The Centers for Disease Control and Prevention (CDC) said yesterday that fresh slivered onions served on Quarter Pounder hamburgers at McDonald's are the likely source of a multistate outbreak of Shiga toxin-producing Escherichia coli.
In an investigation update, the CDC also said the outbreak of E coli O157:H7 has risen from 75 to 90 cases, with 27 hospitalizations (up from 22). Residents in 13 states have been sickened in the outbreak.
The CDC said the conclusion is based on epidemiologic and traceback information that ties the outbreak to fresh slivered onions supplied to McDonald's by Taylor Farms. Last week, McDonald's stopped using the onions on Quarter Pounders in the affected states, and Taylor Farms recalled the product, contacting customers directly. Other fast-food chains supplied by Taylor Farms also pulled onions from their menus.
The Food and Drug Administration (FDA) said in its investigation update that it has initiated inspections at a Taylor Farms processing center in Colorado and an onion grower of interest in Washington state.
Colorado tests rule out ground beef
Meanwhile, a Colorado Department of Agriculture analysis of subsamples from all lots of fresh and frozen beef patties collected from various McDonald's locations in Colorado, which has reported 29 of the cases, found them all to be negative for E coli. In addition, trace back of beef patties served on Quarter Pounders by the FDA's Food Safety Inspection Service (FSIS) found no evidence that points to ground beef as the source.
Of the 62 people interviewed by CDC, state, and local public health officials, all 62 reported eating at McDonald's, 48 of 58 reported eating an item containing fresh slivered onions, and 46 of 58 reported eating a Quarter Pounder.
E coli O157:H7 causes severe stomach cramps, bloody diarrhea, and vomiting. Symptoms typically start 3 to 4 days after ingesting the bacteria, and most people recover without needing treatment. One death has been reported in the outbreak, in a patient in Colorado, and two people have developed hemolytic uremic syndrome, which can cause kidney failure.
Although the true number of sick people in the outbreak is likely higher, and more states may be affected, the CDC says that because of the actions taken by McDonald's and Taylor Farms, the risk to the public is "very low."
