Children between the ages of 10 and 19 are more likely to spread the coronavirus within a household than younger children or adults, according to a new epidemiological study from South Korea. The findings, released on the US Centers for Disease Control and Prevention website, come as countries across the world grapple with the heated question of how and when to reopen schools amid fears of a resurgence in cases when students return to the classroom. The researchers traced and tested more than 59,000 people who had contact with 5,706 South Korean Covid-19 patients between January 20 and March 27 and found that, on average, 11.8 percent of household contacts tested positive for the virus. For people who lived with infected older children, 18.6 percent tested positive for the virus within about 10 days after the initial case was detected — the highest rate of transmission among the age groups studied. Children under the age of 10 spread the virus at the lowest rate, though researchers warned that the figure may have been impacted by school closures and could change when they reopen.