Ugh, people are so helpful around here.
The only way to get infected is to come in contact with a vampire (via fighting). If you aren't yet a vampire, but you think you have the disease (check under you 'constant effect' spells), then go to a church and get healed. I think Cure Disease should do the trick.
If you have the Vampire Disease (Poryphoric Hemophilia), you need to either use a 'Cure Disease' potion or pray at a chapel altar. If you don't, after 3 days you will become a full fledged stage 1 vampire, and will have to do the 'Cure for Vampirism' quest from the Duke of Skingrad, I think it is. Or use the pool in Deepscorn Hollow, if you have it.