Four days after the Centers for Disease Control and Prevention issued its alert about an outbreak it claimed was linked to the sandwich, it reported 75 cases of E. coli, 22 of which required hospitalizations, and one death. While the CDC reported these cases across 13 states, McDonald’s shuttered production across 12 states, including Colorado, Kansas, Wyoming, Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma, and Utah, according to its North American Chief Supply Chain Officer Cesar Piña.

“Over the weekend, McDonald’s was informed that the Colorado Department of Agriculture has completed their testing, the results of which confirm that there was no detection of  E. coli in the samples taken of Quarter Pounder beef patties from restaurants in this area. We’ve been informed there is no further testing planned for beef patties,” Piña wrote. “Overlaying the CDC’s Epidemiological data with our Supply Chain traceback data, we have ruled out Quarter Pounder patties as the source.”

Attention turned to McDonald’s onion supplier, Taylor Farms, as the outbreak’s origin. While the CDC credited Taylor Farms for voluntarily recalling its onions, it remains to be seen where the onions came from, as Colorado’s Agriculture Department said it had “no information suggesting onions grown in Colorado are linked to this outbreak.”

As a result, the restaurants in the affected states will produce Quarter Pounders without slivered onions. McDonald’s removed further contaminated products from all its restaurants.

“Due to the product actions taken by both companies, CDC believes the risk to the public is very low,” its website read.

E. coli, otherwise known as Escherichia coli, induces symptoms of high fevers, dehydration, vomiting, severe stomach cramps, bloody diarrhea, dizziness, and dry mouth and throat. These typically begin three to four days following ingestion.

Those most at risk are children, the elderly, and those with compromised immune systems. One of the reported hospitalizations was a child who developed a kidney disease called hemolytic uremic syndrome.