McDonald’s deadly Quarter Pounder E. coli outbreak is likely bigger than we know

One person is dead and 48 others across 10 states have been sickened in an E. coli O157:H7 outbreak that appears to be linked to McDonald's Quarter Pounders and the slivered onions used on the burgers, according to the Centers for Disease Control and Prevention.

McDonald's has paused distribution of the slivered onions and removed Quarter Pounders from the menus of restaurants in areas known to be affected. As of now, those areas include Colorado, Kansas, Utah, and Wyoming, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma.

However, the CDC was quick to note that the size and span of the outbreak are likely larger than is currently known. "This outbreak may not be limited to the states with known illnesses, and the true number of sick people is likely much higher than the number reported," the agency said in its outbreak notice posted Tuesday afternoon.

The agency notes that many people sickened by E. coli-tainted food will recover without medical care and will not be tested for the bacterial pathogen, meaning those illnesses will never be linked to the outbreak. Additionally, for cases that do require medical care, there are delays in linking illnesses to outbreaks. The CDC notes that it usually takes 3 or 4 weeks to connect an illness to an outbreak, making it likely that recent illnesses may not be counted yet.

Still, the CDC also notes that this appears to be a "fast-moving outbreak." Of the 49 cases in 10 states linked so far, three were identified as recently as October 11. Overall, the illness onsets span from September 27 to October 11.

The swift identification is likely aided by the fact that sickened people have unusually clear memories of what they ate. "Everyone interviewed has reported eating at McDonald’s before their illness started, and most specifically mentioned eating a Quarter Pounder hamburger," the CDC reported. Food recall surveys done amid outbreaks don't always reveal such a clear picture.

The specific source of the E. coli outbreak strain—an E. coli O157:H7, a Shiga toxin-producing E. coli (STEC)—has not been determined, the CDC said. But investigators have narrowed their focus to the fresh quarter-pound beef patties and slivered onions used on the popular Quarter Pounder. The CDC notes that the quarter-pound beef patties are only used on Quarter Pounders, and the slivered onions are "primarily" used on Quarter Pounders.

Deadly contamination

As in most outbreaks, many of the 49 cases identified so far are on the severe end of the illness spectrum. Of the 49 cases, 10 have required hospitalization. An older person in Colorado died from the illness. And the hospitalizations include a child who has developed hemolytic uremic syndrome (HUS), a dangerous complication of a STEC infection that can lead to kidney failure, chronic kidney disease, other permanent health conditions, and even death.

A main source of STEC is cattle. The pathogen colonizes the animals' intestines and can spread in feces. Humans get exposed via the fecal-oral route. Contaminated, undercooked meat can spread the germ. But produce can also be an infection source if it is contaminated during growing or processing via fecal matter or contaminated water, such as runoff from nearby farms.

The people most vulnerable to STEC are children ages 5 and under, adults 65 and over, and people with compromised immune systems. The CDC advises anyone who recently ate a Quarter Pounder to call their health care provider if they begin having severe symptoms of an E. coli infection. Initial symptoms tend to begin three to four days after eating contaminated food and include stomach cramps, diarrhea (often bloody), and vomiting.

Symptoms of severe infection include:

• Diarrhea and a fever higher than 102°F
• Diarrhea for more than three days that is not improving
• Bloody diarrhea
• So much vomiting that you cannot keep liquids down
• Signs of dehydration, such as not peeing much, dry mouth and throat, and feeling dizzy when standing up

In a statement, McDonald's said that a "subset" of the illnesses reported so far appear linked specifically to the slivered onions on Quarter Pounders, which are "sourced by a single supplier that serves three distribution centers." But the company added that "out of an abundance of caution, we are also temporarily removing the Quarter Pounder from restaurants in the impacted area ... We take food safety extremely seriously and it’s the right thing to do."

The company said it hopes to restore Quarter Pounders in impacted areas in "the coming weeks" but that "all other menu items" are "unaffected and available."

One of the most notorious E. coli O157: H7 outbreaks of all time was also linked to burgers from a fast food chain: the tragic 1992–1993 Jack in the Box outbreak, which was caused by contaminated beef. In that outbreak, over 700 people were sickened; most were children under the age of 10. Four children died in the outbreak, all age 6 and under. Of the survivors, 178 were left with permanent injuries, including kidney and brain damage.