The World Health Organization has said it is studying a possible link between Covid-19 and a rare inflammatory illness that has sickened children in Europe and the United States, some of whom later died.
In recent weeks, several countries have reported cases of children affected by the condition with symptoms similar to those of a rare condition, Kawasaki disease.
"Initial reports hypothesise that this syndrome may be related to Covid-19," WHO head Tedros Adhanom Ghebreyesus told a virtual briefing.
"It is critical to urgently and carefully characterise this clinical syndrome, to understand causality and to describe treatment interventions," he said.
He said the WHO had developed a preliminary case definition for the disease, which it has dubbed "Multisystem Inflammatory Syndrome in Children", and was calling on clinicians worldwide to "be on the alert and better understand this syndrome."
His comments came after a doctor in France said that a nine-year-old boy there who had tested positive for Covid-19 had died from the syndrome, marking the first such death in the country.
Similar child fatalities are being investigated in New York and London.
Earlier this week, a London children's hospital said that a 14-year-old boy with no underlying health conditions had died from the disease and had tested positive for the coronavirus.
In New York, Governor Andrew Cuomo said that three children in the state had died and more than 100 cases were being investigated.
There have been 125 reported cases in France between 1 March and 12 May, according to the country's public health agency. The patients ranged in age from one to 14.
Here, the Chief Medical Officer, Dr Tony Holohan has said that advice around Kawasaki disease, a rare condition that affects children under five, is mainly aimed at clinicians.
Kawasaki is an inflammatory illness associated with Covid-19.
Dr Holohan has asked doctors be suspicious that this could be an unusual set of circumstances and could be a possible explanation for a sick child and to report it.
''Temperatures in children are very common and it is unlikely to be this'' [Kawasaki], according to the the Chief Medical Officer.
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WHO expert Maria Van Kerkhove told today's briefing that the link to Covid-19 had yet to be clearly established, since some of the children with the syndrome had not tested positive for the virus.
"We need to understand if this syndrome is related to Covid-19 or not," she said.
"We need all countries to be on alert for this."
WHO emergencies director Michael Ryan, meanwhile, said that even if the syndrome is related to Covid-19, it may not be caused by the coronavirus itself.
"What we don't know yet is whether those rare things that happen are associated directly to the virus ... or are we seeing also the result of the immune response to the virus," he said.
He also stressed that the syndrome impacting children appeared to be "very rare", and had only become apparent because of swelling numbers of Covid-19 cases.
"It doesn't mean that the disease is changing in kids," he said.
"What it means is that when you get a very large number of children with the disease, you will see a very rare occurrence happen."
