A new report suggests that contaminated irrigation canals may have played a key role in the recent E. coli outbreak that made fields of romaine lettuce unsafe to eat, killing five people and sickening 210 people across 36 states.

With those numbers, the outbreak in question is now the largest of its kind in a decade — the last large-scale E. coli outbreak occurred in 2006, involving spinach grown in California that investigators tied to a contaminated steam.

The bacteria was traced to romaine lettuce grown in Arizona. Amid the scare, Both the Food and Drug Administration and the Centers for Disease Control and Prevention warned people against consuming the vegetable unless they were sure it didn't come from the aforementioned state.

Romaine Lettuce E. Coli Outbreak Is Over

Even though the outbreak has stopped, the FDA and CDC say investigation will take months. However, in an updated report published Thursday, June 28, they said contaminated canal water is the likely culprit. In their investigation, canal water samples showed presence of E. coli O157:H7, with a similar genetic fingerprint as the outbreak strain. 

Further analysis is still ongoing, with new findings poised to be shared to the public immediately.

"Several environmental samples of canal water in the area have been found to contain E. coli O157:H7 that genetically match the strain of bacteria that caused the outbreak," said FDA commissioner Scott Gottlieb.

Most forms of the E. coli bacteria don't pose any significant threat, but one strain, called O157:H7, can result in severe complications, including stomach cramps, vomiting, diarrhea, and a type of kidney failure called hemolytic uremic syndrome. E. coli is most often associated with animals, however, since it usually thrives in digestive tracts. One way it can get onto crops is by virtue of E. coli-contaminated manure.

"[W]e are continuing our investigation in an effort to learn more about how the outbreak strain could have entered the water and ways that this water could have come into contact with and contaminated romaine lettuce in the region."

FDA, CDC Investigating Other Outbreaks

In addition to the romaine lettuce case, the CDC and FDA are also working on several other recent outbreaks, including reports of salmonella-contaminated pre-cut melons, eggs, and even a cereal from Kellogg's.

People should not worry about these outbreaks, according to Gottlieb. While the frequency is concerning, he said food supply isn't any less safe than it has been previously. What's actually happening is we simply have more ways to better identify these outbreaks because of technological improvements, said Gottlieb.

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