A sign is seen outside a McDonald’s restaurant in Pittsburgh on June 25, 2019. E. coli food poisoning linked to McDonald’s Quarter Pounder hamburgers has sickened at least 49 people in 10 states, including one person who died and 10 who were hospitalized.

Gene J. Puskar/AP

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Gene J. Puskar/AP

E. coli food poisoning linked to McDonald’s Quarter Pounder hamburgers has sickened at least 49 people in 10 states, including one person who died and 10 who were hospitalized, federal health officials said Tuesday.

The death of an elderly person was reported in Colorado and a child was hospitalized with serious kidney complications, the U.S. Centers for Disease Control and Prevention reported.

Between September 27 and October 11, infections were reported in Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin and Wyoming. Colorado has the most cases with 27, followed by Nebraska with nine.

All people interviewed in connection with the outbreak reported eating at McDonald’s before becoming ill, and most mentioned eating Quarter Pounder hamburgers, the CDC said. The U.S. Department of Agriculture, the Food and Drug Administration and state health officials are also investigating.

A specific ingredient has not been identified as the cause, but investigators are focusing on onions and beef. A preliminary FDA investigation suggests that slivers of onion served on the burgers are a likely source of contamination. The USDA is investigating the hamburger patties.

McDonald’s says some of the illnesses may be related to onions

In a statement, McDonald’s officials said initial results indicate some illnesses are linked to onions purchased from a single supplier. The company has stopped selling the onion slices and temporarily removed the Quarter Pounder from menus in the affected states as well as parts of Idaho, Nevada, New Mexico and Oklahoma.

“We take food safety very seriously and it is the right thing to do,” the statement said.

E. coli bacteria are found in the intestines of animals and are found in the environment. Infections can cause serious illnesses such as fever, stomach cramps and bloody diarrhea. People who develop symptoms of E. coli poisoning should seek medical attention immediately and tell the provider what they have eaten.

The news comes in an already difficult year for the Chicago-based McDonald’s chain. In the second quarter, global same-store sales fell for the first time in nearly four years as inflation-weary customers avoided eating out or opted for cheaper options. The company responded with a $5 meal deal that launched in U.S. restaurants in late June and was recently extended through December. The Quarter Pounder is not included in the offer.

McDonald’s shares fell 9% in after-hours trading on Tuesday following the CDC’s announcement.

The type of bacteria involved in this outbreak, E. coli O157:H7, causes about 74,000 infections each year in the United States, resulting in more than 2,000 hospitalizations and 61 deaths. Infections are particularly dangerous for children under 5 years of age and can lead to acute kidney failure.