Over a thousand children, mostly under the age of five, have been diagnosed with mysterious liver problems in the past few months, and now experts from Great Britain believe they have identified the reason why.
Over thirty countries have reported cases of a form of hepatitis, and several dozen children have needed a liver transplant as a result.
Now two teams of researchers, from London and Glasgow, have concluded that COVID restrictions, and specifically lockdowns, are to blame for usually mild viruses resulting in serious illness. The viruses concerned are adenovirus, which normally causes colds and stomach ache, and adeno-associated virus two, which does not ordinarily produce symptoms, and can only replicate in the presence of a "helper virus."
Scientists have ruled out either COVID infection itself or adverse reactions to COVID vaccines as the cause of these cases of child hepatitis, and have concluded that lack of exposure in the early years of life to common viruses has had serious effects on the way children build up their immune systems.
The BBC interviewed several parents of children who have been seriously affected by this phenomenon. One is Noah, three years of age, who has undergone a liver transplant and will now need to take immunosuppressant drugs for the rest of his life.
"There is something really heartbreaking about that because you go along following the rules, do what you are supposed to do to protect people that are vulnerable and then, in some horrible roundabout way, your own child has become more vulnerable because you did what you were supposed to do," his mother said.
Professor Judith Breuer, an expert virologist at University College London and Great Ormond Street Hospital, told the BBC that, "During the lockdown period when children were not mixing, they were not transmitting viruses to each other. They were not building up immunity to the common infections they would normally encounter.
"When the restrictions were lifted, children began to mix, viruses began to circulate freely - and they suddenly were exposed with this lack of prior immunity to a whole battery of new infections."
Experts are hopeful that cases are now becoming fewer but they remain on alert for any new resurgences.