McDonald’s is bringing its Quarter Pounders back to all restaurants this week amid an ongoing outbreak of E. coli attributable to the ingredients of the fast food chain’s famous hamburger. The outbreak has sickened at least 75 people in 13 states, according to the Centers for Disease Control and Prevention (CDC) reported Friday. One person died.

During a press briefing on Sunday, McDonald’s confirmed that the beef used in its Quarter Pounder patties is not the source of contamination in the ongoing outbreak. Testing by the Colorado Department of Agriculture found the beef samples were negative for E. coli, USA Today reported.

“The issue appears to be limited to a particular ingredient and geographic area, and we remain confident that any contaminated product related to this outbreak has been removed from our supply chain and is outside of all McDonald’s restaurants,” Cesar Piña , head of McDonald’s supply chain. Officer, North America, said in the release.

McDonald’s Quarter Pounders will be served without chopped onions, supplied by California producer Taylor Farms. Last Thursday, Taylor Farms issued a recall of whole and diced onions due to possible E. coli contamination, foodservice distributor American foods advertised. A Food and Drug Administration (FDA) investigation is currently underway at the Taylor Farms facility in Colorado Springs.

Nine hundred McDonald’s restaurants in 12 states received onions from Taylor Farms. McDonald’s has stopped using onions from Taylor Farms’ Colorado facilities indefinitely, the company said. NPR.

Onion-less Quarter Pounders will return to Colorado, Kansas, Utah and Wyoming, where the burgers have been removed from all McDonald’s restaurants. The menu item will also return to restaurants in parts of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma.

McDonald’s has “asked its beef suppliers to produce a new supply of quarter-pound beef for restaurants,” USA Today reported.

As of October 25, 22 people had been hospitalized – including two people who developed serious kidney complications – after eating Quarter Pounder burgers containing sliced ​​onions from Taylor Farms. The CDC previously reported 49 illnesses in 10 states. That number quickly grew to 75 illnesses in 13 states.

The illnesses were reported between September 27 and October 11. Colorado currently has the highest number of cases with 27, followed by Montana with 13 and Nebraska with 11. Other states have reported five or fewer illnesses.

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The CDC said the total number of cases linked to the ongoing outbreak is likely much higher than reported. This is because some consumers may not experience immediate symptoms or need medical attention after becoming ill. The number of states affected by the outbreak is also expected to increase.

Last week, McDonald’s announced it would temporarily remove the Quarter Pounder from restaurants in affected states.

“We are working closely with our suppliers to replenish the supply of the Quarter Pounder in the coming weeks,” Piña said in a statement Tuesday, per NPR. “In the meantime, all other menu items, including other beef items (including the Cheeseburger, Hamburger, Big Mac, McDouble and Double Cheeseburger), are unaffected and are available.”

Three lawsuits have been filed against McDonald’s in connection with the E. coli. THE first trial was filed just one day after the CDC issued a food safety alert regarding the Quarter Pounder.

More lawsuits are expected to be filed soon.