A vampire is a creature from folklore that subsists by feeding on the vital essence (generally in the form of blood) of the living. In simple terms, they are evil mythological beings who roam in the world at night searching for people whose blood they feed upon. They typically drain their victim’s blood using their sharp fangs, killing them and turning them into vampires.
The most famous vampire is, of course, Bram Stoker’s Dracula.
Although modern science has silenced the vampire fears of the past, people who call themselves vampires do exist. They’re normal-seeming people who drink small amounts of blood in a (perhaps misguided) effort to stay healthy.
Are vampires real?
Vampire superstition thrived in the Middle Ages, especially as the plague decimated entire towns. The disease often left behind bleeding mouth lesions on its victims, which to the uneducated was a sure sign of vampirism.
It wasn’t uncommon for anyone with an unfamiliar physical or emotional illness to be labeled a vampire. Many researchers have pointed to porphyria, a blood disorder that can cause severe blisters on skin that’s exposed to sunlight, as a disease that may have been linked to the vampire legend.
Entertainment industry on vampires:-
There are many films, comics and popular literature on and about vampires. And you would be probably surprised to find out that vampires can actually exist and their existence does not contradict modern science!
In Stephenie Meyer’s “Twilight series” vampires can tolerate the sunlight, interact with humans (even fall in love with them) and drink animals’ blood to survive. Of course, they have to live in secrecy and pretend to be human beings. In “True Blood” TV series, however, a world is shown where vampires and humans live side-by-side and are aware of each other. Vampires can buy synthetic blood of different blood types that is sold in bottles and can be bought in every grocery store, bar or gas station. They cannot walk during daytime, so they usually come out at night.
Real vampires embrace their instinctual need to feed on blood or energy and use what mainstream culture sees as a negative. But real vampires can also help us understand, and perhaps even shed, some of the ideological baggage each of us carries.
The varied vampire community:-
Some houses, and indeed whole vampire communities, as in the case of New Orleans, will combine their efforts to organize charity events, like feeding (not feeding on) the homeless. However, despite their humanitarian efforts, real vampires don’t go around advertising who they are for fear of discrimination by people who simply don’t understand them.
More generally, this community shows that being different doesn’t have to force you onto the margins of society. Real vampires can and do exist in both “normal” society and their own communities, and that’s okay.
Karl Marx, a vampire hunter
It is surprising to learn that the works of Karl Marx are full of mentioning of vampires. In one of the cases Marx describes British industry as “vampire-like” which “could but live by sucking blood and children’s blood too”. Here is another quote: ““Capital is dead labor which, vampire-like, lives only by sucking living labor, and lives the more, the more labor it sucks”.
Marx described vampires’ habits, their greediness and their lounging for blood in such a detail that in many cases it crossed the boundaries of the mere metaphor. 
All this is very interesting because the best-known novel of vampiric genre, Bram Stoker’s Dracula, did not see the daylight until 1897, 14 years after Marx’s death. Surely, one can place the Marx’s metaphor in the wider context of nineteenth-century Gothic horror stories which were abundant these days, and of which Marx was a huge fan. On the other hand, one might assume that some of the vampire legends were true and Marx and his contemporaries were aware of that!
Existence of vampires as per Harris-Meyer-Kostova model:-
Let us assume that at the time of the events described in the first book of the series, “Dead Until Dark” (2001), the world’s vampire hypothetical population was around five million. The initial conditions of what is called “a Harris-Meyer-Kostova model” are the following: five million vampires, 6 159 million people, there are organized groups of vampire “drainers”.
