A somewhat-mysterious inflammatory syndrome is a rare complication of the coronavirus among children.
Early research suggests the infection is mild in four out of five cases, with the vast majority of critically-ill patients being elderly.
Nevertheless, NHS doctors were told to look out for signs of "multi-system inflammation" after intensive care units in London saw eight children with unusual symptoms, some of whom tested positive for the coronavirus.
The mysterious inflammation has been likened to atypical Kawasaki disease; a rare condition that usually affects children under five and causes blood vessels to become inflamed, leading to heart complications in around a quarter (25%) of patients. Left untreated, it can be fatal in 2% to 3% of cases.
The UK's coronavirus vaccination programme offers hope for the future, with more than 23 million first doses being administered.
With the jabs not yet approved for children, a paediatrician explains how parents can differentiate between multi-system inflammation and Kawasaki disease.
Watch: Coronavirus can cause inflammatory syndrome in children
On 1 May 2020, the Royal College of Paediatrics and Child Health defined so-called "paediatric inflammatory multi-system syndrome temporally associated with coronavirus" as a persistent fever, inflammation and "evidence of single or multi-organ dysfunction".
This could occur alongside or a few weeks after a positive or negative coronavirus test, providing any other "microbial cause" is ruled out.
While cases of the inflammatory syndrome have spiked during the pandemic, not everyone with the condition swabs positive for the coronavirus, which may come down to a false-negative result.
The inflammatory syndrome can cause symptoms that are similar to the more unusual signs of the coronavirus, like diarrhoea, nausea and abdominal cramps.
To better understand how the conditions differ, scientists from Rutgers University in New Jersey compared 539 children with multi-system inflammation to 577 who were hospitalised with the coronavirus.
Results revealed the children with multi-system inflammation were more likely to be aged six to 12 and non-Hispanic Black. They also had "severe cardiovascular or mucocutaneous [skin and mucous membrane] involvement" and "more extreme inflammation".
Like Kawasaki disease, multi-system inflammation can cause severe swelling of the heart, brain, lungs, kidneys and gut.
How multi-system inflammation, Kawasaki disease and COVID-19 differ
While it sounds complex, one of the Rutgers scientists has stressed multi-system inflammation, Kawasaki disease and a severe case of the coronavirus can be differentiated.
"In general, children with MIS-C [multi-system inflammatory syndrome from severe COVID-19] tend to get sicker than those with acute COVID-19 [the disease caused by the coronavirus] since more organs are involved," said Dr Robert Wood.
"While children with acute COVID-19 can have respiratory and gastrointestinal symptoms directly related to the virus, MIS-C seems to be an inflammatory response to the infection that occurs several weeks later, and that can resemble COVID-19."
The Rutgers study revealed four in five (80%) of the children hospitalised with multi-system inflammation or severe coronavirus had serious respiratory symptoms, however, the former was more likely to trigger rashes and red eyes.
Skin symptoms also occur with Kawasaki disease, with red hands and feet being a tell-tale sign of the disorder.
Scientists from the New York University Grossman School of Medicine have previously noted "significant clinical overlap exists" between Kawasaki and coronavirus-related inflammatory syndrome.
The latter, however, "has been characterised by more widespread systemic inflammation and higher rates of acute complications, including cardiogenic shock"; when the heart suddenly cannot pump enough blood to meet the body's needs.
Another differentiator between multi-system inflammation and Kawasaki disease appears to be the ages of the children the conditions affect.
Kawasaki patients tend to be under five, while the Rutgers study flagged older children as being more at risk of multi-system inflammation.
Ultimately, a concerned parent should seek medical help.
"I have children, so I understand how nervous parents are about this new syndrome," said Dr Wood.
"If your child develops a multitude of symptoms such as persistent fevers or rash or seems unusually tired, have your child assessed by a medical professional to rule out MIS-C.
"While MIS-C is a serious condition, most children including those with severe cardiac symptoms, usually recover within 30 days."
The Royal College of Paediatrics and Child Health previously advised parents call 999 or take their child to A&E if they:
Become pale, mottled or abnormally cold to touch
Pause in their breathing, have an irregular breathing pattern or grunt
Have severe breathing difficulties, while becoming agitated or unresponsive
Go blue around the lips
Have a seizure
Become extremely distressed, confused, lethargic or unresponsive
Develop a rash that does not disappear with pressure, like when pressed under a glass
Have testicular pain, especially teenagers
Great Ormond Street Hospital has also flagged fatigue, red or cracked lips, swelling and peeling of the hands and feet, headaches, swollen lymph nodes in the neck, and unexplained irritability as symptoms of coronavirus-related inflammation.
Watch: Why are children less at risk of coronavirus?