There has been a meme going around since October that masks caused a secondary bacterial infection (pneumonia) that actually caused the majority of the deaths in the 1918 Spanish Flu pandemic. I just saw this for the first time on Sunday.
This meme is not true.
It is true that most of the deaths were caused by bacterial pneumonia. It is not true that wearing masks is what caused the bacterial infection. What caused the bacterial pneumonia is that the influenza infection destroyed cells in the esophagus and lungs that would normally keep bacteria from penetrating farther down. With the defenses weakened, the bacteria had a way into the lungs.
See here and here and here and here for more.
I originally posted this on Facebook on Monday.