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DENVER (KDVR) — Three children at Children’s Hospital Colorado are now being investigated for a rare – but potentially deadly – new illness that’s associated with COVID-19.

Doctors first noticed Multisystem Inflammatory Syndrome in Children (MIS-C) in Europe and now there are at least 150 cases in the United States. The illness appears to have killed at least four children.

“Because this is a new and emerging syndrome, there is still a lot we don’t know about MIS-C,” Gov. Jared Polis said Wednesday.

Many of the children, who are usually 5 to 15 years old, with MIS-C have COVID-19 antibodies, which show they have probably been exposed to or had the coronavirus. The new syndrome’s symptoms have been known to show up about a month after children had the coronavirus.

“I know that there are a lot of parents who are afraid and anxious when it comes to thinking about this new SARS coronavirus,” said Dr. Sam Dominguez, an infectious disease expert at Children’s Hospital Colorado. He also said the syndrome should not cause parents to panic, but they should watch for it.

MIS-C Symptoms

  • High fever that often lasts for several days
  • Severe stomach pain
  • Vomiting
  • Diarrhea
  • Low blood pressure

Some children with MIS-C also show symptoms of Kawasaki Disease. They include rash, red tongue, dry and cracked lips, and artery inflammation.

Almost none of the children with the syndrome had breathing issues, a common symptom of the coronavirus.

“This suggests that what we’re seeing in these children is a post-infectious or inflammatory response to the virus, as opposed to direct ongoing damage from the virus itself,” Dominguez said.

Polis said the state did not have enough information about MIS-C to know if it could affect in-person learning in the fall.

In a separate update Wednesday, the Colorado School of Public Health said it estimates that as many as 167,000 Coloradans are suspected of already having had COVID-19. That’s more than seven times higher the number of current documented cases (22,797).

Jill Hunsaker Ryan, the executive director of the Colorado Department of Public Health and Environment, said, “If you think about that, we are really still just at the beginning of this epidemic.”

State health officials saying a slow, gradual reopening of businesses is key to continuing the flattening of the curve.