After preying heavily on the elderly in the spring, the coronavirus is increasingly infecting American children and teens in a trend authorities say appears fueled by school reopenings and the resumption of sports, playdates and other activities. Children of all ages now make up 10% of all U.S cases, up from 2% in April, the American Academy of Pediatrics reported Tuesday. And the CDC said Monday that the incidence of COVID-19 in school-age children began rising in early September as many youngsters returned to their classrooms.