WASHINGTON | Two US studies released on Monday provide a more documented description than before of the symptoms of the mysterious coronavirus disease that has affected at least a thousand children worldwide, called multisystem inflammatory disease syndrome in children (MIS-C).
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The two studies, published in the New England Journal of Medicine (NEJM), are based on nearly 300 children and young people under the age of 21 who have had COVID-19 (or who are suspected of having had the disease), identified in the United States between March and May, following an alert launched in the United Kingdom at the end of April, then by the American Centers for Disease Prevention and Control (CDC) in May.
A thousand cases have been reported worldwide including these new studies, according to Michael Levin of Imperial College London in an editorial published by NEJM. On May 15, the European Center for Disease Prevention and Control reported 230 cases in Europe, including two deaths in France and the United Kingdom.
As we suspected, it is clear that the syndrome appears in a second time, several weeks after infection with the SARS-CoV-2 virus: a national study suggests 25 days of median duration, while another, in New York, indicates that the majority of cases occurred one month after the peak of the pandemic in the city.
The disease is confirmed as very rare: 2 cases per 100,000 people under the age of 21. As already observed by doctors on both sides of the Atlantic, black, Hispanic or Indian children are relatively more affected than white children.
The most common symptom is not respiratory: more than 80% of children actually had gastrointestinal complaints (abdominal pain, nausea or vomiting, diarrhea) and many had rashes, especially those under the age of five. All had fever, very often for more than four or five days. And in 80% of them, the cardiovascular system was affected. From 8 to 9% of children have developed an aneurysm of the coronary arteries.
Most children were previously healthy and had no risk factors or preexisting disease.
80% were admitted to intensive care, 20% received invasive respiratory assistance and 2% died.
At the time of the first alerts, doctors had noted many similarities with Kawasaki disease, which mainly affects infants and very young children and creates inflammation of the blood vessels that can cause heart problems. These new data confirm that MIS-C and Kawasaki have some things in common, but that the new syndrome generally affects older children and triggers more intense inflammations.
The mystery remains about the cause of the syndrome, which is believed to be linked to an abnormal immune system response. Clarifying it could have implications for vaccine development and the inflammations also seen in multiple organs in adults with COVID-19, suggests Michael Levin.