With many students in Japan set to return to classrooms this week after the summer break, parents and teachers are worried that COVID-19 infections may spread quickly among them at school and they will then bring the virus back home.

During the summer break, which normally runs from late July to late August, there has been a surge in clusters of infections among children during club activities and at cram schools. In Tokyo, for example, 14.3% of new cases between Aug. 10 and Aug. 16 were among those age 19 or younger, up from 8.2% between March 23 and March 29, which is typically during the spring holiday.

An education ministry survey showed a total of 2,817 children up to and including those of high school age contracted COVID-19 in July, down from a peak of 6,721 cases in January. But the ministry warned that number was set to balloon due to a sharp increase in new infections driven by the highly contagious delta variant, which is now estimated to account for more than 90% of all cases in Japan.