Children under the age of five have 10 to 100-fold higher levels of coronavirus genetic material between their noses than older children and adults, according to the JAMA Pediatrics study.
Its authors have written that this means that young children can be important drivers of Covid-19 transmission in communities – contrary to the current prevailing storytelling.
The document comes as US administration Donald Trump’s administration presses hard to reopen schools and kindergartens to kick-start the economy.
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Between March 23 and April 27, researchers performed nasal swab tests on 145 patients from Chicago with mild to moderate disease within one week of the onset of symptoms.
The patients were divided into three groups: 46 children under the age of five, 51children aged 5 to 17 years and 48 adults aged 18 to 65 years.
A team led by Dr. Taylor Heald-Sargent of Ann & Robert H. Lurie Children’s Hospital observed “10- to 100-fold greater SARS-CoV-2 in the upper airways of young children.”
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The authors added that a recent laboratory study showed that the more viral genetic material, the more infectious the virus can be grown.
It has previously been shown that children with a high viral load of respiratory syncytial virus (RSV) are more likely to spread the disease.
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“Young children can thus be potentially important factors in the spread of SARS-CoV-2 in the general population,” the authors wrote.
“The behavioral habits of young children and nearby neighborhoods in school and day care facilities raise concerns in this population about the strengthening of SARS-CoV-2 as public health restrictions are eased,” they concluded.
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The new findings contradict the current view of health authorities that young children – who are well known to be much less prone to serious viral illness – do not extend it too much to others.
So far, however, relatively little research has been done in this area.
A recent study in South Korea found that children between the ages of 10 and 19 transmitted the Covid-19 program in households in the same way as adults, but children under the age of nine transmitted the virus at a lower rate.