Vampire Biology

Before speculating on any specific pathogens capable of producing a condition akin to vampirism, I wish to write about an old line of reasoning on how vampires manage to survive on a diet which contains so much water and so little else. Speculation on the subject of the dietary requirements of vampires must first deal with what the blood is actually being used for. Some fiction, including Elrod's novels, seems to assume that it is …

…of rebuilding its human host to do one of two things. It must either produce more energy from limited materials than living organisms can manage by chemical means (the cold fusion suggestion) or it must conserve energy so dramatically -- without compromising the strength and speed associated with the condition -- that the scant energy available from blood will suffice. These problems invite speculation that something other than a living vampiric disease/parasite is involved.