theslitherydeee: That's where medieval vampires are thought to come from as well. They bury someone alive, the poor sap manages to get out, and then are promptly killed for being vampires.
The most valid explanation is the theory that the tales about vampirism originated from rabies epidemics. After an infection the rabies virus moves quickly along the axons until it reaches the brain, where it causes some drastic changes in the shown behaviour, most of them consistent with vampiric traits.
Sensory hypersensitivity - rabies victims usually are very sensitive to sensory input. They react with flight behaviour to loud noises, strong light and intensive smells (garlic, anyone?). And for some strange reason rabies victims suffer from hydrophobia (fear of water), even the sound of running water can lead to generalized seizures.
Restless and aggressive behaviour - is often shown by rabies victims. They become nocturnal, often very aggressive and they suffer from, well, I could not find the english translation for this... the german word is "Beisszwang", which literally means "being forced to bite". Rabies victims feel compelled to bite other animals/people in order to spread the virus.
Increased salivation - the saliva can not be swallowed, because swallowing causes cramps in the throat, so the saliva just leaks out of the mouth.
It is also noticeable that Hungary suffered from a widespread rabies epidemia between 1721 and 1728, which is roughly consistent with time and place of the origin of the vampire myth.
