LOS ANGELES -- Fresh, slivered onions served on Quarter Pounders and other menu items from McDonald's are the likely source of E. coli outbreak in the United States, said the US Centers for Disease Control and Prevention (CDC) on Wednesday.

A total of 90 sicken cases caused by E. coli have been reported across 13 U.S. states as of Wednesday, including 15 new cases, according to latest CDC data.

Among these cases, 27 were hospitalized and one dead.

The CDC said more illnesses have been reported, but they are from before McDonald's and Taylor Farms took action to remove onions from food service locations.

Due to the product actions taken by both companies, the CDC said it believes the risk to the public is very low.

E. coli are bacteria found in many places, including in the environment, foods, water, and the intestines of people and animals.

Most E. coli are harmless and are part of a healthy intestinal tract. But some E. coli can make people sick with diarrhea, urinary tract infections, pneumonia, sepsis, and other illnesses, according to the CDC.