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A CDC investigation into an E. coli outbreak linked to Wendy’s has ended without identifying the mystery ingredient that made 109 people sick and sent 52 to the hospital, the agency said.

The outbreak, which began in July and spread to six states including New York and Pennsylvania, originally focused on the romaine lettuce Wendy’s uses in its sandwiches. 

Many of the victims “ate burgers and sandwiches with romaine lettuce, but the specific ingredient that caused the outbreak could not be confirmed,” the Centers for Disease Control and Prevention wrote on its website on Tuesday, announcing that the investigation had ended.

According to the FDA, 13 customers experienced acute kidney failure. A number of them have sued Wendy’s.

One law firm alone, Marler Clark, is representing 40 people who became sick after at Wendy’s during the outbreak.

Wendy’s issued a statement during the investigation explaining that it’s “fully cooperating with public health authorities.”


  The investigation originally focused on the lettuce Wendy’s uses in its sandwiches. Tribune News Service via Getty I The investigation originally focused on the lettuce Wendy’s uses in its sandwiches. Tribune News Service via Getty I

“While the CDC has not yet confirmed a specific food as the source of that outbreak, we have taken the precaution of removing the sandwich lettuce at some restaurants,” Wendy’s said at the time. “The lettuce that we use in our salads is different, and is not affected by this action. As a company, we are committed to upholding our high standards of food safety and quality.”

It has not updated its statement since the investigation ended.


  Wendy’s says the lettuce it uses in its sandwiches is different from the lettuce it uses in its salads. SOPA Images/LightRocket via Gett Wendy’s says the lettuce it uses in its sandwiches is different from the lettuce it uses in its salads. SOPA Images/LightRocket via Gett

It’s the second high-profile, food-borne illness investigation to end recently without identifying what made hundreds of people ill.

A monthslong investigation by the Food and Drug Administration into Lucky Charms breakfast cereal, which made thousands of people ill giving them severe diarrhea, ended in early September without identifying the ingredient that caused the outbreak even as people continue to get sick.

The FDA did not say why the investigation ended, but food safety experts said it’s likely because the pace of new illnesses had slowed down dramatically. 

More than 8,000 customers who ate Lucky Charms posted reports about their bouts with diarrhea on iwaspoisoned.com.

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