Two new coronavirus symptoms have been reported in children that haven't been prevalent in adults.
A new study has found that diarrhoea and vomiting are the most common symptoms of Covid-19 in children - ahead of a persistent cough and changes to their senses of taste and smell.
Cardiff and Vale University Health Board has taken part in a UK-wide study that gives fresh insight into common symptoms and the prevalence of coronavirus in children.
More than 1,000 children across the UK have taken part so far, reports Wales Online.
Since the study started in May, 7% of the children who participated tested positive for antibodies which indicate previous Covid-19 infection. More than half of the children who had the virus reported no symptoms whatsoever.
Researchers found that gastrointestinal symptoms - such as diarrhoea and vomiting - were the most common symptoms of the virus in children, ahead of cough or changes in their sense of smell or taste.
The findings also showed that those under 10 were just as likely to have evidence of prior infection as older children, and that children without symptoms were just as likely to develop antibodies as children with symptoms.
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Paediatric research nurse specialist Zoe Morrison said: "Thanks to this study we now better understand the prevalence of Covid-19 in children after the first wave of the pandemic, and know that while the majority of children with Covid-19 will display no symptoms.
"Gastrointestinal symptoms such as diarrhoea and vomiting could be a sign that they are infected with the disease and must now consider the value of refining the testing criteria for children to include these symptoms.
"The interest in participating in this clinical trial has been unprecedented and we would like to extend our thanks to all the children and their parents who have volunteered to take part in this study, helping us gain important insight into how this virus behaves among children."
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The health board's Children and Young Adult’s Research Unit (CYARU) has been implementing the so-called "Rapid-19" study.
Fiona Kinghorn, executive director of Public Health for Cardiff and Vale University Health Board, said: "Covid-19 remains a relatively new virus to us, and it is important that through valuable research studies such as this we continue to increase our understanding of it.
"I would like to thank my research colleagues here at Cardiff and Vale UHB for their excellent contribution to this study, and congratulate everybody involved for their role in these important findings as this research continues to monitor community transmission of the virus in children."
The team will also be using samples collected during the study to test the efficacy of new antibody tests that are developed, as well as monitoring the longer-term behavior of the antibodies to understand whether they reduce in numbers or if children can lose them over time.
