Preliminary traceback and distribution information reviewed by FDA shows that slivered onions served on Quarter Pounders are a likely source of contamination. FDA is working quickly to confirm that these onions are a source of this outbreak and to determine if these onions were served or sold at other businesses. McDonald’s has temporarily stopped using this type of onion in these states. Diced onions used at McDonald’s are not implicated in this outbreak.
FSIS is conducting traceback on hamburger patties served at McDonald’s in affected states to determine if ground beef is a source of illness. McDonald’s has also temporarily stopped selling Quarter Pounder beef patties in affected states, while the investigation is ongoing to determine the source of the outbreak.