The findings have implications as day care centers and schools reopen across the country — and as a growing number of children are being diagnosed with the coronavirus.
The new report details COVID-19 outbreaks at three child care facilities in Utah from April to July.
Twelve children became infected from someone else at day care, but most had mild to no symptoms. Through detailed contact tracing, investigators were able to determine that those children then spread the virus to at least 1 in 4 people they were in close contact with outside of the child care facility. Those contacts usually included mothers and siblings.
In one case, an 8-month-old baby appears to have spread COVID-19 acquired at day care to both parents. In one case, a parent had to be hospitalized.
Download the TODAY app for the latest coverage on the coronavirus outbreak.
Two of the three asymptomatic children who had confirmed COVID-19 diagnoses spread the virus to others. Transmission also likely occurred from children to their teachers.
Before the outbreaks, the facilities had implemented some mitigation strategies, such as daily checks for temperatures and other symptoms. Some staff members were asked to wear masks.
But none of the children were asked to do so. This research suggests masks even among kids may be an important way to help stop outbreaks.
The CDC recommends children over age 2 should wear a mask in public settings to help reduce the potential for spread to others.
"While children may be spending time with other people as they return to daycare or school settings," the CDC says on its website, "it is important to remember the exposure to additional children and adults outside of daycare or school should be managed to decrease risk."
The report also recommended increased availability of COVID-19 testing, including "timely results and testing of contacts of patients in child care settings regardless of symptoms."
Day care facilities may also consider implementing policies to have staff members quarantine and get tested if family members are showing symptoms of the coronavirus. "Staff members at two of the facilities had a household contact with confirmed or probable COVID-19 and went to work while their household contact was symptomatic," the study authors wrote.
As of Friday afternoon, at least 514,000 kids in the United States have had COVID-19, according to data from the American Academy of Pediatrics.
This story was originally published on NBC News.