SALT LAKE CITY (ABC4) – Some children who’ve had COVID-19 are suffering serious and even deadly reactions weeks later.

And doctors don’t know why.

“The majority of kids who get MIS-C have been previously healthy,” said Dr. Ngan Truong with U of U Health/Primary Children’s Hospital.

She’s helping lead a national study on long-term effects of Multisystem Inflammatory Syndrome in Children. Parents, she says — are experiencing natural emotions, like fear, over the unknown.

“They have this previously healthy child who now is in the intensive care unit, or in the hospital for the first time ever. And so, I think it’s a very jarring experience,” said Truong.

Truong says MIS-C typically appears two to six weeks after a positive COVID-19 case, or even exposure to the virus. It’s most commonly found in school-aged children. Utah’s first case appeared in April, and she says the syndrome has been more prevalent since November.

She says 70 cases have so far been reported in Utah, with roughly 2,000 nationwide.

“If you know your child has COVID-19, and about a month later starts developing recurrence of fever, or development of fevers, red eyes, rash, belly symptoms, looking more ill, that would definitely be a cause for concern,” said Truong.

“About 50 percent of kids have had what’s called decreased squeeze of the heart, decreased function of the heart, and so we think these kids have had swelling of the heart muscle,” she added.

Andrew Maurer’s 7-year-old daughter Grace has mostly recovered from MISC-C. Six weeks ago, ABC4 spoke to him about the terrifying and confusing sickness that put Grace in the ICU.

She’s back to her normal self, but has undergone a number of tests and still needs an MRI on her heart since doctors say it experienced swelling. It’s unclear if she has or will develop scar tissue, Maurer told ABC4.

“You hear scarring on your daughter’s heart, you think — okay, what does that even mean? What does that mean long term? What does that mean in a year? I don’t know, and frankly, that’s the scary thing,” said Maurer.

He finds solace, though, knowing that Grace will be a part of this study. Hopefully, he says, her case will help doctors understand more about MIS-C as they track the long-term effects of the syndrome.