" In a strange twist on the concept of flu prevention, ‘vaudeville theaters were only allowed to be half full – members of the audience had to leave the seat on either side empty so that they would not breathe on one another. To further protect themselves many wore surgical masks, so that even when they laughed the sound was muffled. "

― Catharine Arnold , Pandemic 1918: The Story of the Deadliest Influenza in History