Children May Be 'Important Drivers' in Coronavirus Spread, Scientists Say

Children under the age of five with the coronavirus have been found to have more traces of the germ in their noses than older kids and adults in a study.

The paper comes amid a debate in the U.S. about when and how children should go back to in-person learning in classrooms, with evidence showing that although COVID-19 is milder in younger children, with some showing no symptoms, they are still able to spread it.

The research letter published in the journal JAMA Pediatrics involved 145 people with mild to moderate COVID-19 from Chicago, who were tested for the coronavirus between March 23 and April 27, 2020, one week after their symptoms started.

The participants were split into three groups: 46 children under five years old, 51 between 5-17 years old, and 48 adults aged between 18-65.

On average, similar levels of the virus genetic material, or RNA, were found in the samples from the older children and adults. But significantly more was found in the under-fives—at approximately 10 to 100 greater amounts.

The team said their study was limited because they were looking for the virus's genetic material from the samples, rather than the infectious virus. But they said past studies have shown scientists are better able to culture the virus in a lab from samples containing more genetic material.

Children may therefore potentially be "important drivers" in the spread of the coronavirus in the general population, they said, as is the case with respiratory syncytial virus where this group carry higher viral loads and are more likely to pass it on.

Andrew Preston, who researches microbial pathogenesis at the U.K.'s University of Bath and did not work on the paper, told Newsweek via email the study was "interesting" but "raises more questions that it answers."

Preston said genetic material, or RNA, being present is not a measure of infectiousness, as it can include both viral particles, debris from dead viruses, or infected cells.

As children are less likely to get ill, it may be the case the children included in the study are a "skewed sample," Preston said. "Ill people are more likely to have higher levels of virus. By including only ill children it is likely to bias towards the small percentage of infected children that suffer high viral levels."

Preston said: "To address the question of whether children are important transmitters of infection, a much broader representation of these age groups is required. This study might suggest (subject to the caveat above about the distinction between viral RNA and infectious viral particles) that children who become ill with COVID-19 can transmit the infection to others, but that is very different from saying that children in general are or are not important to transmission."

Ian Jones, professor of virology at the U.K.'s University of Reading who also did not work on the paper, told Newsweek the results are surprising as a separate study published in the journal JAMA in May suggested that children may be less likely to be infected with the coronavirus because they have lower levels of the receptor it uses to enter our bodies, called ACE2.

"Whether the higher levels reported here resulted in higher transmission was not tested and other factors, such as how hard they sneeze, if at all, and how long the infection lasts, will have a role to play," he said.

"Overall the relative role of children as spreaders of community acquired COVID-19 will need more analysis but it's clear from studies like these that we cannot assume that mild symptoms means little or no virus."

Jeremy Rossman, honorary senior lecturer in virology at the University of Kent who was not involved in the study, told Newsweek: "This is a very interesting study with some very concerning implications."

He said: "It is possible, though unlikely, that young children have high levels of viral RNA but still don't transmit the virus as effectively as adults. These results have significant implications as many countries faces school reopenings."

This article has been updated with comment from Jeremy Rossman.

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A stock image shows a child wiping her nose. Getty