Kids with asymptomatic coronavirus infections may have active virus in their bodies for weeks, scientists say

Children infected with Covid-19 can shed the virus for weeks, even after their symptoms clear or if they never develop symptoms, according to a new study published Friday in the medical journal JAMA Pediatrics.

Researchers observed 91 kids with Covid-19 from Feb. 18 to March 31 across 22 hospitals in South Korea, one of the earliest countries hit by the coronavirus pandemic.

About 22% of the children, who were under the age of 19, were asymptomatic, meaning they never developed symptoms. The remaining children had symptoms that were detected before or shortly after their diagnosis. Duration of symptoms varied, with some children presenting symptoms for as little as three days, while others had symptoms for nearly three weeks, according to the study.

Overall, researchers said the virus was detectable for an average of about 2½ weeks in children’s respiratory tracts.

The researchers found nearly half of the children who were symptomatic and a fifth of the asymptomatic children were still shedding after being tested at three weeks. They said the duration the asymptomatic children were shedding could have been even longer, since the true date of their infection is unknown.

“This is striking data,” Drs. Roberta DeBiasi and Meghan Delane of Children’s National Hospital and Research Institute wrote in an editorial published alongside the study. They were not involved in the research. 

“These findings are highly relevant to the development of public health strategies to mitigate and contain spread within communities, particularly as affected communities begin their recovery phases,” they said, adding the role of children in spreading the disease still needs to be further examined.

It remains unclear if the children were infectious while shedding and, if they were, for how long. The Centers for Disease Control and Prevention has found recovered Covid-19 patients can shed the virus for up to three months after contracting it, “albeit at concentrations considerably lower than during illness, in ranges where replication-competent virus has not been reliably recovered and infectiousness is unlikely.”

The study’s authors noted that their research was limited. They were unable to analyze how infectious the children may have been due to South Korea’s strict quarantine measures. Under South Korea rules, patients with Covid-19 must stay in the hospital until they clear their infections.

STAT News reported on a study in March that found people mildly sick may not be infectious after 10 days from when symptoms start. 

The study Friday comes as public health officials and infectious disease experts say it remains unclear the role children play in spreading the coronavirus. It also comes as schools in the U.S. and other parts of the world consider whether it’s safe to reopen as the virus continues to rapidly spread.

Early in the outbreak, researchers said the virus appeared to be sparing children while being particularly severe in the elderly and those with underlying health conditions.

However, they later found the apparent lack of children among confirmed coronavirus cases could also be because kids are getting infected but developing more mild symptoms that aren’t being reported.

A study published in April in JAMA Pediatrics found many kids infected with the coronavirus develop only mild symptoms and typically recover within two weeks. The researchers analyzed 1,065 Covid-19 patients, mostly in China, under age 19.

Another report from the Centers for Disease Control and Prevention found that the majority of pediatric patients in the U.S. developed only mild symptoms such as fever or cough.

While many children may only get mild or moderately sick from the virus, some children are still at risk of severe or even life-threatening disease.

For example, some children develop Multisystem Inflammatory Syndrome in Children, or MIS-C, a rare inflammatory condition that’s similar to Kawasaki syndrome. While health officials are still learning what connection Covid-19 has with the condition, kids can experience severe complications such as cardiac dysfunction, shock and injury to the kidneys, according to the CDC.