At least 75 people fell ill from the bacterial infection and one person died in Colorado from the O157:H7 strain of E. coli, the Centers for Disease Control and Prevention said Friday. McDonald’s attributed the illnesses to slivered onions, and the Food and Drug Administration indicated that onions might have been the source of the outbreak.

E. coli: Symptoms typically start three to four days after consuming contaminated food or water. The Shiga toxin-producing form of E. coli, the strain identified in the McDonald’s outbreak, causes severe stomach cramps, diarrhea that’s often bloody, and vomiting. People can develop serious kidney issues that require hospitalization.

The CDC said 22 people have been hospitalized from the E. coli outbreak linked to McDonald's Quarter Pounder hamburgers.