The “vast majority” of children with Covid-19 have mild cases and recover completely, but a small number in a few countries have developed a rare inflammatory syndrome, the World Health Organization (WHO) said on Wednesday.

Italian and British medical experts are investigating a possible link between the coronavirus pandemic and clusters of severe inflammatory disease in infants who are arriving in hospital with high fever and swollen arteries.

Three US children infected with the virus are being treated for a rare inflammatory syndrome that appears similar to one that has raised concerns in Britain, Italy and Spain, a specialist treating them told Reuters on Tuesday.

“I want to emphasise, for all the parents out there, the vast, vast majority of children who get Covid will have mild symptoms and recover completely,” Dr Mike Ryan, the WHO's top emergencies expert, told a virtual news conference on Wednesday.