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Children with COVID-19 carry as much or more coronavirus in their nose as adults, suggesting that they could pose a serious infection risk if schools and day care centers reopen, a new study argues.
Coronavirus testing performed in Chicago in March and April shows that children and teens tend to have as much virus in their nasal passages as adults, according to a research letter published online July 30 in JAMA Pediatrics.
In fact, children younger than 5 carried the highest viral loads, the researchers reported.
"It's concerning the youngest individuals were the ones with the highest amount of virus," said lead researcher Dr. Taylor Heald-Sargent, a pediatric infectious diseases specialist at Lurie Children's Hospital in Chicago. "They are not always the ones who are washing their hands or wearing their masks."
The findings call into question earlier epidemiological studies seemingly showing that children do not tend to spread the novel coronavirus between themselves or regularly infect adults.
Based on those studies, the U.S. Centers for Disease Control and Prevention argued last week for the reopening of the nation's schools.
"Some of the arguments that have been made in regard to schools and day cares opening is that perhaps children are unable to make the virus as efficiently in their nose, and that's why they're not as sick," Heald-Sargent said. "This data would argue against that. They are able to sustain replication, the same amount as older individuals, if not more."
For this study, Heald-Sargent and her colleagues took a look back at nasal samples taken from 145 patients diagnosed with COVID-19.
The researchers found that young children had average viral loads 10 to 100 times greater than adults.
"Kids certainly have virus and are replicating virus in their nose as efficiently, if not more efficiently, than adults," Heald-Sargent said. "It would be logical they can also spread the virus or transmit the virus."
However, that infection risk simply hasn't been demonstrated in real-world epidemiological studies, counters Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, in Baltimore.
"It's one thing to find virus in the nasal passages of a child versus finding epidemiological evidence of children passing it on to other people," Adalja said. "That's the key thing -- we're still not seeing outbreaks being driven by children to the extent they are driven by older individuals, and that's despite the fact that they have the virus in their nose."
According to the CDC, just 7% of U.S. COVID-19 cases, and less than 0.1% of related deaths, have occurred in people under the age of 18. And so far in 2020, fewer children have died from COVID-19 than typically die from the flu in a given year.
It remains a mystery why kids haven't been shown to be as infectious as adults when it comes to COVID-19, Adalja said.
It could be that children don't get as sick and therefore don't cough as much, spreading airborne virus, Adalja said. It also could be that because children are smaller, their airborne respiratory particles are more likely to fall to the ground before an adult can inhale them.
Heald-Sargent thinks the problem might be with the timing of the epidemiologic studies that showed low transmission rates in children.
"A lot of the epidemiologic surveys have been done in a period of social distancing and isolation, where schools were shut down quite early and day cares as well," Heald-Sargent said. "The people who were going out in the community were the adults. They were the ones at work and going to the store."
As lockdown restrictions have relaxed, more spread is being observed among children, Heald-Sargent said.
For example, a study from South Korea earlier this month found that kids 10 or older can spread the virus just as efficiently as adults.
"I'm not saying schools shouldn't reopen or day cares shouldn't reopen. It's a very nuanced and complicated discussion, and different for different areas," Heald-Sargent said. "We can't assume that children cannot spread the virus. Everyone is assuming because it hasn't been seen, it does not happen. Now I think we need to challenge that assumption."
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