Some of the schools around me closed for a day in late January 2020 to clean due to an influenza outbreak. I thought it was strange at the time since there was

Some of the schools around me closed for a day in late January 2020 to clean due to an influenza outbreak. I thought it was strange at the time since there was no evident increase in illness among adults I know. I figure it was a bad strain that had been lying dormant for a while, so kids had no immunity to it. It was very specifically stated at the time to be influenza, as opposed to just higher-than-normal absences due to non-specific diseases. I think the absence rate was something like 30%.