But now a growing number of children and teens with even asymptomatic Covid-19 are experiencing long-term effects – sometimes many months after first becoming ill.
And while the data on children is scarce, doctors are finding long Covid in the young to be just as puzzling as it is in adults.
"We can definitely say that children get long Covid," said Dr Elaine Maxwell of the UK National Institute for Health Research in an interview with the Guardian. "But the problem with long Covid is that it's not one definition."
Children are reporting a host of lingering ailments – even if their initial symptoms were mild – including headache, muscle aches, fatigue, heart palpitations, gastrointestinal problems, nausea, dizziness, seizures, memory loss, hallucinations and other sensory symptoms like the loss of sense of taste and smell, and even numbness that leaves children unable to walk.
Some children and teens report struggling to perform everyday activities.
Aarati Kasturirangan, who lives in the US state of Pennsylvania, knows the challenges all too well. Her son Eli was 10 when he caught Covid-19 along with the rest of the family in March 2020.
"He's a bouncy kid normally, but Eli wouldn't come out of his room," Kasturirangan told FRANCE 24 of the weeks and months that followed.
His symptoms were debilitating: pain in his legs so bad he couldn't walk anywhere and gastrointestinal distress and nausea so severe he had to lie in bed. Unable to navigate stairs, he crawled instead. He also had an elevated temperature for weeks, but not high enough for doctors to be alarmed.
"I thought, that's not how it's supposed to be."
In September last year, after a series of tests and visits to specialists, he was formally diagnosed with post-viral fatigue.
"The GI (gastrointestinal) doctor was the most willing to call it long Covid, telling us, 'Yeah it probably is, but we don't know enough yet'. We were told there was nothing that could be done but that it would take time."
At school, basic math equations and completing homework assignments became enormously challenging for the usually grade-A student. Kasturirangan describes it as a "kind of confusion, because he couldn't grasp basic things that he'd normally find so easy to deal with".
She credits the school nurse for helping Eli turn a corner after she came up with a study plan that allowed him to work for one hour virtually and then rest for the next, so he could manage his energy.
'Worrying' numbers
Dr Avindra Nath, chief of nervous system infections at the National Institute of Neurological Disorders and Stroke, told the New York Times that the potential impact on school kids is "huge".
"I mean, they're in their formative years," Nath said. "Once you start falling behind, it's very hard because the kids lose their own self-confidence too. It's a downward spiral."
A UK study by the Office for National Statistics published on August 5 estimated that 0.47 percent of young people between the ages of 12 and 16 had self-reported long Covid, while 0.3 percent of young people in the same age group said their symptoms had limited their activity either "a little" or "a lot".
"Although long Covid in children and young people is less common than in adults, the estimated numbers of those disabled by self-reported long Covid is worrying," said Professor Esther Crenshaw, a specialist in child health at the UK's University of Bristol, in response to the study.
Crenshaw noted that the number of children and young people with long Covid is only likely to increase as case numbers go up.
Long Covid Kids, a UK-based advocacy group supporting children and teens with long Covid, has 3,500 members ranging in age from seven months to 18 years. Its founder Sammie Mcfarland set up the group when her 15-year-old daughter's health deteriorated after contracting Covid-19 in March 2020.
"She went very floppy and almost couldn't make it back into the house to bed," said Mcfarland at a UK parliamentary briefing on January 26. "And she pretty much stayed there (in bed) for the next seven months."
Until now the pandemic has largely focused on preventing severe illness and deaths in older people, many of whom have now been vaccinated. But many advocates, like Mcfarland, and medical experts want to see more attention paid to the young.
Last week paediatric Covid-19 cases accounted for the largest percentage of new infections since the start of the pandemic, according to the American Academy of Pediatrics, with 94,000 new cases registered (15 percent of all cases, up from 14.3 percent on average) in the week ending August 5.
"Simply stated, the Delta variant has created a new and pressing risk to children and adolescents across the country," the academy said in a letter to the US Food and Drug Administration, urging vaccine approvals be expedited for those under 12.
Lack of data
Just how many children might be afflicted with long Covid, and for how long, remains unclear given the few studies available.
