The E. coli outbreak from romaine lettuce is finally over

In an unusually broad warning in November, the Centers for Disease Control and Prevention issued stark guidance against eating romaine lettuce. The agency warned that no one in the United States should eat romaine, due to a recent outbreak of the bacteria E. coli believed to be linked to its consumption. And the agency advised that people and restaurants should throw away all romaine lettuce, regardless of whether anyone has been sickened, and sanitize the areas in which it was stored.

It was a such a severe blanket warning because the CDC and the Food and Drug Administration couldn’t pinpoint a single producer of romaine as ground zero for the outbreak.

But on Wednesday, the CDC announced that the outbreak finally appeared to be over.

Diseases detectives at the agencies along with state partners were able to narrow down the outbreak to an agricultural water reservoir on an Adam Bros, Inc. farm in Santa Barbara County. “FDA is continuing to investigate to learn more about how the E. coli bacteria could have entered the agricultural water reservoir and ways romaine lettuce from the farm could have been contaminated, and whether there are other sources of the outbreak,” the CDC said.

When the CDC issued its warning in November, 32 people in 11 states had been sickened. As of January 9, that number was up to 62 cases in 16 states and the District of Columbia. Symptoms of an E. coli infection typically appear three to four days after exposure and can vary, but often include severe stomach cramps, diarrhea (often bloody), and vomiting. There have been no reported deaths so far.

It also appears the contaminated lettuce has infected people in Canada. Canadian health officials have reported 29 cases of E. coli linked to the current outbreak in four provinces: Ontario, Quebec, New Brunswick, and British Columbia.

This was not the first outbreak of E. coli from romaine lettuce in the US in 2018. An outbreak that lasted four months (March through June) sickened 210 people and killed five; 96 people were hospitalized. The CDC was able to trace the outbreak back to a romaine producer in Yuma, Arizona. It’s likely that the lettuce was contaminated by an infected water source nearby.

In the wake of the latest outbreak, the main players in the lettuce industry have agreed to add labels to their products, telling consumers where and when it was grown, Politico reports. That will help consumers avoid potentially unsafe food from particular regions while still being able to purchase greens.

How does lettuce become contaminated with bacteria? As Vox’s Julia Belluz explained earlier this year:

Instead of buying heads of lettuce that we wash and chop or rip up ourselves, over the past couple of decades, sales of precut and bagged greens have boomed. These mixed greens wind up in our fridges or at restaurants already washed and ready to toss in a salad bowl. But during processing, bacteria living among the leafy greens have a moist environment in which to flourish.

“When you bag and chop [salad], bacteria just gets amplified — and when you ship it across the country, the bacteria has a chance to grow in the bag,” Bill Marler, one of America’s leading food safety attorneys who is representing families affected by [the spring] outbreak, told Vox after the outbreak was first declared.

What’s more, it can be hard to track an outbreak to a single source. “Different lettuces grown at different farms get mixed into bags that are distributed at supermarkets and restaurants all over the country, so food safety officials need to search for the common link among suppliers,” Belluz writes.