Japan should prepare for the possible arrival of a “twindemic” — a mixture of influenza and COVID-19 infections — experts say, after an unusually early flu outbreak at a school in Tokyo this week.

A public elementary school in Tachikawa, western Tokyo, canceled both of its third grade classes on Tuesday and Wednesday after 14 of the 45 students tested positive for influenza, according to the Tokyo Metropolitan Government.

This was the first cancellation of a school class due to a flu outbreak in the 2021-2022 season, which started last September. School closures or class cancellations due to flu viruses are common in the winter but rare in the summer.