So far, 17 people in 13 states have been diagnosed with E. coli 0157-H7.
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One American has died.
"This is a particularly nasty type of E. coli," said Consumer Reports Health Expert Jean Halloran.
Dozens of others have also been sickened in Canada.
RELATED: 1 dead, dozens sickened after romaine lettuce E. coli outbreak in U.S.
Canadian health authorities have identified romaine lettuce as the source of the outbreak.
"The CDC and FDA are investigating and they say they haven't nailed it down," Halloran added.
For now, Consumer Reports wants everyone to get rid of their romaine lettuce. Washing it is not enough.
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Halloran says its the first time Consumer Reports has issued a warning before the FDA and CDC. "This is unusual. We've never been in this situation before that a foreign government that we share a food supply with has warned its citizens and the U.S. government is not doing it."
At Falletti Foods, some customers had second thoughts about their salad selection.
"I'm going to put this one back I think," said Joe O'Brien of San Francisco. He was warned about buying romaine. "I got a text from my girlfriend's mom saying, 'don't get romaine lettuce.' I wasn't planning on it, but uh, I guess I won't be eating caesar salad tonight."
Consumer Reports says all other types of lettuce should be safe.
Click here for more information about the E. coli outbreak.
Click here for a look back at recent recalls.