There is a fundamental grossness to playing the harmonica. You put your lips all over it and you can't help but have some tongue and saliva involved - it's got to get germy. I mean, I make an effort to keep it rinsed off but who knows how effective those efforts are and what is living way down inside it. And then when I'm playing it a lot, as I have been the last week, laziness sets in and I don't even bother cleaning it every time. I just pick it up and put it in my mouth and slide my wet lips all over it again.
I'm sure there are very simple logical regimens for keeping your harmonica sanitized but apparently I am just too lame.