Lore:Book of Bloodfiends, Ch. 3—Water

If one of your friends or family dies, you don't want them coming back as a bloodfiend! We found that pouring blessed water over all exposed areas of the corpse effectively prevented the spread of the plague.

Sadly, this method is less effective with the living, as the blessed water will simply run off your skin as you move around. I suppose this means it would be worth trying on an immobile person, but we were not able to test this theory.