An E. coli outbreak linked to McDonald’s Quarter Pounders has led to at least 49 illnesses across 10 states, including one death. Here’s what we know. Quarter Pounders made people sick The US Centers for Disease Control and Prevention issued a food safety alert Tuesday warning that dozens of people reported eating the Quarter Pounder sandwich at McDonald’s before becoming sick.

Fresh onions are the likely source of an E. coli outbreak at McDonald's restaurants that has sickened 49 people and killed one, the U.S. Department of Agriculture said late on Wednesday, alarming some McDonald's customers and other fast-food chains using onions as an ingredient.

McDonald's says consumers should feel safe eating at its restaurants. Food safety experts say it depends on your capacity for risk.