Quarter Pounders at certain McDonald’s eateries have been blamed for at least 49 illnesses and one fatality across 10 states amid an outbreak of E. coli. The fast food giant ceased sales of the trademark burger in states impacted by the illness, the Centers for Disease Control (CDC) said Tuesday. Most of the people who reported getting sick were linked to locations in Colorado and Nebraska, with others in Oregon, Montana, Wyoming, Utah, Kansas, Wisconsin, Iowa and Missouri. As of Tuesday afternoon, at least 10 people had been hospitalized. One death was reported, according to the CDC. It unclear where the mortality occurred. The agency urges anyone who recently ate a Quarter Pounder and subsequently experienced symptoms including fever, dehydration, prolonged or bloody diarrhea, or “so much vomiting that you cannot keep liquids down” to seek immediate medical attention. Symptoms usually begin to show within three to four days of ingesting the bacteria, according to the CDC. Most people recover without treatment in roughly a week, though children, the elderly and people with weakened immune systems are at a higher risk of getting seriously sick. “McDonald’s stopped using fresh slivered onions and quarter-pound beef patties in several states while the investigation is ongoing to identify the ingredient causing illness,” the CDC said. McDonald’s said it removed Quarter Pounders from its menus in Colorado, Kansas, Utah and Wyoming, as well as parts of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma. New York and surrounding states have not appeared to be impacted by the E. coli breakout. The company said in a statement it’s taking the matter very seriously. “The initial findings from the investigation indicate that a subset of illnesses may be linked to slivered onions used in the Quarter Pounder and sourced by a single supplier that serves three distribution centers,” according to McDonald’s North America Chief Supply Chain Officer Cesar Piña. “As a result, and in line with our safety protocols, all local restaurants have been instructed to remove this product from their supply and we have paused the distribution of all slivered onions in the impacted area.”