Danilo Buonsenso, a paediatrician from Gemelli University Hospital in Rome, is the most-cited researcher on long Covid in children after having been the first to study the phenomenon.
He and his colleagues studied 129 children from between 6 and 16 years of age who were diagnosed with Covid-19 between March and November 2020. The study, published in a peer-reviewed journal in April, found that more than a third of the participants had one or two lingering symptoms four months or more after infection – and another quarter had three or more symptoms.
Among the symptoms children reported were insomnia, fatigue, muscle pain and persistent cold-like complaints — a pattern similar to that seen in adults with long Covid.
"Long Covid is much more rare in children, which is good news," he told the Guardian. "But it's still real."
In April the US National Institutes of Health cited one study suggesting that between 11 percent and 15 percent of infected youths might "end up with this long-term consequence".
The lack of data – which is due, in part, to the delays involved in securing the approval to study children – has contributed to skepticism.
Struggling to be heard
"We are still at the stage where some people are saying that children don't have long Covid," Maxwell told the Guardian.
Differentiating long Covid from other conditions – particularly when many of the symptoms like fatigue, headache, inability to focus can be attributed to any number of other illnesses – is one of the biggest challenges for health professionals and sufferers alike.
According to the sceptics, some symptoms may also be a sign of mental distress, cases of which soared during the pandemic when isolation, social distancing and other restrictions were imposed en masse.
Questions over whether some of the symptoms might be psychological gained traction after a US study of 2 million insurance claims from the organisation Fair Health found that under-18s were more likely to report intestinal issues and "adjustment disorders" described as emotional or behavioural reactions to stressful life events.
The struggle to be heard is, at times, exacerbated for children who report feeling symptoms that do not always show up on medical tests.
In adults, CT scans and blood tests will show certain abnormalities. But in children, tests are showing no abnormalities "and yet they're clearly impaired", said Dr Alicia Johnston, head of the Covid clinic at Boston Children's Hospital, which has treated 40 young patients with long Covid, in an interview with STAT, an online health journal.
Jakob Armann, a paediatrician at Dresden University of Technology in Germany, is among the sceptics, believing that there may be fewer cases of long Covid in children than some of the studies suggest.
But he concedes that even if 10 or 15 percent of the children infected with Covid turn out to have long-term symptoms, "that's a true problem. So this needs to be studied," he told Nature magazine.
Buonsenso disputes the theory that psychological factors are a major cause of long Covid. If that were the case, he argues in Nature, there would have been more long Covid during the first wave in Italy in 2020 when restrictions were even tougher.
Long Covid clinics for kids
A review by the UK National Institute for Health Research suggests that long Covid in adults could also be a number of different syndromes, including post-intensive-care syndrome and post-viral fatigue syndrome, both of which also affect children.
For those with long Covid and their families, such labels do little to ease the burden and distress of living every day with so much uncertainty.
In recent months, however, Kasturirangan has had more reason to be optimistic. On a good day, Eli can go out to the park and play with a friend, and he can sometimes manage to walk more than one block.
"The good days are better than they were before and maybe the bad days aren't as bad," said Kasturirangan. "I can see progress, but it's been so incrementally slow."
Making progress on research into long Covid is also critical.
"We certainly don't have enough data on the long-term impacts of Covid in children to make good policy decisions right now," said Dr Natalie Lambert, director of research for Survivor Corps, the largest Covid-19 advocacy group in the world.
However, many governments are taking steps to recognise long Covid despite the absence of widespread data for children and young adults.
The British government announced in June it would roll out 15 paediatric clinics for children and teens with long-term Covid symptoms under its National Health Service (NHS). Similar clinics exist in the US.
Vaccinating under-18s is part of the solution – as has been the policy in the US, which is finishing vaccine trials for those under 12. In the UK only those over 16 are eligible for the jab while children in the EU are eligible starting at 12.
"I believe in public health interventions and vaccinations is one way we can squash this disease," said Kasturirangan. "And whenever I can, I'm going to talk about my experience because I don't want anyone going through what we did last year. It's taken a toll on us as a family, and what's frightening is we don't know how long we'll have to live with this."
