Update: On Apr. 16, 2018, Consumer Reports advised against eating romaine lettuce again after an E. coli outbreak sickened 35 people across the U.S.

Update: On Jan. 25, 2018, U.S. food safety and health officials declared an end to the E. coli outbreak linked to leafy greens. In light of this development, Consumer Reports is no longer recommending that consumers avoid romaine lettuce. For more information, read our update.

The Centers for Disease Control and Prevention (CDC) announced today that seven new E. coli infections have been identified, likely associated with contaminated "leafy greens." 

The seven new reports brings the total number of cases involving E. coli 0157:H7 to 66 in the recent outbreak in the U.S. and Canada. Two new states—Maryland and New Jersey—were added to the list of states, now at 15, where infections have been detected.

The CDC said it hasn’t identified the type of leafy green involved and said its investigation is continuing. But Canadian health officials identified Romaine lettuce as the type of leafy green that was the likely culprit in the outbreak in their country.

The CDC previously said that the strain of E. coli involved in the U.S. outbreak was a genetic near-match with the strain that made people sick in Canada. All 66 cases occurred between mid-November and mid-December.

Last week, Consumer Reports advised consumers to avoid romaine lettuce for the time being, until more information was released. Today’s CDC announcement doesn’t change that recommendation.

“It is clear that the E.coli bacteria that made the U.S. victims and the Canadian victims sick are closely related. Canada has identified the source as romaine lettuce,” says Jean Halloran, director of Food Policy Initiatives at Consumers Union, the policy and mobilization division of Consumer Reports. “Right now the CDC is saying it could be other leafy greens, but until we have more corroborating evidence, we continue to think it prudent to avoid romaine lettuce for now.”

The Canadian Public Health Agency today declared the outbreak in that country over and is no longer advising Canadians to avoid romaine lettuce, even though the way the lettuce became contaminated still hasn't been identified.

The CDC says that while it is too soon to declare the outbreak over in the U.S., it is likely that the leafy greens causing the outbreak are no longer in the food supply.  

Consumer Reports' food safety experts think it's key to identify the exact source of the outbreak to increase the chances that future infections can be prevented.

Avoiding Romaine Still The Best Advice

Matt Wise, head of the CDC’s Outbreak Response Team, said the CDC conducted interviews with 13 people who contracted E. coli. All reported eating leafy greens. Of the nine people who provided extra information, five (56%) recalled eating romaine lettuce in the week before they became ill, according to the CDC. Still, Wise says the agency has not been able to conclude with certainty that romaine lettuce was the source.

E. coli 0157:H7 bacteria produces a toxin, making infections potentially dangerous. In addition to the typical vomiting and diarrhea associated with food poisoning, this type of bacteria have the potential to cause hemolytic uremic syndrome, a serious condition affecting the blood vessels that can lead to kidney failure and death.

The recent outbreak has caused one death in California, another in Canada, and at least 22 hospitalizations in the U.S. and Canada.

Federal Agencies Under Pressure

Pressure had been mounting on the CDC and the Food and Drug Administration (FDA) to provide more information to the public about this outbreak.

Rep. Rosa DeLauro (D-CT), who serves on the congressional subcommittees that oversee funding for the CDC and FDA, issued a strongly worded letter this week to Brenda Fitzgerald, director of the CDC. “I continue to be deeply alarmed by the Centers for Disease Control and Prevention’s (CDC) response to the recent multistate outbreak of E. coli. CDC confirmed the outbreak on December 28—almost a month and a half after the first infection,” said DeLauro.

Rep. Louise Slaughter (D-NY), a microbiologist, affirmed DeLauro’s sentiments in a statement to Consumer Reports: “The delay in CDC or FDA providing updated information to consumers is very disappointing...Timely information is critical to avoid potentially contaminated foods and I call on FDA to take all necessary steps to protect public health."

The CDC said that six of the seven new cases occurred within the time frame of all the other reported incidents, between November 15 and December 8. One of the cases occurred more recently, on December 12. Wise noted that any leafy green that was in the food supply at the time of the last reported infection would likely be long gone by now.

However, James E. Rogers, Ph.D., Director of Food Safety Research and Testing at Consumer Reports, cautions that the CDC's position on this could give consumers a false sense of security.

“Without knowing exactly what caused this outbreak, we risk seeing a new batch of tainted product come onto the market,” he said. “For instance, if the equipment at a processing plant is contaminated with E. coli O157:H7, new product could become a source of further infections.”

The CDC’s investigation has not identified a specific type, brand, or producer of romaine or any other leafy greens, which Wise says has made it hard to home in on a source. Some companies (the fast food chain Wendy’s and Compass—the country’s largest food service company) have voluntarily withdrawn all romaine lettuce for the time being, though there is no indication that these companies were connected to the outbreak.

In a tweet this week, Scott Gottlieb, commissioner of the FDA (the agency that would be responsible for issuing any product recall), said that the FDA “will continue to update on the recent E. coli outbreak. Illness onsets among reported cases occurred in late Nov & early Dec, so the source of these cases likely is no longer on the market.  We're working closely with partners to identify that source.”

An FDA spokesperson later confirmed this position to Consumer Reports: “This work is ongoing. We want to make sure consumers have the latest information and when we have information that consumers can use—such as any foods to avoid—we will share it immediately.”

If you do have romaine lettuce already on hand, remember that washing it will not effectively remove E.coli bacteria. Cooking will kill it, but romaine is most often eaten raw.

“I’m thinking the best advice is the broadest here,” says Bill Marler, a Seattle-based attorney specializing in food safety cases. “When in doubt, throw it out.”

CLARIFICATION: An earlier version of this article said more than half of the 13 people sick with E. coli who were interviewed by the Centers for Disease Control and Prevention said they ate Romaine lettuce. This version clarifies that of those 13, only nine provided extra information about what they ate, according to the CDC. Of those nine, five reported eating Romaine lettuce in the week before they became ill.