A rare inflammatory syndrome affecting some children with the coronavirus has appeared in a small number of cases at a St. Louis hospital.

O'FALLON, Mo. (AP) — A rare inflammatory syndrome affecting some children with the coronavirus has appeared in a small number of cases at a St. Louis hospital.

St. Louis Children’s Hospital has treated “a few” children with COVID-19 — the illness caused by the coronavirus — and for symptoms similar to Kawasaki disease, hospital spokeswoman Laura High said Wednesday. She did not have information about the specific number of cases, or details such as the age of the afflicted children or their conditions.

COVID-19 is far less common in children than adults. Of Missouri’s 10,006 confirmed cases, children under age 20 account for 322, or 3.2%. None of Missouri’s 524 coronavirus deaths have involved children, and generally, doctors continue to believe that most infected children develop only mild symptoms.

But in New York state, two young children and a teenager have died and the state is investigating about 100 cases of the mysterious syndrome, which affects blood vessels and organs and has symptoms similar to Kawasaki disease and toxic shock syndrome. Gov. Andrew Cuomo advised all hospitals to prioritize COVID-19 testing for children presenting with symptoms. New York City Mayor Bill de Blasio urged parents to call their pediatricians if their children have a persistent fever, rash, abdominal pain or vomiting.

Similar cases are showing up elsewhere in the U.S. and in Europe. It wasn’t immediately clear if cases have been reported elsewhere in Missouri. Messages left with the state health department, Cardinal Glennon Children’s Hospital in St. Louis and Children’s Mercy Kansas City were not immediately returned.

At least 3,000 U.S. children are diagnosed with Kawasaki disease each year. It is most common in children younger than 6 and in boys.

For most people, the coronavirus causes mild or moderate symptoms that clear up after two to three weeks. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

Missouri will receive an additional $135 million in federal funds to expand coronavirus testing capabilities, Sen. Roy Blunt said. The funding comes from the Department of Health and Human Services.

Blunt said the funding will increase access to testing and reduce the time it takes to analyze results. It will also improve contact tracing, he said.

“Expanding coronavirus testing capacity is critical to making sure people have the information they need to stop the spread of this disease,” Blunt, a Republican, said in a statement. “As we increase testing, we can more confidently move forward with fully reopening schools and businesses.”