Enlarge / A prepandemic summer camp, showing many things that go against current public health guidance.Educational Images

It has become abundantly clear that children tend to have less severe cases of COVID-19 and often experience no symptoms whatsoever. That doesn't mean that there's no risk—some kids clearly get severely ill, and some have died. But if the risks of reopening schools were based only on the symptoms experienced by children, then the evaluation would be relatively simple. But the risk evaluation is substantially more complex than that, since children can potentially spread the virus, even if they themselves do not experience symptoms. And those to whom they spread coronavirus, such as teachers and school support staff, may be at much higher risk of severe illness.

Some studies of the virus' spread early on in the COVID-19 pandemic suggested that children resisted infection, but that hasn't been seen in every study. Now, some new reports are complicating matters even further. Two studies show that children may actually carry higher levels of the virus than adults. And another one indicates that the virus spread rapidly in a youth summer camp, an environment that may have some semblance to schools.

Lots of virus

While there are many factors that go into determining viral spread, the presence of the virus is an essential one. So a couple of groups has decided to look at how large a viral load children carry. One of these groups involved researchers who cooperated with people running testing centers in Germany, examining the 3,300 people who tested positive for SARS-CoV-2 out of 78,000 tests the groups had run. This included the early days of the rising pandemic, as well as after falling rates of infection lowered the frequency of testing.

The type of test used (based on real-time RT-PCR) is able to not only tell us whether the virus is present but also the speed with which the positive test becomes clear. It also gives us a rough measure of how much virus is present. The researchers could compare this level to their earlier work, which had identified a threshold in this assay at which there was a greater than 5 percent chance that they could isolate infectious viruses from the person testing positive.

Based on that standard, 29 percent of those under seven years of age were potentially infectious. That contrasts to 37 percent of those under 20 and half of those aged 20 and older. At the earlier stages of the pandemic, testing indicated that there was no significant differences among the age groups, suggesting that at least part of the difference is due to how the tests were being used. In any case, however, the authors suggest that the study provides clear evidence that young children have the potential to pass the virus on to others.

While that study hasn't made it through peer review yet, a similar one was published in JAMA Pediatrics. This work, done by a group of researchers in Chicago, relied on a combination of results from drive-up testing and tests in a hospital. The Chicago researchers selected people who had a mild to moderate illness due to their SARS-CoV-2 infection, which limited them to just under 150 participants. Real-time RT-PCR testing was used in this case as well. Rather than a threshold based on a measure of infectivity, they simply registered how quickly the assay produced a positive result.

But these researchers saw something different from their peers in Germany. Here, younger patients, defined as children under six years of age, had the highest levels of virus. Those under 18 were next, having values similar to adults 18 years and older. Based on the dynamics of the RT-PCR reaction, the researchers estimate that this indicates that young children have between 10 and 100 times more virus than their older peers. While there are differences between this and the other results, the implications of both are consistent: we can't assume that children don't pose a risk of transmitting the infection.

It's important to note that neither of these studies looked at viable virus; there's a chance that these results came from viral debris rather than functional viruses. The results are also limited by who was chosen to be tested: limited testing at the early stages of the pandemic (or within the United States in general) may mean that symptomatic children were more likely to be tested. If a higher viral load correlates with more severe symptoms, then it's possible that the testing situation selected for children with more virus.

A dry run for schools?

In the face of these uncertainties, both papers emphasize a critical point: most societies shut their schools down as the pandemic's threat became apparent, which has kept schools from driving COVID-19's spread. While that's contributing to our limited understanding of the risks of reopening them, there have been a number of cases where SARS-CoV-2 has spread rapidly among young people, providing opportunities to trace the viruses' behavior in this population. One of those was described by the Centers for Disease Control last week.

The report focuses on a summer camp in Georgia that briefly hosted children in June before sending everyone home as SARS-CoV-2 ripped through the population. The format of the camp sounds, well, like an invitation to disaster. Prior to the arrival of the kids, the 120 camp staff members held a three-day orientation session for 138 trainees. Those future staff members then left, at which point 363 younger children showed up at the camp. While the staff was required to submit SARS-CoV-2 testing resulRead More – Source

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