FDA, CDC, and state partners continue investigating a multistate outbreak of E. coli O157:H7 linked to slivered onions served on Quarter Pounder burgers at McDonald’s restaurants in certain states. As of November 13, 2024, 104 people infected with the outbreak strain of E. coli O157:H7 have been reported from 14 states. Colorado – 30, Montana – 19, Wyoming – 6, Kansas 3, North Carolina 1, Iowa 1, Missouri 8, Michigan 1, Nebraska 12, New Mexico 10, Oregon 1, Utah 8, Washington 1 and Wisconsin 1.
Of 98 people with information available, 34 have been hospitalized, and 4 people developed HUS, a serious condition that can cause kidney failure. One death has been reported from an older adult in Colorado. This person is not one of those who developed HUS. Of the 81 people interviewed, 80 (99%) report eating at McDonald’s. Seventy-five people were able to remember specific menu items they ate at McDonald’s. 63 of 75 people (84%) reported a menu item containing fresh slivered onions.
FDA, Colorado Department of Agriculture (CDA), and Colorado Department of Public Health and Environment (CDPHE) have collected onion and environmental samples from McDonald’s stores, distribution centers, and firms of interest for laboratory analysis. At this time, one FDA sample of recalled onions has tested positive for E. coli, but it is a non-O157:H7 Shiga toxin-producing E. coli (STEC) and does not match the outbreak strain or any other clinical illnesses. Whole genome sequencing (WGS) analysis determined that the sample is positive for E. coli O168:H8 and contains the Shiga toxin gene stx2a. Additional sample results are pending. More information will be provided in this update as it becomes available.
FDA has completed onsite inspections at a Taylor Farms processing center in Colorado and an onion grower of interest in Washington state.
The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for E. coli. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks determine if a sick person is part of an outbreak