New COVID-19 Study Shows Teens Spread the Virus as Fast as Adults


Getty This photo from the Centers for Disease Control and Prevention (CDC) shows a microscopic view of the Coronavirus.

A new study argues that teens and tweens are the fastest spreaders of COVID-19 within juveniles, and they spread it as fast as adults do. The study makes an argument for school closures to slow transmission of the virus. The findings emerged as school districts throughout the United States are trying to decide whether to hold in-person classes in the fall.

An early release version of the study, which is due in full in October 2020, was published in July on the website of the U.S. Centers for Disease Control and Prevention. You can see the study here.

“We analyzed reports for 59,073 contacts of 5,706 coronavirus disease (COVID-19) index patients reported in South Korea during January 20–March 27, 2020. Of 10,592 household contacts, 11.8% had COVID-19,” the researchers wrote. “Of 48,481 nonhousehold contacts, 1.9% had COVID-19. Use of personal protective measures and social distancing reduces the likelihood of transmission.”

The study concluded:

We showed that household transmission of SARS-CoV-2 was high if the index patient was 10–19 years of age. In the current mitigation strategy that includes physical distancing, optimizing the likelihood of reducing individual, family, and community disease is important. Implementation of public health recommendations, including hand and respiratory hygiene, should be encouraged to reduce transmission of SARS-CoV-2 within affected households.

The New York Times summarized the findings this way: “Children younger than 10 transmit to others much less often than adults do, but the risk is not zero. And those between the ages of 10 and 19 can spread the virus at least as well as adults do.”

Here’s what you need to know:

The Study Argues That School Closures Lowered Infection Rates


GettyA model of COVID-19, known as coronavirus, is seen ahead of testimony from Dr. Francis Collins, Director of the National Institutes of Health (NIH), during a US Senate Appropriations subcommittee hearing on the plan to research, manufacture and distribute a coronavirus vaccine, known as Operation Warp Speed, July 2, 2020.

“Our large-scale investigation showed that pattern of transmission was similar to those of other respiratory viruses,” the researchers wrote. “Although the detection rate for contacts of preschool-aged children was lower, young children may show higher attack rates when the school closure ends, contributing to community transmission of COVID-19.”

The study “detected COVID-19 in 11.8% of household contacts; rates were higher for contacts of children than adults. These risks largely reflected transmission in the middle of mitigation and therefore might characterize transmission dynamics during school closure.”

According to The Times, experts praised “the scale and rigor of the analysis,” in contrast to earlier studies that found children are less likely to spread COVID-19.

The Virus Spread More Inside Households Than Outside of Them, the Study Found

The study found “higher household than nonhousehold detection,” which “might partly reflect transmission during social distancing, when family members largely stayed home except to perform essential tasks, possibly creating spread within the household.”

According to the researchers, studies have found that COVID-19 spreads to more people inside households than outside of them. There are variations in different countries. “Given the high infection rate within families, personal protective measures should be used at home to reduce the risk for transmission. If feasible, cohort isolation outside of hospitals, such as in a Community Treatment Center, might be a viable option for managing household transmission,” the study found.

“We also found the highest COVID-19 rate (18.6% [95% CI 14.0%–24.0%]) for household contacts of school-aged children and the lowest (5.3% [95% CI 1.3%–13.7%]) for household contacts of children 0–9 years in the middle of school closure,” the study found. It made an argument for school closure:

Despite closure of their schools, these children might have interacted with each other, although we do not have data to support that hypothesis. A contact survey in Wuhan and Shanghai, China, showed that school closure and social distancing significantly reduced the rate of COVID-19 among contacts of school-aged children. In the case of seasonal influenza epidemics, the highest secondary attack rate occurs among young children. Children who attend day care or school also are at high risk for transmitting respiratory viruses to household members. The low detection rate for household contacts of preschool-aged children in South Korea might be attributable to social distancing during these periods. Yet, a recent report from Shenzhen, China, showed that the proportion of infected children increased during the outbreak from 2% to 13%, suggesting the importance of school closure. Further evidence, including serologic studies, is needed to evaluate the public health benefit of school closure as part of mitigation strategies.

“I fear that there has been this sense that kids just won’t get infected or don’t get infected in the same way as adults and that, therefore, they’re almost like a bubbled population,” said Michael Osterholm, an infectious diseases expert at the University of Minnesota, told The Times. “There will be transmission. What we have to do is accept that now and include that in our plans.”

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