Vampires, aka immortals and undead

Thrilling and powerful.
It had been an interesting concept that intrigued me over the years and like the mystery behind the folklore, what prevents them from being real?
Their immortality, is one reason that makes it unrealistic. How can a human live forever, free from disease, free from aging, adapting heightened senses, strength and power? Oh yes, vampires are not human.

I had to remember, whoever thought this up, being human, one has a body and a soul. Alive with  a rhythm of energy.
All this is taken by turning a mortal being, sucking its life source, blood, from their bodies and then offering vampire blood in exchange..Again an interesting concept.
Before Bram Stoker, who really thought this one up? There has been rumours, speculation and unusual evidence turn up over the centuries.
Mortal to Immortal; Human to Vampire; Alive to ... Dead no, not quite - Undead.
Just a thought. ;-)