Possibly, sexually transmitted diseases (STDs) may influence sexual activity.
Herpes, for example, may heighten sexual feeling because it makes that area terribly itchy and makes you aware of it all the time.
And that makes you want to have more sex - which can only be a good thing for the virus.
All living things - including viruses and bacteria - have only two basic urges: to survive and reproduce.
An STD knows that to survive it has to be passed from host to host, and that means doing all it can to make you want to have sex.