One of my ball pythons likes to give kisses, and he also likes to crawl all around your face and I have never been sick from one. But then again I have also had to sleep in palm groves in Iraq getting pooped on by pigeons during the bird flu scare and never got sick from that either.
I am not even that careful about washing my hands after touching my snakes (after cleaning the cages I am though) I guess I just have a real good immune system.