By Hollie Silverman and Dakin Andone, CNN

(CNN) -- Two children in South Carolina have been diagnosed with the coronavirus-related pediatric inflammatory syndrome, according to the state's Department of Health and Environmental Control.

The children are both under the age of 10, DHEC said in a news release Sunday. One is located in the Midlands region in central South Carolina. The other is in the Pee Dee region in the northeastern part of the state.

Multisystem inflammatory syndrome in children, or MIS-C, is a potential complication seen in some children and teenagers following Covid-19 infections or exposure to those with Covid-19.

The US Centers for Disease Control and Prevention issued a health advisory to doctors across the country in May, warning them to be on the lookout for the syndrome. Symptoms include fever, stomach pain, vomiting, a rash and fatigue, according to the CDC.

"We continue to see more and more young people, especially those under 20, contracting and spreading COVID-19, and we know MIS-C is a threat to our youngest South Carolinians," State Epidemiologist Dr. Linda Bell said in a news release. "MIS-C is a serious health complication linked to COVID-19 and is all the more reason why we must stop the spread of this virus."

"Anyone and everyone is susceptible to COVID-19 as well as additional health risks associated with it, which is why all of us must stop the virus by wearing a mask and stay six feet away from others," Ball said. "These simple actions are how we protect ourselves and others, including our children."

Experts are still learning about MIS-C and trying to determine why some children experience it while others do not.

But two recent studies -- both published last month in the New England Journal of Medicine -- show MIS-C can cause serious symptoms and is potentially fatal. They showed that 80% of patients with MIS-C required treatment in intensive care.

In one report, CDC researchers analyzed 186 cases from 26 states between March 15 and May 20.

Patients were hospitalized for a median of seven days and 20% required ventilation to help them breathe. Four patients, or 2%, died. The median age of patients was 8 years old. Just 7% of patients were under a year old, most of the rest were between a year old and 14, and 16% were ages 15 to 20.

The second report, by the New York State Department of Health, examined 99 children with suspected or confirmed MIS-C who were hospitalized between March 1 and May 20. In that study, the median hospital stay was six days.