Global health experts are looking into reports of a rare but serious syndrome affecting children.

The World Health Organisation (WHO) said it had asked its global networks of clinicians to be on “alert” for the rare phenomenon, which was first noticed by medics in the UK.

Fewer than 20 children in England have been admitted to hospital with the syndrome, which causes a toxic shock-style inflammatory reaction.

The illness may be caused by the novel coronavirus but experts are not sure because some of the affected children have not tested positive for Covid-19.

There are some recent rare descriptions of children in some European countries that have had this inflammatory syndrome, which is similar to the Kawasaki syndrome

It follows an alert shared with NHS trusts and GP groups by NHS England asking medics to remain on high alert for signs of the disease.

The condition is said to be similar to Kawasaki disease, which mainly affects children under the age of five, with symptoms including a high temperature for five days or more, rashes and swollen glands in the neck.

Dr Maria Van Kerkhove, WHO technical lead for Covid-19, said: “We are aware of this report, which came out of the United Kingdom, about a small number of cases amongst children with this inflammatory response.

“We’re looking at this with our clinical network.

“There are some recent rare descriptions of children in some European countries that have had this inflammatory syndrome, which is similar to the Kawasaki syndrome.

“What we’ve asked for is for the global network of clinicians to be on alert for this, and to ensure that they capture information on children systematically so that we could better understand what is occurring in children, and so that we could better improve our understanding and guide treatment.

“But it seems to be very rare and only in maybe one or two countries so far and additional countries that have not recorded this yet, but this is something that the clinical network is looking into specifically.”

WHO officials stressed that the vast majority of children who get Covid-19 will have a mild infection and “recover completely”.

It's really important that paediatricians and clinicians get time to collect information and share that

Dr Mike Ryan, executive director of the WHO health emergencies programme, told a press briefing in Geneva: “The Sars-Cov-2 virus causing Covid-19 obviously is causing inflammation and attacks tissue, other than lung tissue.

“We are in a situation where clinicians are looking at what those other effects of having this coronavirus infection are.

“And we’ve seen this in the past with many emerging diseases, they don’t necessarily only attack one type of tissue, there can be multiple organs affected and many of you have seen the reports of other organs that have been affected with this disease.

“So it’s really important that this information is shared around the world.

“It’s really important that paediatricians and clinicians get time to collect information and share that.

“But again, just to reassure parents out there – this is a rare complication.

“And one should always be watchful of the children who are experiencing infectious disease or any deterioration of the condition, but I think it’s important that parents out there are reassured.”

Meanwhile, the global health body said in its tri-weekly briefing that Covid-19 can “wreak havoc” and “cause upheavals”.

Going forward, people may need to “adjust the way we lead our lives” while the virus is present, WHO experts added.

The WHO’s director general Dr Tedros Adhanom Ghebreyesus said: “This virus can wreak havoc. It’s more than any terrorist attack. It can bring political, economic and social upheavals.

“More than ever, the human race should stand together to defeat this virus.”

Dr Ryan continued: “If we wish to get back to a society where we don’t have lockdowns, then society may need to adapt – for a medium or potentially a longer period of time – in which our physical and social relationships with each other will have to be modulated by the presence of the virus.

“We will have to be aware if the virus is present, and we will have to as individuals and families and communities do everything possible on a day-to-day basis to reduce the transmission of that virus. And that may mean adjusting the way we live our lives.”