Asymptomatic Children Carry Higher COVID-19 Viral Load Than Adults In ICUs, Study Finds

A study released Thursday shows that children may play a larger role in community spread of COVID-19 than previously understood.

The research out of Massachusetts General Hospital and MassGeneral Hospital for Children shows that infected children — even those without symptoms — can have higher levels of virus in their airways than adults hospitalized in intensive care units.

More than a quarter of the 192 children enrolled in the study tested positive for COVID-19. Published in the Journal of Pediatrics, the report says educational settings from daycare to high school should take the new information into account when determining how and whether in-person learning should proceed.

Some kids enrolled in the study went to an urgent care clinic for testing, while others were hospitalized with symptoms of COVID-19 or the related inflammatory illness impacting children, says Lael Yonker, lead author of the study and director of the hospital's Cystic Fibrosis Center.

“What surprised us the most was that children carried very high viral loads in their airway secretions,” she says, “loads that were higher than adults who are hospitalized for their severe COVID illness.”

With respiratory viruses, in general, a higher viral load means the virus is more likely to pass from one person to another because it’s transmitted through droplets, she says.

Testing for the study took place at a centralized COVID-19 screening center that encompassed people from a large geographic and socioeconomic range, she says. But it’s hard to apply these findings to the greater population because children often experience mild symptoms or are asymptomatic when they get sick, which makes it more difficult to realize who’s infected.

One of Yonker’s co-authors notes that kids are not immune to getting sick — which puts to rest President Trump’s contention that children are “almost immune.” At least 97,000 kids tested positive for COVID-19 in the U.S. during the last two weeks of July, marking a 40% surge in the country’s cumulative total of child cases.

The study also looked at multi-organ systemic infections that can occur as kids recover from COVID-19. The disease is linked to an inflammatory response that continues well after the infection clears out and damages the body, Yonker says. Kids can develop cardiac issues or end up in the ICU due to this inflammatory response, which the study finds is related to the body’s antibody response.

“The body's actively fighting, building these immune responses,’ she says. “But the body builds these antibodies in an uncontrolled manner and that seems to be harmful to these kids.”

With kids around the country headed back to school, the study finds temperature and symptom checks are unreliable ways to prevent the spread of the virus.

Only about 50% of the kids who tested positive for COVID-19 reported a fever — and 50% of the children who tested negative also reported a fever, Yonker says. The study also found typical symptoms of a cold or allergies were reported equally by kids who did and didn’t have COVID-19.

Parents who identify symptoms should test and monitor the child early on because the study shows kids’ viral loads are highest in the first two days of illness, she says. Exposure to someone with a confirmed case of COVID-19 should also prompt testing because kids can carry high viral loads without developing symptoms.

The study shows that contrary to initial reports and some popular beliefs, COVID-19 does not spare children and kids can play a significant role in spreading the disease, Yonker says.

“The policymakers, the people who were setting up the rules for how schools will safely be started need to take this into consideration,” she says. “And they need to consider enforcing mask-wearing, social distancing, taking advantage of remote learning when possible — pretty simple measures that can be done to make reentry into schools safer.”

Karyn Miller-Medzon produced and edited this interview for broadcast with Tinku Ray. Allison Hagan adapted it for the web.