Seventeen illnesses have been reported in 13 states, including three cases in California, the CDC said. So far, five people have been hospitalized in the U.S., and one has died.
The illnesses started between Nov. 15 and Dec. 8, 2017, according to the CDC.
In Canada, 41 cases have been reported, and one person has died.
Consumer Reports says people should stop eating romaine lettuce until the cause of the outbreak is identified and the tainted product is removed from store shelves.
Click here for more information about the E. coli outbreak.