Our notion of vampires was created by Bram Stoker in his 1897 novel Dracula . The novel Dracula was based on the historic Vlad the Impaler who had nothing to do with vampires at all. Pop explanations that refer to the disease congenital erythropoietic porphyria are incorrect. They explain how someone could look like the Hollywood Dracula but real vampires did not look like that. The actual vampire tradition is that vampires appear to people in their dreams.
Vampires are the recently dead.
They come to their victims while they are sleeping and sit on their stomachs and gnaw at their chests. The victims turn anemic and listless. Vampires are caught by disinterring recently buried bodies and looking for a series of specific signs that are supposed to indicate vampirism. Then, of course, the vampire is staked. In actuality, these signs are typical of the normal processes of decomposition.