I will give you information about HIV, because of the topic of this forum. If you wish further info about HPV, check the STD forum.
The only ways HIV is spread are:
-Unprotected anal/vaginal penetrations.
-Sharing needles to inject drugs.
-Mother to child.
HIV is neutralized when exposed to air, and a similar effect is produced by saliva, as at least 12 different enzymes have been discovered in it and are able to neutralized the virus. The mouth is then, a really hostile environment for HIV.
I hope that helps.
All the best.