Older Children Spread the Coronavirus Just as Much as Adults, Large Study Finds

In the heated debate over reopening schools, one burning question has been whether and how efficiently children can spread the virus to others.

A large new study from South Korea offers an answer: Children younger than 10 transmit to others much less often than adults do, but the risk is not zero. And those between the ages of 10 and 19 can spread the virus at least as well as adults do.

The findings suggest that as schools reopen, communities will see clusters of infection take root that include children of all ages, several experts cautioned.

“I fear that there has been this sense that kids just won’t get infected or don’t get infected in the same way as adults and that, therefore, they’re almost like a bubbled population,” said Michael Osterholm, an infectious diseases expert at the University of Minnesota....

“There will be transmission,” Dr. Osterholm said. “What we have to do is accept that now and include that in our plans.”

South Korean researchers identified 5,706 people who were the first to report Covid-19 symptoms in their households between Jan. 20 and March 27, when schools were closed, and then traced the 59,073 contacts of these “index cases.” They tested all of the household contacts of each patient, regardless of symptoms, but only tested symptomatic contacts outside the household.

Several studies from Europe and Asia have suggested that young children are less likely to get infected and to spread the virus. But most of those studies were small and flawed, said Dr. Ashish Jha, director of the Harvard Global Health Institute.