Coronavirus: Children as a mirror of the adult world

In no age group is the 7-day incidence per 100,000 inhabitants in Germany currently higher than among 15 to 24-year-olds and five to 14-year-olds. Something similar can currently be observed in the United Kingdom and Italy, for example. The virus variant B.1.1.7, which was first discovered in the south of England, is circulating heavily in both countries. “The British variant has the particular ability to spread widely among the younger generation,” said Italy’s Minister of Health Roberto Speranza. In regions that are particularly affected by the pathogen – the “red zones” – schools will remain temporarily closed until April 6th.

Whether B.1.1.7 actually affects children and adolescents more than adults has not yet been scientifically clarified, says the microbiologist Michael Wagner from the University of Vienna to ORF.at. Wagner is the scientific coordinator of the PCR-Gurgelstudie, the third round of which has been running in Austrian schools since last week. According to Wagner, the first two rounds carried out in autumn showed that children and adolescents have a similarly high viral load in their throats as teachers. “If we take the six to 14-year-olds together, the viral load on average is not different from that of the teachers,” says Wagner. In younger children, on the other hand, slightly lower viral loads were measured than in older children.

Transmission: Viral load is just one of several factors

The findings coincide with the results of international studies. A CoV infection is more often asymptomatic in children than in adults. However, they can still carry large amounts of the virus. A recently published study from Spain concluded that the viral load in infected children was as high as in adults. And: There were no differences between asymptomatic and symptomatic in terms of viral load.

“There is no doubt that children can be contagious,” says Wagner, “the question is how contagious.” The viral load is just one of many factors in the transmission of the pathogen. The strength of the aerosol and droplet emission is also decisive. “That varies extremely even with adults,” says Wagner. Aerosols with infectious material do not only get into the air when sneezing or coughing. Loud singing and screaming – as children like to do – also increase emissions. However, children have a smaller respiratory volume, which in turn can dampen the release of suspended particles.

Who infects whom

The following applies to adults: 20 percent of those infected with CoV are responsible for 80 percent of infections. They are known under the term “superspreader”, with consistent contact tracing they can be found in many cases. Identifying a child as the starting point of a chain of infection, on the other hand, is much more difficult.

Since the infection is often asymptomatic in children, it can infect the parents unnoticed. By the time the disease becomes noticeable in the adults, they are tested and contact tracing starts, the PCR test in the children could already be negative, says Wagner: “Then it is even said that they are not infected.”

One available as a preprint study The Danish State Disease Protection Agency (SSI) with data from more than three million people came to the conclusion that the risk of coronavirus infection increases with every child living in a household. Wagner advocates carrying out “household studies” in Austria in order to shed light on the darkness. In practice, this means that if a child is discovered by chance with an asymptomatic infection, everyone living in the household must be tested over a period of several weeks.

1,472 positives in “nose drill tests”

On February 8, schools in Germany resumed classroom teaching. Regular antigen self-tests in the anterior nasal region, better known as “nose bur tests”, are a prerequisite for attending school. Elementary school pupils no longer have to take the tests twice a week from March 15, but three times a week. The remaining schools work in shifts, with two days of face-to-face and two days of distance learning (on Friday all have distance learning).

Last week, 1.4 million rapid tests were carried out in Austria’s schools. 1,274 of these were positive (840 for children and adolescents, 407 for teaching and administrative staff). This corresponds to about 0.09 percent of those tested. The most cases in absolute terms were discovered during the self-tests this week in Vienna (429), followed by Lower Austria (209), Upper Austria (161), and the fewest in Vorarlberg (19). The Ministry of Education told the APA that 13 of the total of 5,800 Austrian schools were sent to distance learning after positive quick tests.

Compared to the previous weeks, the numbers have risen again. Most recently there were around 900 positive test results, in calendar week seven there were around 500. The Ministry of Education and experts from the Austrian Society for Pediatrics and Adolescent Medicine (ÖGKJ), who scientifically support the screening, partly led to the increase compared to the APA Infection incidence in the entire society back. In addition, the more practiced the students would become better at taking samples.

Antigen tests with limited informative value

Wagner sees the antigen school tests as positive, but points out the limits of the meaningfulness of the tests used. With the help of the rapid tests, many, but not all, “really highly infectious” people could be filtered out. Compulsory testing also means that children from less health-conscious social classes can be reached, in whom parents may use the public test offers less often. However, the rapid antigen tests are much less sensitive than the PCR tests used in the Gurgel study. Infected and also infectious people could slip through the grid, says Wagner.

During the PCR, virus components are searched for in the laboratory. The pathogen can be detected with this method as early as the third or fourth day after infection. At this point in time, those affected usually have no symptoms, but they can already be infectious. Rapid antigen tests, on the other hand, work most reliably on the fifth or sixth day; shortly before or more often shortly after the first signs of illness appear.

If the rapid antigen test is positive, two lines appear 15 minutes after applying the sample. According to Wagner, it is essential to wait for this 15-minute period. Even if the second line appears very weak, the result could be positive, according to the scientist. The advantages of the rapid tests are the reduced effort and the quick results. In the case of PCR, including logistics and evaluation, it usually takes a day before the result is available.

Mirror, not “engine”

After evaluating CoV outbreaks in schools, the German Robert Koch Institute came to the cautious conclusion that schoolchildren “tend not to play a greater role as the ‘engine’” of the pandemic. The “frequency” with which school clusters occur is “closely related to the incidence in the general population”. “Children reflect the infection rate in the general population,” says Wagner, who refers to the results of the second round of the gargle study in autumn. The infection rate in schools and in the general Austrian population was on a similar scale at that time.

If you want to keep the schools open permanently and forego shift work, you have to adapt the current test concept. Wherever logistically possible, gargle PCR tests should be carried out three times per week. Currently, classes in elementary schools are not quarantined if only one child is infected. According to Wagner – as with adults – if a case occurs, the child’s environment should also be tested.

In general, “classes should be tested with Gurgel-PCR at least twice with an interval of a few days in positive cases”. Of course, a lot depends on how the numbers develop. A clear increase has been seen since the beginning of February, with the incidence approaching the 200 mark nationwide. “If we run into very high numbers in Austria, I don’t think we can keep the schools open,” says Wagner, “but I hope that through consistent testing and avoiding further opening steps – as long as the incidence does not fall significantly – it can be manages not to have to close it again. “

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