A 15-year-old high school freshman is hospitalized with severe complications from food poisoning after eating McDonald’s Quarter Pounder hamburgers three times in the previous weeks a deadly E. coli outbreak was determined.

Kamberlyn Bowler of Grand Junction, Colorado, had to be flown 250 miles to a hospital near Denver in mid-October, where she underwent 10 days of dialysis in an urgent effort to save her kidneys.

She is one of at least 75 people sickened and 22 hospitalized in the outbreak, which is tentatively traced to contaminated onions. In Mesa County, where Kamberlyn lives, 11 people are sick and one person has died. Here’s what federal health officials said diced onions used on the burgers are a likely cause of the outbreak.

Kamberlyn’s mother, Brittany Randall, worried about her daughter’s health after the ordeal and was shaken by the idea that a burger could possibly cause so much harm.

“It’s pretty scary to know that we trust so much that we’re eating something healthy and it’s broken,” Randall said.

She wants to sue the fast food chain after Kamberlyn was infected the E. coli O157:H7 bacteria confirmed in the outbreak.

This bacteria produces a dangerous toxin that medical experts say can cause a serious complication of kidney disease known as hemolytic uremic syndrome. Many children remain in the hospital for weeks and some subsequently require a kidney transplant, Dr. Myda Khalid, a kidney specialist at Riley Hospital for Children in Indiana who is not involved in Kamberlyn’s care.

“Time is of the essence,” Khalid said. “We have to come through this window and do it with great care,” she said.

The condition can be fatal, but most children eventually recover, she said.

Kamberlyn said she ate McDonald’s Quarter Pounders with cheese, extra pickles – and onions – three times between Sept. 27 and Oct. 8. She said the burgers were easy to get during a football halftime break and while watching a softball game at school.

Over the next few days, she became sick and suffered from fever, vomiting, diarrhea and painful stomach cramps.

“I couldn’t get up,” she remembers. “I couldn’t eat. I couldn’t drink. I survived on popsicles. I felt like crap.”

Randall, who works as a prison guard, has three older children and thought her young daughter might just have the flu. But when Kamberlyn texted her to say she had blood in her stool and urine and was vomiting blood, Randall said she knew it was serious.

On Oct. 11, Kamberlyn went to a hospital in Grand Junction. Doctors said she probably had a gastrointestinal illness. She was sent home with instructions to stay hydrated. On October 17, she was not improving and returned to the emergency room. At the time, tests showed Kamberlyn was suffering from acute kidney failure, her mother said. She was flown to Colorado Children’s Hospital in Aurora, near Denver, where she remained Tuesday.

Chris Kempczinski, chairman, president and CEO of McDonald’s, apologized for the outburst in a conference call with investors on Tuesday.

“Nothing is more important to us than the safety of our customers,” said Kempczinksi. “The recent wave of E. coli cases is deeply concerning, and we are distressed by reports of how this has impacted our customers.”

Randall said her daughter’s future health status – and medical costs – are uncertain.

“Hospital bills are going up,” she said. “And I’m a single mom and I just don’t know if I’ll necessarily be able to afford everything that comes my way after all of this. And I don’t know what the future looks like either.”

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The Associated Press Health and Science Department receives support from the Science and Educational Media Group of the Howard Hughes Medical Institute. The AP is solely responsible for all content.