WASHINGTON | Two u.s. studies published on Monday provide a description that is more documented than before the symptoms of the mysterious disease linked to the coronavirus which has affected at least a thousand children in the world, called the syndrome multisystem inflammatory in children (SET-C).
The two studies, published in the New England Journal of Medicine, are based on nearly 300 children and young people under the age of 21 years who have had the Covid-19 (or strong suspicions), identified in the United States between march and may, following an alert launched in the Uk at the end of April and then by the u.s. Centers for prevention and disease control (CDC) in may.
A thousand cases have been reported in the world including these new studies, according to Michael Levin, from Imperial College, London, in an editorial published by NEJM. On 15 may, the european Centre for prevention and disease control had 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 the infection by the virus SARS-CoV-2: a national study evokes 25 days of median duration, while the other, 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 persons under the age of 21 years. As already observed by physicians on both sides of the Atlantic, black children, hispanic or indian origin are relatively more affected than white children.
The most common symptom is not breathing: more than 80 % of the children were, in fact, gastrointestinal disorders (abdominal pain, nausea or vomiting, diarrhea), and many had skin rashes, especially under five years of age. All had fever, very often for more than four or five days. And in 80% of them, the cardiovascular system was concerned. Of 8% to 9% of children have developed an aneurysm of the coronary arteries.
Most children were previously healthy and had no risk factor or pre-existing disease.
80 % were admitted to an intensive care unit, 20 % received respiratory support, invasive, and 2 % died.
At the time of the first alert, the doctors had noted many similarities with Kawasaki disease, which primarily affects infants and very young children and creates inflammation of blood vessels that can cause problems in the heart. These new data confirm that the MIS-C, and Kawasaki have points in common, but that the new syndrome usually affects older children, and triggers inflammation more intense.
The mystery remains over the cause of the syndrome, suspected related to an abnormal response of the immune system. Thin it could have implications on the development of a vaccine and inflammation also observed in multiple organs in adult patients with Covid-19, suggests Michael Levin.