April 27, 2018 -- Fourteen more people have fallen ill with dangerous E. coli infections that have been traced to romaine lettuce, making this outbreak the largest in over a decade.

New cases were reported in the last few days in Mississippi, Tennessee, and Wisconsin -- three states that had previously been unaffected, according to the CDC.

The most recent illness started on April 20.

So far, 98 people from 22 states have been sickened in the outbreak, including 10 who developed a life-threatening type of kidney failure called hemolytic uremic syndrome. No deaths have been reported.

In a press briefing Friday, investigators from the CDC and FDA warned consumers to continue to be careful when eating romaine lettuce.

Though the growing season in Yuma, AZ, the apparent source of the outbreak, is over, experts said they couldn’t be sure the threat had passed.

“The most important thing for people to do is to avoid eating any romaine lettuce unless they can confirm that it wasn’t grown in the Yuma, AZ, growing region,” said Matthew Wise, PhD, deputy branch chief for outbreak response at the CDC.

“When in doubt, don’t buy it or don’t eat it,” he said.

This E. coli outbreak is now the largest since 2006, when more than 200 people fell ill after eating contaminated spinach.

Investigators say the bacteria that are making people sick are especially aggressive because they produce a kind of toxin called Shiga toxin 2, or Stx2.

The toxin binds tightly to the cells that line the insides of blood vessels, and ultimately “destroys the lining of the blood vessel,” says Robert Tauxe, MD, director of the division of Foodborne, Waterborne, and Environmental Diseases at the CDC.

Some people get kidney failure when it interrupts the blood supply to the kidney, Tauxe said. Many people get bloody diarrhea when the toxin attacks their stomach and intestines. The infection can also cause strokes when it interrupts the blood supply to the brain.

A typical E. coli outbreak sends about a third of victims to the hospital. In this outbreak, half of people infected have needed hospital care.

So far, investigators have identified one farm, Harrison Farms in Yuma, AZ, that was the source of eight cases of illness that occurred at a prison in Alaska. There, inmates were served lettuce from whole heads of romaine grown on the farm.

“This farm is not currently growing any lettuce,” said Stic Harris, DVM, director of the FDA’s Coordinated Outbreak Response and Evaluation Network.

All of the lettuce grown on the farm was harvested between March 5 and March 16 . Because that lettuce is now past its 21-day shelf life, investigators say a recall isn’t possible.

Because other illnesses have been tied to bagged, chopped lettuce, investigators say this one farm doesn’t explain the full extent of the outbreak.

“Most of the illnesses in this national outbreak are not linked to the romaine lettuce from this particular farm. We’re investigating dozens of other fields as potential sources of the chopped romaine lettuce and will continue to share information as it becomes available,” Harris said.

E. coli bacteria are often spread through the poop of animals like cows, sheep, goats, and deer.

In the 2006 outbreak, investigators found that cattle from a neighboring farm were free to wander into a stream that irrigated fields where spinach was growing.

Investigators say they will be looking for similar points of contamination in this outbreak.

This is the second time in weeks that tainted romaine lettuce has been linked to E. coli infections. In late December, E. coli infections in Canada and the U.S. were linked to romaine lettuce, but investigators couldn’t ultimately determine the source of the contamination.

The FDA says this new outbreak is not related to the earlier one.

Show Sources

Press briefing, FDA and CDC, April 27, 2018.

Matthew Wise, PhD, deputy branch chief for outbreak response, CDC.

Robert Tauxe, MD, director, division of Foodborne, Waterborne, and Environmental Diseases, CDC.

Stic Harris, DVM, director, Coordinated Outbreak Response and Evaluation Network, FDA.

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