Sarah Simental's parents say she had no other health problems, and still, the virus took her life at such a young age.
"She called me up crying to say that, you know, 'Mom, I'm going to miss Christmas.' And I had to reassure her that it's just a day on the calendar and when she comes home, we'll do Christmas with you. And unfortunately she didn't," said her mother, Deborah Simental.
COVID-19 killed the high school senior in a matter of days. Her mother said Sarah's headache turned into a sore throat and body aches on December 23. It was enough to take her daughter to Silver Cross Hospital.
Her mother said Simental had no health conditions and didn't take any medications. But as her symptoms worsened, doctors airlifted the sick teenager to University of Chicago Hospital.
Her family said that's when things got worse, fast.
"I have no words for it. I just can't believe how fast that it progressed," said her father, Don Simental.
"It literally just ate her through," her mother added. "And no parent should ever have to watch their child go through that."
Their only moment of peace - wrapped in unimaginable agony - was being by their daughter's bedside as she passed.
"She said, "I'm going to be okay, Mom.' And that was the last thing," Deborah Simental said. "So I know that she knows, eventually, we'll all be okay. We're gonna miss her, but we'll be okay."
Sarah would have graduated from Lincoln Way East High School in a few months. She had dreams of caring for animals - a sign of the compassion that her family members say they will miss most.
"I'm thinking that I'm gonna miss out on some real milestones that every mother wants to have with her daughter," Deborah Simental said.