sometimes mimics symptoms of flu and other illnesses. 

It takes Cyclospora parasites days to weeks after being passed in a person’s bowel movement to become infectious for another person. Therefore, it is unlikely that cyclosporiasis is passed directly from one person to another. It is commonly spread via fresh produce. Washing and rinsing food does not remove or kill the parasite, according to the CDC and FDA.

Some people infected with the parasite do not develop symptoms, but they can infect others.

“Most people infected with Cyclospora develop diarrhea, with frequent, sometimes explosive, bowel movements. Other common symptoms include loss of appetite, weight loss, stomach cramps/pain, bloating, increased gas, nausea, and fatigue. Vomiting, body aches, headache, fever, and other flu-like symptoms may be noted,” according to the FDA notice on the outbreak.

“If not treated, the illness may last from a few days to a month or longer. Symptoms may seem to go away and then return one or more times.”

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