Even as scientists around the world race to develop treatments for Covid-19, New York has become the centre of a parallel effort to investigate an unnerving aspect of the outbreak: an illness that is sickening a small but growing number of children. The ailment has now been reported in at least 161 children in New York. Hundreds of other children across the US and Europe have also been sickened with the illness, now called multisystem inflammatory syndrome. The syndrome can be characterised by severe inflammation of the heart, blood vessels, the gastrointestinal tract or other organs, believed to be caused