Up to 100 children in the UK have been affected by a rare inflammatory disease linked to coronavirus, medics say.
Some needed intensive care while others recovered quickly – but cases are extremely rare.
In April, NHS doctors were told to look out for a rare but dangerous reaction in children.
This was prompted by eight children becoming ill in London, including a 14-year-old who died.
Doctors said all eight children had similar symptoms when they were admitted to Evelina London Children’s Hospital, including a high fever, rash, red eyes, swelling and general pain.
Most of the children had no major lung or breathing problems, although seven were put on a ventilator to help improve heart and circulation issues.
Doctors are describing it as a “new phenomenon” similar to Kawasaki disease shock syndrome – a rare condition that mainly affects children under the age of five. Symptoms include a rash, swollen glands in the neck and dry and cracked lips.
But this new syndrome is also affecting older children up to the age of 16, with a minority experiencing serious complications.
Coronavirus: ‘My son had symptoms of rare syndrome’
Dr Liz Whittaker, clinical lecturer in paediatric infectious diseases and immunology, at Imperial College London, said the fact that the syndrome was occurring in the middle of a pandemic, suggests the two are linked.
“You’ve got the Covid-19 peak, and then three or four weeks later we’re seeing a peak in this new phenomenon which makes us think that it’s a post-infectious phenomenon,” she said.
This means it is likely to be something related to the build up of antibodies after infection.
Prof Russell Viner, president of the Royal College of Paediatrics and Child Health, said the majority of children who have had the condition have responded to treatment and are getting better and starting to go home.
The syndrome is “exceptionally rare”, he said.
“This shouldn’t stop parents letting their children exit lockdown,” Prof Viner added.
He said understanding more about the inflammatory disease “might explain why some children become very ill with Covid-19, while the majority are unaffected or asymptomatic”.
Children are thought to make up just 1-2% of all cases of coronavirus infection, accounting for less than 500 admissions to hospital.
Michael Levin, professor of paediatrics and international child health at Imperial, explained that most of the children tested negative for coronavirus, but tested positive for detection of antibodies.
“So we really think that the biology of the disease, somehow involves an unusual immune response to the virus,” he said.
However Prof Levin said there was “a vast amount to learn” about the reaction, which had only been known about for two to three weeks.
Children appear to be affected up to six weeks after they have been infected with the virus, which could explain the appearance of the new syndrome several weeks after the peak of UK cases.
There have been similar cases in the US, Spain, Italy, France and the Netherlands.
Child health experts in the UK say it may not be something which just affects children.
They are now working with researchers in the US and across Europe to find out more about what they have called paediatric inflammatory multisystem syndrome or (PIMS-TS).
US officials investigating link
At least 15 US states are also looking into the rare condition, according to New York governor Andrew Cuomo.
Out of 82 diagnosed cases of the inflammatory syndrome in New York, 53 children tested positive or had antibodies for Covid-19.
California, New Jersey, Connecticut and Massachusetts are among the other states with cases of the syndrome.
The Centers for Disease Control (CDC) in the US is set to issue an alert and updated definition of the syndrome to healthcare providers this week.