Sadly there is a percentage of travellers who this will simply not work on. I met a backpacker last year who was telling me that he refused to wear masks in Mexico City (even on the metro) because he didn't believe in any of this fear. He even said (in a bragging sort of way) that he had been drinking tons of tap water, and he's fine.

I tried to make the case that maybe he should do it for the elderly Mexicans who is he making uncomfortable by not wearing a mask, even if he personally doesn't care. Do you know this piece of shit actually said? "I think that by showing my face I'm showing them that everything is alright, and they will feel better"