Why is the belief in vampires so widespread through out the world?

So many cultures have their own spin on the same story through out the planet. In some places (Asia) they are very scary supernatural beings. In other places (South America) they are more animal like, but still quite frightening. And in other parts of the world (Europe & North America) they are not less frightening charismatic human like beings. Despite their differences, vampires seem to be drilled into our subconscious through out the planet. Is this idea based on a real demon, or does it have something to do with the way our brains are wired to find fear, or is it something more?