Even children with mild or no symptoms can spread Covid-19, according to contact tracing data from three Utah child care facilities released Friday.
Twelve children, including one eight-month-old, got Covid-19 in a child care facility and spread it to at least 12 people outside the facilities. The data shows children can carry the virus from child care settings to their homes, the researchers wrote in a report released by the Centers for Disease Control and Prevention.
Half a million US children have now been diagnosed with coronavirus, with a 16% increase between August 20 and September 3, according to the American Academy of Pediatrics and the Children's Hospital Association.
Though fewer children appear to experience severe illness from the virus than adults, one question that has loomed large, especially for those grappling with decisions about reopening schools and day cares, is exactly what role children play in the transmission of the virus. The CDC report suggests that they can and do spread coronavirus.
The researchers analyzed contact tracing data from 184 people with links to three child care facilities in Salt Lake County from this April to July.
They found at least two children who had no symptoms who not only caught the virus, but passed it to other people, including one mother who was hospitalized. One eight-month-old baby infected both parents.
The researchers say that two of the facility outbreaks began with staff members who had household contacts with the virus.
Overall, children accounted for 13 of the 31 confirmed Covid-19 case linked to the facility, and all of the children had mild or no symptoms.
"COVID-19 is less severe in children than it is in adults, but children can still play a role in transmission," the CDC's Cuc Tran and colleagues at the Salt Lake County Health Department wrote in their report.
"The infected children exposed at these three facilities had mild to no symptoms. Two of three asymptomatic children likely transmitted SARS-CoV-2 to their parents and possibly to their teachers."
Pediatricians have said children can help spread the virus.
"We know that children often show few or no symptoms of COVID-19. We also know they are not immune to this virus, and they can become very sick," Dr. Sally Goza, President, American Academy of Pediatrics, said in a previous statement.
The researchers say that contact tracing and timely Covid-19 testing for those in child care settings, including asymptomatic people, can help prevent spread of the virus. They recommend the use of face masks, especially for staff working in child care centers with children below the age of 2 who may be too young to wear masks.
"Testing exposed individuals who may not yet show symptoms of COVID-19 is crucial to contact tracing, which helps identify and support other people who are at risk of infection," said Goza.
In August, South Korean researchers reported that children, even those with no symptoms, can carry coronavirus in their noses and throats for weeks. Another study found that children younger than 5 have between 10 and 100 times more genetic material from the novel coronavirus in their noses than older children and adults.
Jen Christensen, Jacqueline Howard, Andrea Kane and Sandee LaMotte contributed to this article.