700 Year Old Graves and Vampires Disease?

Are Vampires only as real as we make them? It seems everyone has their own idea of what a real 'Vampire' is and what they are capable of. Is their skin extremely sensitive to sunlight, do they have superhuman strength, can they compel people into forgetting, are they afraid of garlic? In todays media we see a multitude of Vampire varieties and it seems no two are completely alike. But as the old hollywood movies convey, lets assume Vampires at least have these features: The need for human blood, hurt by sunlight, pale skin, stronger than average, afraid of garlic and crosses, finally when they feed on a human they will then turn into a Vampire. 

-Skeleton of 700 Year Old Bulgarian Vampire

According to Time Magazine's Catherine Traywick's research, over one hundred 'vampire' graves were discovered in Bulgaria dating back to around 700 years ago. It was tradition in old Bulgaria to nail and stake a person several times through the chest and limbs, stopping them from returning from the dead and killing the innocent. But why were there so many people that were believed to be Vampires? Did they show traits and try to feed from a humans blood? Obviously these Bulgarians were afraid of something terrifying, why else would they stake a human through the heart, nailing them into their coffin?

Could Vampires be the result of a disease? It seems hard to believe, and if there was such a disease you would think we'd have caught on sooner. Well as The New York Times Philip Boffey states, Vampirism could be narrowed down to a disease called Porphyria. Porphyria causes its host to be extremely sensitive to sunlight, so much that it can instantly burn the skin, cause gums to recede exposing incisors, the need for a blood product known as 'heme' (patients today would receive injections for heme, but in old times suffers could have been found drinking blood from a host to help increase their heme levels), and even an aversion to garlic (supposedly this exacerbates porphyria symptoms).

 Although these symptoms fit some of the attributes of a vampire, it's hard to believe that someone suffering from a disease like this could attack people with super human-like strength and overpower a healthy person. But maybe Vampires weren't as strong as we think today? Could it be that someone infected with such a disease as Porphyria be so stricken by their need to survive, and attack a person by surprise to take their blood? Possibly they had to resort to these dreadful measures.