A simple "Cure Disease" potion will work if the vampirism hasn't kicked in yet. Otherwise find Morthal east of Fort Snowhawk and talk to Falion.
I found a savegame that wasn't too far (under 1 day) along and I went to the Shrine Of Talos in Winterrun after I dropped all my loot at my house. Funny thing, I actually did run into Falion and he didn't mention anything about it?
Anywho...Only lost one level out of the whole ordeal being with my last save if I traveled anywhere I was too far gone and by the time I got there I was at day 4 and was automatically attacked.