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Are Kids Really ‘Super Spreaders’ of COVID-19?

Are Kids Really ‘Super Spreaders’ of COVID-19?

Kids aren’t immune to COVID-19 and they can spread it, but research doesn’t show they’re driving the pandemic. Here’s why.

Updated on September 11, 2020 at 12:00pm EDT.

Early on, researchers found that age is a risk factor for more severe cases of COVID-19. And while kids weren’t immune, they were less likely to develop symptoms or get very sick. Since then, some people have come to believe that kids either couldn’t get it or pass it on to others. More recently, however, a pair of studies have suggested that kids are not only ‘silent spreaders’ of COVID-19 but also a possible driving force behind the pandemic.

So, which scenario is correct? Are kids ‘super spreaders’ who are silently transmitting COVID-19? What does this research actually show?

William Raszka, MD, a pediatric infectious disease specialist at the University of Vermont Medical Center in Burlington, helps answer these questions and make sense of the ongoing deluge of information.

Weighing the evidence
As many parents send their kids back to school, many want answers. Right now, those answers are hard to find. Taking a closer look at what researchers have done could provide some clues, according to Dr. Raszka.

Consider one large July 2020 study from South Korea published in Emerging Infectious Diseases. For the study, researchers looked at 10,592 household contacts of people with confirmed cases of severe COVID-19. The results showed that households with children between the ages of 10 and 19 years old had the highest rate (18.6 percent) of infection among other household members.

Here’s the catch: The researchers went on to write that they “could not determine the direction of transmission.”

That’s important, because without knowing who infected who it’s impossible to say whether children infected other people or vice versa.

Researchers in South Korea did just that in a follow up August 2020 study published online in Archives of Disease in Childhood. The study is the largest of its kind so far and included 107 children who tested positive for COVID-19. Researchers confirmed only one instance in which COVID-19 spread from a child to another family member. The case involved a 16-year-old girl who had just returned from the UK. The girl infected her younger sister, but not her parents.

Other studies in Switzerland, China, France and Australia have also taken a closer look at the direction of transmission. Results seem to show that children are less likely to spread COVID-19 than adults.

“I would say that overall the data is consistent with adults driving this pandemic, not so much the children,” said Raszka. “Children just don’t seem to be transmitting it as much as you would have guessed, particularly young children.”

The debate continues
Recently, two large studies have reignited the debate—just in time for the new school year.

One study suggests kids are 'silent spreaders.' This research comes from South Korea. The August 2020 study published in JAMA Pediatrics included 91 children who were either in hospitals or isolation facilities after they tested positive for COVID-19. Results showed that 22 percent of children were asymptomatic during the entire study period of 16 days. That might sound like a large percentage of children from the general population are asymptomatic when they have COVID-19.

But that would be incorrect, according to Raszka. Children in this study by definition had already tested positive for COVID-19. Drawing from a larger pool of children with and without COVID-19 shows different results. For example, one large August 2020 study published in JAMA Pediatrics involving 33,041 children who were seen by doctors in San Francisco for various medical reasons—not just for COVID-19—showed that just 0.65 percent of them were asymptomatic for COVID-19.

In the South Korea study, researchers also used a polymerase chain reaction (PCR) test to look at how levels of RNA—the genetic material that makes up the COVID-19 virus—change throughout the course of infection. They found that viral RNA was detectable in the noses of asymptomatic children for an average of 14.1 days.

But a closer look, shows that the PCR data came from only 29 children, not the entire study. And researchers did multiple rounds of PCR, allowing them to detect minute amounts of RNA.

“They were detecting the tiniest fragments of material. Down at that end, those people are by definition not infectious,” Raszka explains.

Another study suggests kids are 'super spreaders.' The second study that made recent headlines comes from researchers at Harvard University. The August 2020 study published in The Journal of Pediatrics included 192 children who either had symptoms or had a known exposure to COVID-19. Eleven children were asymptomatic at the time of testing, and just three of these children tested positive for COVID-19.

Researchers used PCR to look at viral load in nasal swabs. They found that the viral load in pre-symptomatic children in the first few days of infection was higher than adults who were on ventilators for severe COVID-19 in intensive care units.

Be careful when jumping to conclusions about these results, Raszka advises. It’s impossible to draw conclusions without knowing how high viral loads were in these very ill adults during their first few days of infection, when they could have been walking around and infecting other people.

“Almost everyone agrees that the amount of viral material detected in the nose is highest at the onset of illness. The viral load drops over time,” Raszka says. “Comparing children within two days of symptom onset with adults who may have been as many as 26 days after symptoms started is an inappropriate comparison.”

