Rare Coronavirus-linked Syndrome Has Affected Hundreds of U.S. Children

Almost 300 children in the U.S. are known to have suffered from a rare inflammatory syndrome thought to be linked to the coronavirus which causes COVID-19, according to research.

Those diagnosed with the condition known as multisystem inflammatory syndrome in children (MIS-C) are sick enough to require hospital treatment; have a fever lasting for at least 24 hours; signs of inflammation in their body; and problems with multiple organs, according to the U.S. Centers for Disease Control and Prevention. Patients must also be 21-years-old or under, and either have tested positive for the COVID-19-causing coronavirus, had a positive antibody test, or been exposed to a COVID-19 patient four weeks before their MIS-C symptoms start.

Two papers published in the New England Journal of Medicine on Monday show at least 285 children have had MIS-C in the U.S. since March.

In one study, researchers found 186 cases of MIS-C had been reported in 26 states between March 15 and May 20. The study excluded cases in New York State that were featured in the other study.

On average, the children were aged 8-years-old and hospitalized for seven days. A total of 62 percent were male, 73 percent were previously healthy, and 70 percent had either tested positive for the coronavirus after a swab or antibody test. Some 80 percent needed intensive care treatment, and a fifth were hooked up to a ventilator. The illness of 40 percent of patients had similarities to a rare condition called Kawasaki's disease, characterized by inflammation in the coronary arteries and other blood vessels.

The team concluded that MIS-C in children linked with the coronavirus "led to serious and life-threatening illness in previously healthy children and adolescents."

The study on children in New York featured 95 patients confirmed to have MIS-C in the state between March 1 and 10. In this group, 54 percent were male, and most children were aged between six and 12-years-old. Some 80 percent needed intensive care treatment, and two died. Most stayed in hospital for six days.

In an editorial accompanying the articles, Professor Michael Levin, Chair in Paediatrics and International Child Health at the U.K.'s Imperial College London who wasn't involved in the studies, said approximately 1,000 cases of MIS-C have been reported worldwide amid the COVID-19 pandemic.

However, Levin said reports published on the condition "have used a variety of hastily developed case definitions based on the most severe cases, possibly missing less serious cases."

But he said a "consistent" picture is emerging, that MIS-C is uncommon, affecting 2 in 100,000 people aged 21 and younger, and usually happens two to four weeks after a child is infected by the coronavirus.

Professor Lawrence C. Kleinman in the Department of Pediatrics at the Rutgers Robert Wood Johnson Medical School and Bristol-Myers-Squibb Children's Hospital who co-authored the 26-state paper, said in a statement: "The study highlights our ever-changing understanding of COVID-19 in children.

"We have moved from thinking that COVID-19 spares children to understanding that children can get very sick. Children play an important role in the pandemic."

Fellow co-author Steven Horwitz, Assistant Professor of pediatric critical care at the Rutgers Robert Wood Johnson Medical School, said in a statement that those with MIS-C can get "very sick" and may need treatments to support their breathing and heart function.

"Still, with proper identification and treatment, thankfully the majority of these children and adolescents get better and many do so very quickly."