Syag, you are right. and mazal tov. I am not sure what is the point discussing the person who went mishugene and about whose existence we know second-hand. At the same time, we have here a sensible person admitting to his behavior …
there is also a difference between you meeting one person with strep who is also not expecting to meet someone who is vulnerable and a pandemic situation where everyone is surrounded by potential dangers. Just put yourself in the shoes of someone who might be vulnerable, and then he needs to go to the store, and people around do not do a simple thing, required by law (NY store mandate was lifted Feb 2022).
To use your analogy, say, I know I had exposure to strep and I see a little baby in the library. I am going to avoid that baby or where a mask if I need to pass by.