At the end of the day, Raszka says these two more recent studies don’t add much to the debate. Even the authors acknowledge that they could not determine which way transmission went, from adult to child or the other way around.

There’s been a lot of hype about these two studies,” Raszka says. “When I look at them, what they say to me is that children, just like adults, have virus in their noses at the onset of their illness. That’s it.”

What viral load is and why it matters
Importantly, what these studies can’t tell us is whether a child with detectable amounts of viral genetic material in their noses is still infectious.

Viral load refers to the amount of detectable virus particles in a sample of body fluid like blood or nasal secretions. Higher viral load has been associated with more severe illness. Higher viral loads may increase the likelihood of transmission, but not necessarily.  

Viral transmission also has to do with infectivity, whether or not a virus is still active and can establish infection.

“The PCR data can’t say anything about infectivity,” Raszka says. “The CDC guidelines say that people are not considered infectious 10 days after symptom onset if their symptoms have improved and they do not have a fever.”

In cases where children have passed on SARS-CoV-2, the coronavirus that causes COVID-19, younger children do not seem to be as good at it as older children. Right now, no one really knows why. It could be that younger children don’t cough as hard, or they just have smaller lungs so they don’t breath out as much air, Raszka adds.

Should kids really be in school?
The decision to send your children back to school is an individual one that also depends on your personal risk factors for COVID-19, community transmission in your area and the safety measures and protocols your school has implemented to curb the spread of the disease.

That said, kids do benefit from being in the classroom, particularly those who rely on critical school programs, according to Raszka.

“Children need to be in school,” he says. ”School is important for their emotional, academic and physical development, and to address inequalities across society. If children are not in school, many will be left behind.”  

To open schools safely, appropriate protection measures need to be in place, especially in areas where COVID-19 transmission is high. Masks need to be worn, schools need to be outfitted appropriately for social distancing and children with symptoms need to stay home, Raszka says.  

Lessons learned from a sleepaway camp in Georgia provide an example of what not to do. There, not everyone wore masks. Staff did not open windows and doors to increase ventilation, and children sang and cheered vigorously indoors. Among 344 camp attendees with test results, 76 percent eventually tested positive for COVID-19. 

Perhaps the number one thing is to knock down community transmission of COVID-19. That means wearing a mask, unless there’s a medical or developmental reason not to, according to Raszka.

“We have to do things to prevent spread of the disease,” he says. “Society will have to decide what’s more important: to open schools or open bars. I’m willing to give up having a glass of wine so that children can enter school. I’m willing to wear a mask so that children can go to school.”

Medically reviewed in September 2020.

Sources:
Centers for Disease Control and Prevention. “Preparing K-12 School Administrators for a Safe Return to School in Fall 2020.” August 2020.
Park YJ, Choe YJ, Park O, et al. “Contact tracing during coronavirus disease outbreak, South Korea, 2020.” Emerging Infectious Diseases. October 2020.
Kim J, Choe YJ, Lee J, et al. “Role of children in household transmission of COVID-19.” Archives of Disease in Childhood. Published Online First. August 7, 2020.
Danis K, Epaulard O, Bénet T, et al. “Cluster of Coronavirus Disease 2019 (COVID-19) in the French Alps, February 2020.” Clinical Infectious Diseases. 2020;71(15):825-832.
Han MS, Choi EH, Chang SH, et al. “Clinical Characteristics and Viral RNA Detection in Children With Coronavirus Disease 2019 in the Republic of Korea.” JAMA Pediatrics. Published online August 28, 2020.
Sola AM, David AP, Rosbe KW, Baba A, Ramirez-Avila L, Chan DK. “Prevalence of SARS-CoV-2 Infection in Children Without Symptoms of Coronavirus Disease 2019.” JAMA Pediatrics. Published online August 25, 2020.
Lael M. Yonker, MD, Anne M. Neilan, MD, Yannic Bartsch, PhD, et al. “Pediatric SARS-CoV-2: Clinical Presentation, Infectivity, and Immune Responses.” The Journal of Pediatrics. August 19, 2020.
Zheng Shufa, Fan Jian, Yu Fei, Feng Baihuan, Lou Bin, Zou Qianda et al. “Viral load dynamics and disease severity in patients infected with SARS-CoV-2 in Zhejiang province, China, January-March 2020: retrospective cohort study.” BMJ. 2020.
Centers for Disease Control and Prevention. “Duration of Isolation and Precautions for Adults with COVID-19.” September 2020.
Centers for Disease Control and Prevention. “SARS-CoV-2 Transmission and Infection Among Attendees of an Overnight Camp — Georgia, June 2020.” August 7, 2020.

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