The Centers for Disease Control and Prevention is telling consumers to not eat any romaine lettuce, and retailers and restaurants are advised not to sell it.
No brand names have been identified and no recall was ordered.
Officials now say you should throw all types or uses of romaine lettuce away immediately.
The outbreak strain, known as E. coli O157, is more likely than others to cause severe illness.
If you're not sure whether your bagged lettuce includes romaine, chuck it out, the CDC says.
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Six of those people have been hospitalized, and one suffered from hemolytic-uremic syndrome, which is a severe complication that can result from an E. coli infection.
In alarming news for anyone who, say, ate a romaine lettuce salad in the past week: the CDC is warning of a new E. coli contamination. Toss it. In fact, the alert includes advice on how to clean your refrigerator if romaine has been inside it recently.
Talk to your healthcare provider.
Go here for more information from the CDC.
Report your illness to the health department. Some people may develop a fever. "The quick and aggressive steps we're taking today are aimed at making sure we get ahead of this emerging outbreak, to reduce risk to consumers, and to help people protect themselves and their families", Gottlieb added. However, illnesses can start anywhere from 1 to 10 days after exposure.