Bacteria can't live when it's cold? Fuck off, author, you don't know shit. If that was the case then it wouldn't be possible to get sick during winter. Actually, more than that, live wouldn't exist in those places. The human body is full of bacteria(millions of them, or something like that). There are bacteria everywhere, the air included. It's just that most aren't bad for humans. On the contrary, life kind of depends on bacteria for lots of things.