Kids who test positive for the coronavirus but show no symptoms can be infectious for up to three weeks, according to a new study by two Washington-based scientists.
The findings could have major implications for teachers and staff at schools that have reopened for fall classes, and for daycare centers.
In the paper published Aug. 28, in JAMA Pediatrics, two Washington-based scientists, Robeta L. DeBiasi and Meghan Delaney, analyzed 91 COVID-19 cases among children at 22 hospitals in South Korea. They found that half the kids with symptoms and a fifth of those without symptoms shed the virus from three days to three weeks.
About 22% of the cases were asymptomatic and another 20% initially asymptomatic but developed symptoms later. Those amounts roughly correspond to the estimated percentage of COVID-19-positive adults who are asymptomatic or presymptomatic (40%). A total of 58% of the South Korean children exhibited symptoms at the time of their first test.
Previously scientists thought children who contracted COVID-19 mostly experienced mild symptoms that quickly disappear.
Another study, published in the Journal of Pediatrics on Aug. 19, examined the respiratory secretions of 192 children, adolescents and young adults who came to the hospital with symptoms of COVID-19 or suspected exposure to the disease.
Harvard Medical School researchers based at at Massachusetts General Hospital and Mass General Hospital for Children showed that the children and young adults had higher levels of the virus, or viral load, than adults fighting COVID-19 in intensive care units.
“I was not expecting the viral load to be so high,” said Lael Yonker, Harvard Medical School assistant professor of pediatrics at Mass General. “You think of a hospital, and of all of the precautions taken to treat severely ill adults, but the viral loads of these hospitalized patients are significantly lower than a ‘healthy child’ who is walking around with a high SARS-CoV-2 viral load.”
In addition, the scientists found the younger children had far lower levels of ACE-2 receptors, the protein that provides the entry point for the coronavirus to attach itself and infect a wide range of human cells, than older children and adults. That contradicted previous assumptions that kids are less likely to become infected or seriously ill because they possess fewer ACE-2 proteins.
The study’s authors concluded that children may be a potential source of contagion in the SARS-CoV-2 pandemic in spite of milder disease or lack of symptoms.
While children with COVID-19 are not likely to become as seriously ill as adults, they can spread infection and bring the virus into their homes if they attend school as asymptomatic carriers or carriers with few symptoms, the scientists wrote.
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Mike Moffitt is an SFGATE Reporter. Email: firstname.lastname@example.org. Twitter: @Mike_at_SFGate