One person has died and 75 others have fallen ill due to an E. coli outbreak linked to McDonald’s Quarter Pounders.

CDC. E. coli Outbreak Linked to McDonald’s Quarter Pounders. October 25, 2024.

 

Thirteen states are impacted by the outbreak, which investigators believe is likely due to raw onions used in Quarter Pounders.

CDC. Investigation Update: E. coli Outbreak, McDonald’s Quarter Pounders – October 22, 2024. October 25, 2024.

 

“Epidemiologic data show that Quarter Pounder hamburgers served at McDonald’s are contaminated with E. coli and are making people sick. Early information from FDA [the Food and Drug Administration] indicates onions may be a source of this outbreak. Investigators from all agencies are working quickly to determine the contaminated ingredient,” the CDC said in an update.

CDC. Investigation Update: E. coli Outbreak, McDonald’s Quarter Pounders – October 22, 2024. October 25, 2024.

 

While 75 cases have been reported to the Centers for Disease Control and Prevention (CDC) so far, the actual number of people who have fallen ill due to the outbreak is likely much higher. The CDC notes that this is because many people will recover from an infection without medical care or testing for E. coli.

It also typically takes 3 to 4 weeks for investigators to determine whether a sick person is part of an outbreak.

 

How the outbreak began

 

Those infected by the McDonald’s outbreak first began falling ill between September 27, 2024, and October 10, 2024. Most of those who are sick reported eating at McDonald’ss before experiencing symptoms.

CDC. Investigation Update: E. coli Outbreak, McDonald’s Quarter Pounders – October 22, 2024. October 25, 2024.

 

Twenty-two people have been hospitalized and two have developed hemolytic uremic syndrome (HUS), which can cause kidney failure.

An older adult in Colorado has died, but they did not develop HUS

“These infections can involve, obviously, most commonly the intestinal tract, causing upset that can result in vomiting and diarrhea and, as a consequence, dehydration. Particularly for the very young and older persons who might be frail and somewhat disabled, the dehydration, in particular, is usually the source of the more serious infections that require attention in the hospital and can, on occasion, as in this instance, lead to death,” William Schaffner, MD, an infectious disease expert at Vanderbilt University, tells MDLinx.

Due to the outbreak, Quarter Pounders will be temporarily unavailable in some states while changes are made to the supply chain.

CDC. E. coli Outbreak Linked to McDonald’s Quarter Pounders. October 25, 2024.

 

 

Slivered onions recalled

 

Taylor Farms, which supplies slivered onions to McDonald’s restaurants in impacted locations, has initiated a voluntary recall of some of its products as the investigation continues.

CDC. E. coli Outbreak Linked to McDonald’s Quarter Pounders. October 25, 2024.

 

The beef patties used in Quarter Pounders are not used in other McDonald’s products. The slivered onions are also used primarily on Quarter Pounders.)

Dean Blumberg, MD, Chief of Pediatric infectious Diseases at the University of California, Davis, says there are numerous waysthat  the onions could have been contaminated.

“The onions can be contaminated in the field, but they can also be contaminated through processing … During the processing, as they're slivered, then you can contaminate a whole lot of these onions. I think that's how the contamination most likely occurred, whether it's due to contaminated equipment [or] whether it's due to certain individuals who were involved in the processing and maybe some compromising of the hygiene protocols. It's really not known, but there [are] multiple opportunities along the way during processing that contamination may occur,” Dr. Blumberg says.

 

Risk to the public believed to be very low

 

The CDC says that due to the response from McDonald’s and Taylor Farms, the risk to the public from the E. coli outbreak is very low.

CDC. E. coli Outbreak Linked to McDonald’s Quarter Pounders. October 25, 2024.

 

Both Drs. Blumberg and Schaffner say that physicians have an important role to play in remaining vigilant about detecting potential cases.

“Most hospitals and labs will be doing the rapid testing—the PCR testing for this—and will readily identify the causative agent. This is useful to know for several reasons. One is for isolation, but another is for appropriate treatment because antibiotic treatment theoretically can increase the risk of progressing to hemolytic uremic syndrome and then renal failure and other complications. You wouldn't want to give antibiotics unless there's an invasive infection, and then appropriate monitoring of patients in order to see if they are progressing to hemolytic uremic syndrome,” Dr. Schaffner adds.