SARAH MCCAMMON, HOST:
A new study shows that people under 20 are less likely to get infected with the coronavirus. And when they do, they're less likely to get sick. The report could explain lower rates of transmission in some countries with younger populations and could have implications for how schools reopen in the fall. NPR's Jason Beaubien has that story.
JASON BEAUBIEN, BYLINE: Why the new coronavirus appears to be affecting children differently than adults has been one of the great mysteries of this pandemic. And it's a question that Rosalind Eggo from the London School of Hygiene & Tropical Medicine and her colleagues set out to try to answer.
ROSALIND EGGO: What we found was that people under 20 were about half as susceptible to infection as people over 20.
BEAUBIEN: So kids and teens appear to be far less likely than adults to actually get infected with the virus. And when children do get infected, they're far more likely than adults to have only mild symptoms or no symptoms at all.
EGGO: Yeah, we found quite a big difference in how likely people were to show clinical symptoms with age.
BEAUBIEN: Overall, only 20% of young people infected with the virus showed symptoms while more than 70% of elderly were symptomatic. Eggo's research, which just got published in the journal Nature, uses mathematical modeling to examine coronavirus data from six countries - China, South Korea, Italy, Japan, Singapore and Canada. The results are similar from a study done by the CDC that found that while kids under the age of 18 make up 22% of the U.S. population, they accounted for less than 2% of reported cases.
The implications of how this virus is playing out in children are huge. For example, are countries with younger populations at less risk of a large outbreak? Can schools reopen safely? Should kids be allowed to visit their grandparents, or is it the middle-aged people who should be kept away from the elderly? Dr. Megan Culler Freeman, a virologist and pediatrician at the University of Pittsburgh School of Medicine, says kids are typically major spreaders of respiratory diseases.
MEGAN CULLER FREEMAN: So the kids are going to day care. They're going to school. Especially the younger ones aren't necessarily as polite with their coughs and sneezes, so it's really easy for those diseases to spread.
BEAUBIEN: And yet, that's not what we've been seeing so far with COVID-19. Freeman studied coronaviruses for her Ph.D. She says kids are clearly susceptible to the other known coronaviruses that circulate each year during the cold and flu season, yet something different is happening with this new one.
CULLER FREEMAN: We've had a tremendous number of case numbers throughout both the United States and the world. And really, a minority of those have been identified in children. So you'll see somewhere between 2% and 5% of all of the infections will be in children under the age of 18, which is kind of amazing.
BEAUBIEN: There are a couple of hypotheses for why this is. One is that kids get a milder form of the disease. If they aren't showing symptoms, they may never get tested, and thus those infections aren't counted. Freeman says there's also some research that shows that the receptors in human cells that the coronavirus latches onto are less developed in younger people. But both the researchers who just published their work in Nature and Freeman say it's still unclear exactly why so few cases have been detected in kids and whether that trend will continue.
EGGO: It does seem that kids are less affected than adults. But I think their role in community spread is still somewhat untested, and part of that is because we did shut down the schools. So we don't know what - how things are going to change if that variable is back in play.
BEAUBIEN: Some countries around the world have started to reopen schools, but that's mainly been in places like Hong Kong and New Zealand, where transmission levels are incredibly low. If schools reopen in the U.S. while transmission levels remain high, we may get a clearer picture of just how much transmission is being driven by children.
Jason Beaubien, NPR News Transcript provided by NPR, Copyright NPR.
