McDonald's is currently cooperating with health officials to trace the outbreak's origins. The CDC has announced the removal of certain ingredients from their menu in various states, specifically fresh slivered onions and quarter pound beef patties, as they are believed to be the sources of contamination. Investigators from both the CDC and the Food and Drug Administration (FDA) are working together to identify the exact contaminated ingredient and its supply chain, which may affect other businesses as well.

The initial report of this outbreak came on September 27. The affected individuals range from ages 13 to 88, with severe symptoms including bloody diarrhea, stomach cramps, vomiting, and fever, resulting in one victim developing hemolytic uremic syndrome, a condition associated with kidney failure.

E. coli bacteria are typically found in the intestines of humans and animals, and while many strains are harmless, some can lead to serious health complications. As investigations continue, health and food safety regulators have yet to issue formal recalls, leaving consumers to await further guidance on the situation. States reporting cases include Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin, and Wyoming.