You might want to think of it like this.
Human mouth is filled with bacteria > Butt of cigarette goes into mouth of stranger > Stranger throws cigarette on the ground which also has bacteria > You pick it up with your bare skin > You do something with your hands like touch your face, etc.
I’m normally not a stickler for bacteria because I think it’s healthy to build up your immune system, but the Coronavirus is in my city so all I see is people in masks at the moment.
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