Slivered onions likely source of E. coli outbreak at U.S. McDonald's, CDC says

Slivered onions served onMcDonald's items including Quarter Pounder hamburgers were the likely source of an E. coli outbreak that has sickened at least 90 people in the U.S., the Centers for Disease Controland Prevention said on Wednesday.

The outbreakwas firstreported on Oct. 22.

The U.S. Food and Drug Administration and the companyhave confirmed that Taylor Farms was the supplier for theaffected locations, and it has since recalled several batches ofyellow onions produced in a Colorado facility.

The CDC said the number of infected people has risen, from 75 to 90. Twenty-seven people have been hospitalized due tothe illness, which has already killed one person.

As of Oct. 24, two people had developed hemolytic uremic syndrome, a serious condition that can cause kidney failure.

The E. coli O157:H7 strain that led to the McDonald's outbreak is said to cause "very serious disease," especially for theelderly, children and people who are immunocompromised.

The FDA noted thatsymptoms begin anywhere from a few days after consuming contaminated food to up to nine days later.

On Sunday, the company along with the Colorado Department ofAgriculture also ruled out the possibility of beef patties beinga source of the outbreak.

As of Oct. 30, the outbreak had affected people in Colorado, Kansas,Utah, Wyoming, Iowa, Missouri, Montana, Nebraska, New Mexico,Oregon, Wisconsin, Washington and Michigan.McDonald's Canada said it has not been not impacted in any way.

Colorado has reported the highest infections with 29 peoplewho have fallen sick, while Montana reported 17 infections.

McDonald's said that it would resume selling QuarterPounderburgers this week after it temporarily took the itemoff the menu in a fifth of its 14,000 U.S. restaurants.

Chris Kempczinski, CEO and president of McDonald's, apologized for the outbreak on Tuesday on a conference call with investors.

"Nothing is more important to us than the safety of our customers," Kempczinksi said. "The recent spate of E. coli casesis deeply concerning, and hearing reports of how this has impacted our customers has been wrenching for us."