Food safety detectives are zeroing in on source of romaine lettuce E. coli outbreak

In an unusually broad warning, the Centers for Disease Control and Prevention in November 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.

Now, the agencies have been able to narrow down the outbreak to romaine lettuce grown in just a few California counties — Monterey, San Benito, and Santa Barbara — in the Central Coast region. All other romaine appears to be safe to eat. “If you do not know where the romaine is from, do not eat it,” the CDC still warns. “If the romaine lettuce is not labeled with a harvest growing region and county, do not buy, serve, sell, or eat it.”

The FDA has found evidence that the E. coli strain responsible for this outbreak came from an irrigation system used by a single farm (Adam Bros. Farms) in Santa Barbara County. But, the FDA adds, “the finding on this farm doesn’t explain all illnesses. … additional romaine lettuce shipped from other farms could also likely be implicated in the outbreak.” So more detective work still needs to be done to find all the farms implicated in this region.

In the meantimes, Adams Bros. farms has recalled its products, including red leaf lettuce, green leaf lettuce, and cauliflower that were harvested between November 27 through November 30. (Read more about the recall from the FDA here).

When the CDC issued its warning in November, 32 people in 11 states had been sickened. As of December 18, that number is up to 59 cases in 15 states. 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 28 cases of E. coli linked to the current outbreak in four provinces: Ontario, Quebec, New Brunswick, and British Columbia.

This is not the first outbreak of E. coli from romaine lettuce in the US this year. 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:

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.

For now, the warning against eating romaine grown in the three California counties is still in place. And it still may be difficult for consumers to know where their lettuce was grown. So when in doubt, throw it out.