Illnesses have been reported in Indiana, Michigan, Ohio, Pennsylvania, and — most recently — Kentucky and New York. No specific food has been officially named the source of the outbreak, but many of the sick people reported eating romaine lettuce on sandwiches from Wendy’s prior to their illness. As a precaution while the Centers for Disease Control and Prevention (CDC) continues to investigate the outbreak, Wendy’s has stopped using romaine lettuce on sandwiches. Wendy’s salads already use a different source of romaine lettuce. As of now, the CDC is not advising consumers to stop eating at Wendy’s because the chain has removed the potentially contaminated product from their stores. It’s also safe to continue purchasing romaine lettuce because the outbreak is not connected to grocery store lettuce or romaine used in other restaurants. “We are fully cooperating with public health authorities on their ongoing investigation of the targeted E. coli outbreak reported in certain states,” Wendy’s said in a statement.

What Is E. Coli?

E. coli is a class of bacteria that is primarily found in the environments and intestines of animals and people. There are many strains of E. coli, many of which are harmless, but some strains can cause sickness ranging from urinary tract infections to pneumonia to diarrhea. Romaine lettuce and other produce become contaminated with E. coli when the bacteria infiltrates irrigation water used in farming. E. coli cannot be reliably washed off the produce once tainted.

How Do I Know if I Have E. Coli?

E. coli symptoms generally occur three to four days after infection and most people recover within a week. Severe E. coli symptoms include:

Diarrhea that lasts for more than three daysBloody diarrheaVomiting so much that you can’t keep liquids downA fever of 102 degrees F or higherDehydration (dizziness when standing up, infrequent urination, dry mouth)

If you have these severe E. coli symptoms, talk to your healthcare provider immediately and report your symptoms to your local health department. Writing down everything you ate in the past week if you feel sick can also help public health professionals solve this outbreak and keep you safe.