Of the 84 cases in 19 states, 42 of the patients have been hospitalized, a much higher proportion of hospitalizations than usual from an E. coli outbreak.
The three additional states affected by the outbreak are Colorado, Georgia and South Dakota.
While no deaths have been reported, half the cases required hospitalization. The 16-year-old from rural Sacramento, Calif., had been eating salad every day the week before she got sick.
"What's concerning me at this point is there's an unusually high hospitalization rate", said Bill Marler, a food safety lawyer who is representing Louise Fraser, who is suing Panera Bread. "The chain of distribution that supplied that is ultimately responsible".
"We then began replenishing with products from other regions", he said.
So, unless you know for sure where your romaine lettuce is coming from, avoid the leafy green for now.
"Do not buy or eat romaine lettuce at a grocery store or restaurant unless you can confirm it is not from the Yuma, Arizona, growing region", the federal health officials said.
A spokesperson for Kroger also said their stores in MI are not affected, as all romaine lettuce products are fully stocked and safe to consume.
The CDC and the Food and Drug Administration say the Yuma, Ariz., growing region is the source, but no farm has been identified. This particular strain of E. coli produces a Shiga toxin that causes severe symptoms, such as vomiting and diarrhea, and can also lead to kidney failure. Anyone with these symptoms should see a health provider immediately and report their infection to local departments of health and social services. This takes an average of two to three weeks. Most strains are harmless. "Don't buy it; don't eat it", said Dr. Laura Gieraltowski, of CDC's Foodborne Outbreak Response Team. As bagged lettuce and salad mixes become increasingly popular along with a spike in plant-based diets, the process in which farmers clean salads can actually trap bacteria inside the plants, where washing is of no help.
Government health officials are still trying to determine the source of an E.coli outbreak linked to romaine lettuce.