There were a few steps in between. Miasma theory said bad air/smells caused disease, which tried to explain infections spreading person to person. You might wear a satchel of basically potpourri to protect from plague if you believed this one.
Another was the “body humors”, where disease was thought to be caused by imbalances of four basic fluid types in the body. If you believed this one, you might try to treat someone by draining a whole bunch of their blood. Y’know, while they’re already sick.
There were a few steps in between. Miasma theory said bad air/smells caused disease, which tried to explain infections spreading person to person. You might wear a satchel of basically potpourri to protect from plague if you believed this one.
Another was the “body humors”, where disease was thought to be caused by imbalances of four basic fluid types in the body. If you believed this one, you might try to treat someone by draining a whole bunch of their blood. Y’know, while they’re already sick.