are young children ultimately more contagious than expected?


According to an American study, young children with Covid-19 carry a significant amount of the virus. Are they contagious for all that? Decryption.

A young child gets tested in Karachi, Pakistan.  (Photo by STR / AFP)

A young child gets tested in Karachi, Pakistan. (Photo by STR / AFP)

Are young children sick with Covid-19 finally contagious? The question was revived by an American study published Thursday in the medical journal JAMA Pediatrics. According to the latter, the rate of genetic material of the coronavirus detected in the noses of children under five years old is 10 to 100 times higher than that found in older children or adults. “Young children can potentially be important factors in the spread of SARS-CoV-2 in the general population,” the researchers say.

A radically different hypothesis from those formulated so far on the contagiousness of children. Indeed, these were quickly considered as relatively little symptomatic and weakly propagating, following several scientific publications in this direction.

Thus last June, a study conducted by the Institut Pasteur in schools in Crepy-en-Valois – a city badly affected during the first wave of infection – concluded that children transmit Covid-19 very little at school. , whether to other students or adults. “Typically, children are infected in families, most often by their parents, but then transmit very little at school,” explained its main author, Arnaud Fontanet, epidemiologist and member of the Scientific Council.

Viral load and contagiousness

Across the Atlantic, the American study was conducted between March 23 and April 27 in Chicago. Researchers conducted nasal swab screening tests on 145 patients, suffering from a mild to moderate form of Covid-19, a week after the onset of their first symptoms. The patients were divided into three groups: 46 children under five, 51 children aged 5 to 17, and 48 adults between 18 and 65.

However, researchers have observed the presence of the SARS-CoV-2 virus in quantities “10 to 100 times greater” than others in the respiratory tracts of young children. “This clearly shows that children have similar and possibly higher levels of the virus than adults,” New York Times Taylor Heald-Sargent, the pediatric infectious disease researcher who led the study published in JAMA Pediatrics. “It would not be surprising if they were able to spread the virus and spread it to others,” she added.

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Still, this hypothesis is not proven at this stage in the work carried out by the researcher. Indeed, the study shows that the viral load is higher in children under 5, but not that they are more contagious. “Viral load and contagiousness are two things that are not necessarily linked. Contagiousness is influenced by viral load, but many other factors come into play”, underlines Daniel Camus, epidemiologist at the Institut Pasteur, contacted by L’Express.

According to the researcher, having a significant amount of the virus therefore does not necessarily mean being more contagious. “Just because you carry a lot of viruses does not mean that you shed a lot of viruses. Children may shed a lot less virus than older people. So viral load does not mechanically involve the virus. contagiousness, ”he explains.

Conflicting studies

In its study carried out in Crepy-en-Valois, the Institut Pasteur had identified three children from three different establishments who were infected with the new coronavirus when schools were still open. However, these three children had not infected anyone at school, whether they were other students or adults. A total of 1340 people (510 children, 76 parents, 42 teachers, plus non-teaching staff and family members) had been tested.

However, beyond the study published by JAMA Pediatrics, another survey has been attracting attention for a few hours. The U.S. Centers for Disease Prevention and Control (CDC) announced on Friday that hundreds of children contracted the coronavirus at summer camp last month in the U.S. state of Georgia. The virus has infected at least 260 of the 597 participants in this summer camp, according to US health authorities. They also indicate that the figure could be higher since the results were only available for 58% of the group.

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“These results demonstrate that SARS-CoV-2 spread effectively in an environment made up of young people, with high attack rates among people of all age groups,” the CDC said. While the holiday camp in question had ignored the recommendation to have every child wear a mask, it had applied the Georgia state decree requiring all participants to test negative for Covid-19, performed at most 12 days before their arrival. “This investigation adds to the body of evidence showing that children of all ages are susceptible to infection with SARS-CoV-2 and that, unlike early reports, they could play an important role in the transmission of the virus.” , conclude the American health authorities.

In this context of uncertainty, Daniel Camus recommends remaining cautious, limiting contact between frail people and children, when the latter show signs of infection. “It is now necessary to verify in new studies whether this significant viral load observed in children can have an impact on their level of contagiousness”, he adds. Research which promises to be decisive in any case, with a view to the start of the school year.

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