useing rubbing alcohol might be your best bet friend,it kill germs and a lot more plus it dry's fast and shouldn't hurt anything,but,I'd hang about and ask the pro's.I'd hate it if you used alcohol and it mess something up.I use it on a swab to clean electronics that can't gain wet..
mix a small batch of 10% bleach and 90% marine...let it soak for 10 minutes.
then clean up it off with soap and dampen.
if it doesn't still taste like bleach progress blow ur heart out on the thing.
NEVER soak your harmonica within water or soap. It will definitely ruin it. Pour a bit of rubbing alcohol within a tupperware bowl and quickly dunk it and move it around vigorously for a few second. Pull it out and shake as much of the excess alcohol off of it as you can.
Also, you could do your immune system a favor and give it a haphazard to do what it's supposed to do, so that someday you don't find yourself incapable of fighting off the weakest of germs.
Answers: I'm not sure, except make sure you don't get hose on the reeds, or else it will warp and then you'll enjoy to buy a new one which you should do anyway. Perhaps some isopropyl alcohol wiped kindly around the metallic areas would do. But do NOT soak it in water.