Seventy-five people across 13 states have fallen ill in an E. coli outbreak attributed to McDonald's Quarter Pounders.

Health officials say that recalls of onions — the suspected source of the contamination — would help lessen the risk to consumers. Other major fast-food chains have also stopped offering onions.

Early information showed that uncooked slivered onions used on the burgers “are a likely source of contamination,” the FDA said.