Adolescents who contract Covid-19 usually do not get as sick as adults and often experience few if any symptoms, but they can spread the novel coronavirus that causes the disease to others.
Scientists from the Centers for Disease Control and Prevention and the health departments of four states — Georgia, Illinois, Massachusetts and Rhode Island — described a 13-year-old girl who became infected with the coronavirus just before a three-week family gathering. Eleven other relatives, including her mother, her father, two brothers and two grandparents, also became infected.
“This outbreak highlights several important issues,” wrote the authors, led by Dr. Noah G. Schwartz of the C.D.C., in the article, which was published on Monday. “First, children and adolescents can serve as the source for Covid-19 outbreaks within families, even when their symptoms are mild.”
The finding, which appeared in the C.D.C.’s Morbidity and Mortality Weekly Report, may also fit with claims that teenagers are more likely become infected and spread the virus than younger children.
“This doesn’t necessarily mean that all 13-year-olds can cause outbreaks like this,” said William Hanage, a professor of epidemiology at the Harvard T.H. Chan School of Public Health who was not involved with the research. “But it does mean that some 13-year-olds can.”
The potential for children to transmit the disease is “now pretty much established,” Dr. Hanage said.
In the new case report, the girl was exposed to the coronavirus away from home in June, the authors reported. However, four days after the exposure, a rapid antigen test reported a negative result. Antigen tests for the coronavirus, however, often produce erroneous results. Two days later, she experienced nasal congestion, her only Covid-19 symptom.
The same day, she, her parents and two brothers traveled to a get-together of 20 relatives over the next three and a half weeks. Fourteen of them stayed in the five-bedroom, two-bathroom house at varying lengths of time ranging from 8 to 25 days; they did not wear face masks or stay at least six feet apart from each other. Six other relatives came by during two days — once for 10 hours, the other time for three hours — but maintained physical distance and remained outdoors, although they too did not wear face masks.
Of the 14 staying at the house, 12 of them, including the girl, came down with Covid-19, with the onset of symptoms appearing up to 18 days after the start of the gathering. Their ages ranged from 9 to 72. Not all of them were likely to have been directly infected by the girl; the virus may have been spread by several people in the house.
One was hospitalized, and another went to an emergency room because of trouble breathing. Both recovered. No additional cases have been linked to the family gathering.
Two of the girls’ cousins, 14 and 16 years old, did not contract the coronavirus. None of the day visitors who stayed outside the house became ill.
“It re-emphasizes the importance of basic public health precautions, even with people we know and love,” said Dr. Megan L. Ranney, a professor of emergency medicine at Brown who was not involved with the study.
Those include avoiding spaces indoors where people are close together. “Staying outside is always safer, as shown by transmission rates within this study,” Dr. Ranney said.
It also illustrated that other recommendations of public health officials have merit: that physical distancing helps prevent spread of the coronavirus, that rapid antigen tests should be confirmed by more reliable polymerase chain reaction tests and that someone exposed to the coronavirus should remain isolated from others for 14 days.
“Physical distancing, face mask use, and hand hygiene reduce transmission; gatherings should be avoided when physical distancing and face mask use are not possible,” the authors wrote.