Previous estimates have suggested that the number could be anywhere between 16 percent and 45 percent.
The research, which examined more than 2,400 children who were tested for the virus between April and September, also contended that the number of children diagnosed with the disease may represent only a fraction of those actually infected.
“The concern from a public health perspective is that there is probably a lot of COVID-19 circulating in the community that people don’t even realize,” Finlay McAlister, a professor of medicine at the University of Alberta, said in a news release.
“When we see reports of 1,200 new cases per day in Alberta, that’s likely just the tip of the iceberg—there are likely many people who don’t know they have the disease and are potentially spreading it.”
In the United States, more than 1.3 million children have been diagnosed with coronavirus.
For the study, the researchers analyzed results of 2,463 children who were tested during the first wave of the pandemic. In all, 1,987 children had tests that came back positive, and 714 of them—or 35.9 percent—reported being asymptomatic.
“It speaks to the school safety programs,” McAlister said. “We can do all the COVID-19 questionnaires we want, but if one-third of the kids are asymptomatic, the answer is going to be no to all the questions—yet they’re still infected.”
The researchers also discovered that cough, runny nose, and sore throat were three of the most common coronavirus symptoms among children—showing up in 25, 19, and 16 percent of cases, respectively. However, these particular symptoms were actually slightly more common among those who tested negative for the coronavirus.
“Of course, kids are at risk of contracting many different viruses, so the COVID-specific symptoms are actually more things like loss of taste and smell, headache, fever, and nausea and vomiting—not runny nose, a cough, and sore throat,” McAlister said.
Recent data is pointing toward the fact that elementary and high schools do not appear to be the “super-spreaders” they were once feared to be, but they are still vulnerable to undetected spread of the virus if a significant percentage of children are asymptomatic carriers.
Therefore, McAlister believes that the province made the right call when it decided to close schools for a longer period over the Christmas holiday.
“As far as we know, kids are less likely to spread disease than adults, but the risk is not zero,” he said. “Presumably, asymptomatic spreaders are less contagious than the person sitting nearby who is sneezing all over you, but we don’t know that for sure.”
Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.