Long term effects from virus?

I heard some stuff about how a certain percentage of our human genes are there because of retrograde viral infections in the past. I know chicken pox makes you susceptible to shingles later. It interests me, because as the virus uses our genetic replication mechanism to spread copies of itself, it allows for mutations in our information set. Coevolution. Like updates to the firmware.
And I saw that the virus was found in seen of some patients, not sure about sexual transmission yet. Can you imagine if it becomes an STD? Pics or it didn't happen?
Just some random thoughts. I have a lot of free time lately...