Children can carry coronavirus in their noses for up to three weeks, according to a study.
The South Korean report, based on 91 children, found that the virus could be found in their noses for up to three weeks, even if they have no or few symptoms.
Authors of the report suggest that children could pass Covid-19 on to others, and it could explain how it spreads silently.
Among the 91 children that were included in the study, 20 of them did not show any obvious symptoms and remained asymptomatic throughout the study.
Another 18 children were presymptomatic, meaning they didn’t look or feel sick at the time but eventually got symptoms later.
But 71 of them in total did show symptoms, including fever, cough, diarrhea, abdominal pain and loss of smell or taste.
The researchers, from the Seoul National University College of Medicine, said: “In this case series study, inapparent infections in children may have been associated with silent COVID-19 transmission in the community.”
They highlighted the importance of contact tracing to isolate children as soon as possible so they don’t spread coronavirus in the community.
The children, who were tested from 22 hospital across South Korea, were monitored for 21 days, with the virus detected for around two-and-a-half weeks.
But at least half of those symptomatic were still showing traces of the virus for three weeks.
Dr. Roberta DeBiasi and Dr. Meghan Delaney, both of Children’s National Hospital in Washington, DC, wrote an editorial about the study.
The pair wrote: “This highlights the concept that infected children may be more likely to go unnoticed either with or without symptoms and continue on with their usual activities, which may contribute to viral circulation within their community.
“This suggests that even mild and moderately affected children remain symptomatic for long periods of time.”
It comes as a separate study revealed that not a single healthy child has died from the disease in the UK.
Research shows the six deaths that have occurred were those suffering from serious illness or underlying health disorders.
In the largest study in the world examining children hospitalised with Covid-19, researchers examined the characteristics of youngsters admitted to hospital and those who have severe disease.
Of patients admitted to 138 hospitals in Britain found that less than 1 per cent were children.
They stressed the risk to minors being admitted to hospital is “tiny” and the risk of needing critical care is “even tinier”.
While the overall numbers were small, the team were able to identify which children were more likely to need critical care support in hospital – including newborns under the age of one month, children aged 10 to 14, black children and children who are obese.
They were able to identify a “cluster” of symptoms linked to the hyper-inflammatory response to Covid-19 seen in a small number of children – which are slightly different to those currently known in the medical community.
Six children died in the study, all of whom had “profound comorbidities”, which means having more than one condition or disease at the same time.
“Severe disease is rare and death is vanishingly rare,” said Calum Semple, professor of child health and outbreak medicine at the University of Liverpool.
“They should be confident that their children are not going to be put at direct harm by going back to school and we do know that they are harm by being kept away from school because of the lack of educational opportunities, and that’s affecting mental health.”