How did vampires come into being?

From folklore stories originating from the Slavic people centuries ago. When there was an unexplainable sickness or crop failure people would conclude that there must be a vampire about. People would dig up graves of potential vampires and look for symptoms, which included bloating, a red liquid coming from the mouth or nose, and hair and nail growth. All these symptoms are a part of the body decomposing. Gases in the body builds up causing bloating; gases from the body push out decomposing liquids that come out of the mouth and nose; hair and nails seem to grow when water from the body evaporates and the skin pulls back giving the illusion of growth. Peasants were the ones who were accused of being a vampire. It wasn't until the 19th century when vampire stories were published that the vampire became an aristocrat, like in Dracula published in 1897.