Kids under 5 may carry a higher viral load of coronavirus. Here’s why experts say they’re less likely to spread it

Korin Miller
·6 mins read

For months, experts have stressed that younger children are less likely to transmit COVID-19 and usually do not experience serious cases of the virus. But a new small study is calling some of that into question.

The study, which was published in JAMA Pediatrics, analyzed the results of nasopharyngeal swabs collected in March and April on 145 COVID-19 patients with mild to moderate illness. The swabs were taken within a week of the patients — who ranged one month to 65 years old — experiencing symptoms.

The researchers discovered that children younger than age 5 hosted up to 100 times as much of SARS-CoV-2, the virus that causes COVID-19, in their upper respiratory tract as adults. There were no differences in the viral loads (i.e. the amount of the virus in an infected person’s body) between children aged five to 17 and adults.

The results indicated that “young children have equivalent or more viral nucleic acid in their upper respiratory tract compared with older children and adults,” the researchers wrote.

It’s important to note that the study is small, but it does seem to challenge what we already know about COVID-19 in children. “We are always learning more about COVID-19 and we may start changing the way we think about how this virus is being transmitted,” Dr. William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Yahoo Life. “This has COVID-19 looking very much like influenza,. With influenza, children are the great disseminators because they produce more virus and shed the virus for a longer period of time than do adults.”

Still, experts stress that parents and others should be cautious about how they interpret this data. “This is another piece in the puzzle of how young children are affected by this new coronavirus,” Dr. Christopher Carroll, a pediatric critical care physician at Connecticut Children's who has been researching COVID-19 in children, tells Yahoo Life. “Children seem to be relatively spared from severe illness, but we have much to learn about how young children spread coronavirus to each other and to adults.”

“I don’t think there’s enough information in the study to be able to exactly extrapolate what someone should do,” Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Life. “We’ve always known children can get COVID-19, but the question is how does that translate into a transmission risk?”

Adalja stresses that a high viral load doesn’t necessarily mean that young children are more likely to spread COVID-19. “No one ever said that children don’t have the virus in their nose and at levels that are comparable to older adults who do transmit it,” he says. “You still have to take that information and translate it.” He cites previous epidemiological research that suggests children don’t efficiently spread the virus.

A study of nearly 65,000 people in South Korea published by the Centers for Disease Control and Prevention (CDC) in July found that children younger than age 10 are less likely than adults to spread COVID-19 to other people. The study also found that children between the ages of 10 and 19 can spread the virus as efficiently as adults. That particular study has been cited by some as evidence that younger children, at least, should resume in-person schooling.

Other research has also suggested that children aren’t efficient spreaders of the virus. An epidemiological study from New South Wales, Australia, analyzed data from 15 schools with confirmed cases of COVID-19 and found a total of 18 people — nine students and nine staff members — contracted the virus. Those people had the opportunity to spread the virus to up to 735 students and 128 staff who were in close contact with them, but no teacher or staff member contracted the virus from those initial cases. Instead, just one elementary school student and one high schooler may have contracted the virus from one of the initial cases.

Another study, this one from France’s Institut Pasteur, analyzed data from 1,340 people in a town outside of Paris and found three probable cases of COVID-19 among children that didn’t lead to more infections in other students or teachers.

But Schaffner points out this data comes from areas where the spread of COVID-19 is more controlled than it is in the U.S., making it hard to translate for families in America.

As for why children don’t seem to be efficient spreaders of the virus — in other countries, at least — that’s up for debate. “Younger children may be less likely to be symptomatic and there may be less opportunity for the virus to disseminate because they’re not coughing or sneezing,” Adalja says. Younger children are also shorter and their respiratory droplets fall to the ground faster than those of adults — giving them less of an opportunity to infect others, he says. But, Adalja stresses, these are all just theories at this point. “There are still a lot of questions around this,” he says. “It doesn’t seem to be that they don’t have the virus— they’re just not transmitting it as much.”

As for what this new study says about in-person schooling resuming, Carroll says this latest data “provides more information, but doesn’t tell us much about how re-openings will go.” While Carroll says people can’t “draw any conclusions about whether children younger than five years are more likely to infect adults” based on this study, Schaffner says it’s not a bad idea for families with young children to take extra precautions when it comes to interacting with vulnerable family members. “Maybe have young children keep their distance, only hug vulnerable family members around the waist, and avoid direct kisses on the face,” he says. “It also can’t hurt to wear those masks around the grandparents.”

For the latest coronavirus news and updates, follow along at https://news.yahoo.com/coronavirus. According to experts, people over 60 and those who are immunocompromised continue to be the most at risk. If you have questions, please reference the CDC’s and WHO’s resource guides.

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