US health officials are investigating a multistate Escherichia coli outbreak linked to McDonald's Quarter Pounder hamburgers.
In a food safety alert posted yesterday, the Centers for Disease Control and Prevention (CDC) said the outbreak strain of E coli O157:H7 has infected 49 people in 10 states, with 10 hospitalizations and 1 death. More than half of the cases (26) have been reported in Colorado. The other affected states are Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin, and Wyoming.
Along with the CDC, the US Department of Agriculture's Food Safety and Inspection Services (USDA-FSIS), the Food and Drug Administration (FDA), and public health and regulatory agencies in several states are collecting information on the outbreak.
Slivered onions may be the source
Of 18 people interviewed so far, all report eating at McDonald's prior to their illness, 16 report eating a beef hamburger, and 12 say they ate a Quarter Pounder. But a specific ingredient has not yet been confirmed as the source of the outbreak.
USDA-FSIS is conducting trace-back investigations on hamburger patties served at McDonald's to determine if the ground beef is the source of the illness. The CDC, however, said preliminary trace-back and distribution data reviewed by the FDA indicate that fresh slivered onions could be the source. The Colorado Department of Public Health & Environment notes that the slivered onions used on Quarter Pounders are not on other McDonald's menu items.
In a statement today, McDonald's said the onions are sourced from a single supplier that serves three distribution centers, and that the company has paused the distribution of all slivered onions in the impacted areas and instructed local restaurants to remove the product from their supply.
McDonald's said it's also temporarily taking Quarter Pounders off the menu in restaurants in Colorado, Kansas, Utah, and Wyoming, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, and Oklahoma.
"We take food safety extremely seriously, and it's the right thing to do," the company said in the statement.
No products have been recalled yet.
Many more cases likely
E coli O157:H7 is a Shiga toxin–producing strain of E coli that 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. In addition to the one death, one hospitalized patient developed hemolytic uremic syndrome, which can cause kidney failure and even death.
The CDC said illnesses in the outbreak started on dates ranging from September 27 to October 1. The age range of case-patients is 13 to 88 years. The agency advises people to call their healthcare provider if they've recently eaten a Quarter Pounder and are experiencing E coli symptoms.
Michael Osterholm, PhD, MPH, director of the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP), which publishes CIDRAP News, says the number of people affected by the outbreak is likely much higher.
"If they've picked up this many already, there has to be a lot more," Osterholm said. "Based on our previous experience with foodborne outbreaks, seeing this many cases this early in an outbreak surely does support that there are many not-yet-reported cases."