Children younger than five years are susceptible to coronavirus infection but generally present with mild symptoms compared with older children and adults. Whether they spread the virus as older children and adults is still not clearly known.

Abandon the notion that children, unlike adults, are not susceptible to novel coronavirus infection and show symptoms of mild to moderate disease. Compared with adults, young children generally present with only mild symptoms and may not need admission to a hospital but they do get infected. But whether they dive coronavirus spread is still being debated.

In a study published in JAMA Pediatrics, researchers found that children younger than five years harbour more viral RNA in the upper respiratory tract than adults and even older children. The amount of coronavirus RNA could be 10- to 100-fold more in younger children than adults. However, the researchers only looked for viral RNA and not for live, infectious virus itself. They note that paediatric studies of novel coronavirus had earlier reported a “correlation between higher nucleic acid levels and the ability to culture infectious virus”.

The researchers studied 145 patients with mild to moderate illness within one week of symptom onset. Three age groups were compared — children younger than 5 years (n = 46), children aged 5 to 17 years (n = 51), and adults aged 18 to 65 years (n = 48).

Based on the high amount of viral RNA found in young children, the authors caution about the dangers of opening schools. “We found that children under five years with COVID-19 have a higher viral load than older children and adults, which may suggest greater transmission, as we see with respiratory syncytial virus, also known as RSV,” lead author Taylor Heald-Sargent, pediatric infectious diseases specialist at Lurie Children’s and Northwestern University Feinberg School of Medicine says in a release.

“Our study was not designed to prove that younger children spread COVID-19 as much as adults, but it is a possibility,” says Dr. Heald-Sargent. “We need to take that into account in efforts to reduce transmission as we continue to learn more about this virus.”

Despite the study not looking for live viruses and studying the ability of young children in spreading the virus, the findings raise concerns about opening schools. “The [study] has important public health implications, especially during discussions on the safety of reopening schools and daycare,” he says. Cocooning of young children together in class room settings can lead to spread of the virus amongst children, if they indeed have the ability to spread the virus.

However, a news item in Science points out that unlike high school students who may transmit the virus when they have mild disease, children younger than 11 or 12  “probably don’t transmit very well”.

But a large study in South Korea that looked at over 59,000 contacts of 5,706 index cases between January 20 and March 27 has some answers to the possibility of children transmitting the virus to others. The results of a large study published in Emerging Infectious Diseases, the authors found that unlike adults, children younger than 10 years transmit the virus much less often. But the risk is not zero. However, children aged 10-19 years showed greater ability to transmit the virus especially in households. Their transmission capacity was comparable with adults.