A 10-state E. coli outbreak linked to McDonald’s Quarter Pounder burgers has killed one person in Colorado and sickened at least 26 others in the state, the Centers for Disease Control and Prevention announced Tuesday.

The CDC reported that 49 people nationwide have become ill and 10 people required hospital care, including one child who had serious kidney complications. All of the sick people reported eating at McDonald’s, and “most” said they ate Quarter Pounders, the federal health agency said.

The Colorado Department of Public Health and Environment said the deceased person was “older” and had underlying health conditions, but did not identify the victim.

Neither state nor federal officials specified which McDonald’s restaurants in Colorado served the people sick with E. coli.

People over 65 and children under five are at greater risk of serious illness from E. coli, a type of bacteria that causes vomiting, severe stomach cramps and diarrhea, often with blood. Most people recover without treatment, but some develop severe dehydration or kidney damage.

In addition to Colorado, McDonald’s diners also reported getting sick between September 27 and October 11 in Oregon, Montana, Utah, Wyoming, Nebraska, Kansas, Iowa, Missouri and Wisconsin.

Colorado has the most cases, 26, followed by Nebraska with nine.

“This outbreak may not be limited to states with known illnesses, and the actual number of sick people is likely much higher than the reported number,” CDC officials said on the agency’s outbreak page. “This is because many people recover without medical care and are not tested for E. coli.”

The state health department said the U.S. Food and Drug Administration believes “fresh-cut onions” used on Quarter Pounders — and not on other McDonald’s menu items — may be the culprit, although the U.S. Department of Agriculture is still investigating whether beef patties could be used. the source of the outbreak.

McDonald’s said in a statement on the fast-food chain’s corporate website that “some of the illnesses may be related to chopped onions used in the Quarter Pounder that come from a single supplier serving three distribution centers.”

In a statement, Cesar Piña, McDonald’s Chief Supply Chain Officer for North America, said the company has removed onions from its supplier to the affected areas and temporarily removed the Quarter Pounder from the menu in Colorado and the other states where customers ended up. sick, in addition to parts of New Mexico, Nevada, Oklahoma and Idaho.

The company is working with the CDC to safely reintroduce all items, he said.

“We are working closely with our suppliers to replenish stock for the Quarter Pounder over the coming weeks (timing will vary by local market),” he said in a statement. “In the meantime, all other menu items, including other beef items (including the cheeseburger, hamburger, Big Mac, McDouble and the double cheeseburger) remain unaffected and available.”