I'd always assumed that germ theory meant germs. Which could spread by contagion, or via aerosol (equivalent to miasma).
Early in the covid pandemic I was just perplexed. Thinking... have these "experts" never done housework? Never dusted stuff? How can they possibly believe that particles larger than 5 µm can't stay airborne?
I was right and they were wrong.
But that whole "wash your hands" and "no you don't need to wear a mask" error came from that.