anyplace that's full of germs or sick people. Typically involves you catching a cold or a bug of some kind after some inconsiderate jerk coughs on you or something of that nature.
When a door-to-door pest control salesman acts like your best friend to sell you shit you don't need to the extent that they become a pest themselves: they're a pestie.
Oh look, I've got another segway-riding pestie at the door.