The CDC believes the E. coli outbreak, which has so far led to 22 hospitalizations and zero deaths, can be traced back to lettuce grown in the Yuma, Ariz., area. Individuals in 11 states, ranging from Connecticut to Washington, have been affected, with the most E. coli cases — nine — reported in Pennsylvania.

No specific grower, supplier, distributor, or brand has been implicated in the outbreak, so no recall has been issued. Still, the CDC is warning consumers to dispose of any previously purchased chopped romaine lettuce, and is urging them to try to determine whether lettuce was grown in the Yuma area before ordering it in restaurants or purchasing it in grocery stores.

E. coli is a bacterial infection typically caused by eating or drinking contaminated food or water, according to the Mayo Clinic. Most strains of E. coli are harmless or cause relatively minor gastrointestinal issues, though more serious infections may result in severe cramping, bloody diarrhea, and vomiting. Children and the elderly are also more likely than healthy adults to develop complications resulting from the infection.