Most of those patients reported eating romaine lettuce before they became ill, the agency said, adding, “Individuals reported eating romaine lettuce at home, as well as in prepared salads purchased at grocery stores, restaurants and fast food chains.”
American officials have not yet issued recommendations to avoid any particular product because they are still collecting information on the outbreak. Consumer Reports, the nonprofit advocacy organization, said it was urging shoppers to avoid the lettuce as a precaution.
“Even though we can’t say with 100 percent certainty that romaine lettuce is the cause of the E. coli outbreak in the U.S., a greater degree of caution is appropriate given that lettuce is almost always consumed raw,” James Rogers, the director of Food Safety and Research, said in a post on the group’s website.
The widespread nature of the American outbreak suggests that the cause was not limited to a restaurant or particular area, Dr. Wise said.
“When we see this pattern of illnesses, we certainly would default to thinking that this was a commercially distributed product that was contaminated,” he said.
Symptoms of E. coli infection include fever, abdominal pain, bloody diarrhea, and, less commonly, a syndrome that can lead to kidney failure. In such outbreaks, young and older people and those with weakened immune systems are most likely to have the most severe symptoms.
E. coli, short for Escherichia coli, live in human and animal intestines and can contaminate fruits and vegetables when they come in contact with feces from infected animals, according to the Public Health Agency.
That contamination can happen at any point along the journey from farm to table. Most E. coli strains are harmless to humans.