Although children were less affected by COVID-19, among those infected majority are likely to develop long COVID similar to adults. However, their condition often remains undiagnosed, the media reported.

It's not clear how many children go on to develop long COVID because there's not enough research on it in this age group. Many parents may also not know their child has long COVID, or the child's paediatrician hasn't recognised it as such, CNN reported.

According to the American Academy of Pediatrics, almost 13 million children have tested positive for COVID in the US alone, since the start of the pandemic. While the global number may not be properly available, studies suggest that between 2 per cent and 10 per cent of infected children will develop long COVID, but the number may be larger.

In March, a preprint study, not peer-reviewed pooled data from 21 studies previously carried out in Europe, Asia, Australia and South America to show that one in four children go on to develop long COVID. In adults, some research puts the number around 30 per cent of cases.

"I personally believe that this is very much an undiagnosed issue," Dr Sara Kristen Sexson Tejtel, from Texas Children's Hospital in Houston, was quoted as saying. Although adults have a definite set of symptoms, including breathlessness, and fatigue among others, the symptoms in children are not clear.

Some kids present conditions such as fatigue, brain fog and severe headaches, "to the point where some aren't able to go to school, grades are failing, those types of issues", Tejtel said.

They also present cardiac issues like heart palpitations, chest pains and dizziness, especially when they go back to their regular activities; stomach problems; and also a change in their sense of taste and smell.

"It's startling how many of these children present and have a range of symptoms that we haven't fully appreciated. Some are coming in with heart failure after asymptomatic COVID infections," Dr Jeffrey Kahn, chief of the Division of Pediatric Infectious Disease at UT Southwestern Medical Center in Dallas, was quoted as saying.

"What's striking to me is that it usually occurs about four weeks after infection, and infection can be really asymptomatic, which is really startling," he added. Further, the report noted experts saying that even when kids with long COVID are tested for ailments that might cause these symptoms, it's possible nothing will show up and all the tests come back normal.

"We also scoped them, and their GI tracts are normal. I do a big immune workup, and their immune system appears normal. Everything 'looks normal,' but the kids aren't functioning like normal," Dr Amy Edwards, who runs the paediatric long COVID clinic at UH Rainbow Babies & Children's Hospital in Cleveland, was quoted as saying.

"I tell the families, 'you have to remember, there are limits to what medical science understands and can test for.' Sometimes, we're just not smart enough to know where to look for it." Edwards said while most healthy people can push through if they're tired, those with long COVID can't.

"It's like they have one bucket of energy, and it has to be used carefully for school, for play, to watch TV. Every single thing they do takes energy, and once that bucket is empty, that's it," she noted.