A new study published by researchers in South Korea found that children can carry coronavirus in their noses and throats for weeks without showing any symptoms.

The study, published in the journal JAMA Pediatrics on Friday, included data on 91 asymptomatic, presymptomatic and symptomatic children diagnosed with coronavirus between Feb. 18 and March 31 at 22 health centers throughout South Korea.

Among those 91 children, 22% remained asymptomatic throughout the study, 20% were presymptomatic, meaning they developed symptoms later on, and 78% did show symptoms that included fever, cough, diarrhea, abdominal pain and loss of smell or taste.

“In this case series study, inapparent infections in children may have been associated with silent COVID-19 transmission in the community,” researchers wrote.

Recently, the Atlanta-based Centers for Disease Control, updated its guidelines on asymptomatic testing, stating that some people without symptoms may not need to be tested, even if they’ve been in close contact with someone known to have the virus.

The study found that traces from the virus were detectable in the children for a mean of 17.6 days overall, according to CNN. Even in the children who had no symptoms, the virus was detectable for an average of 14 days.

“A surveillance strategy that tests only symptomatic children will fail to identify children who are silently shedding virus while moving about their community and schools,” they wrote. “In regions where use of face masks is not widely accepted or used by the general public, asymptomatic carriers may serve as an important reservoir that may facilitate silent spread through a community.”