The Atlantic has an article about vampires and superstition. From the article:
We now imagine vampires as blood-drinking, cloaked Counts—or possibly sparkly, sexy teenagers—but throughout history everyone from the Ancient Greeks, to the Eastern Europeans, to 19th-century Americans saw them as disease victims (and sometimes simply dead miscreants) who could prey on the living from the Great Beyond.
To keep these fiends from feasting on their villages, the surviving relatives would try to physically keep them in their graves, sort of like setting up an obstacle course for the deceased.
... Part of the reason the myth persisted, it seemed, was widespread confusion over what happens to people after they die. The pagan Slavs obviously didn’t know about decomposition, but even centuries later, people might have been misled by the fact that rigor mortis eventually gives way to flexible limbs, making a corpse seem more lifelike than dead-like. Similarly, a digestive tract’s decaying ooze might have looked like fresh blood to an unwitting villager, and burial shrouds sometimes snagged on the corpses’ teeth, making them appear to be partially eaten. (Some believe this is why in Ulysses, when Stephen sees what he believes is an apparition, he cries, “Ghoul! Chewer of Corpses!”)
Eventually, similar fears migrated to the New World. During tuberculosis epidemics, 19th-century New Englanders began to notice that the relatives of TB victims began to sicken and waste away after their loved one’s death. This was before germ theory took hold, so one popular explanation was that the deceased TB victims were rising from the dead to suck the life out of their loved ones. One Connecticut town, for example, thought the solution was to exhume the remains of the dead relative and arrange the remains in a skull-and-crossbones pattern.
The Scottish writer Emily Gerard first documented the Eastern European myths that gave rise to the vampire-burial practices in a 1885 article called “Transylvanian Superstitions:"
"These restless spirits, called Strigoi, are not malicious, but their appearance bodes no good, and may be regarded as omens of sickness or misfortune. More decidedly evil, however, is the vampire, or nosferatu, in whom every Roumenian peasant believes as firmly as he does in heaven or hell."
In 1897, Bram Stoker’s Dracula, which was based partly on Gerard’s work, as well as the 1931 film adaptation, cemented the pasty, bloody-fanged vampire we know today into pop horror consciousness.LiveScience, last year, related the following about vampires and vampire myths:
The vampires most people are familiar with (such as Dracula) are revenants — human corpses that are said to return from the grave to harm the living; these vampires have Slavic origins only a few hundred years old. But other, older, versions of the vampire were not thought to be human at all but instead supernatural, possibly demonic, entities that did not take human form.
Matthew Beresford, author of "From Demons to Dracula: The Creation of the Modern Vampire Myth" notes that "There are clear foundations for the vampire in the ancient world, and it is impossible to prove when the myth first arose. There are suggestions that the vampire was born out of sorcery in ancient Egypt, a demon summoned into this world from some other." There are many variations of vampires from around the world. There are Asian vampires, such as the Chinese jianshi, evil spirits that attack people and drain their life energy; the blood-drinking Wrathful Deities that appear in the "Tibetan Book of the Dead," and many others.
The same article notes:
The belief in vampires stems from superstition and mistaken assumptions about post-mortem decay. The first recorded accounts of vampires follow a consistent pattern: Some unexplained misfortune would befall a person, family, or town — perhaps a drought dried up crops, or an infectious disease struck. Before science could explain weather patterns and germ theory, any bad event for which there was not an obvious cause might be blamed on a vampire. Vampires were one easy answer to the age-old question of why bad things happen to good people.
Villagers combined their belief that something had cursed them with fear of the dead, and concluded that perhaps the recently deceased might be responsible, having come back from the graves with evil intent. Graves were unearthed, and surprised villagers often mistook ordinary decomposition processes for supernatural phenomenon. For example, though laypeople might assume that a body would decompose immediately, if the coffin is well sealed and buried in winter, putrefaction might be delayed by weeks or months; intestinal decomposition creates bloating which can force blood up into the mouth, making it look like a dead body has recently sucked blood. These processes are well understood by modern doctors and morticians, but in medieval Europe were taken as unmistakable signs that vampires were real and existed among them.
Theodora Goss writes about vampires at Realms of Fantasy, discussing the myths (primarily focusing on Romanian) and the modern literature. Among other things, she relates the following account of vampirism:
The following account of one such attack was published in Ion Creanga, the Romanian journal of folklore, in 1914:
Some fifteen years ago, in Amărăşti in the north of Dolj, an old woman, the mother of the peasant Dinu Gheorghiţa, died. After some months, the children of her eldest son began to die, one after the other, and, after that, the children of her youngest son. The sons became anxious, dug her up one night, cut her in two, and buried her again. Still the deaths did not cease. They dug her up a second time, and what did they see? The body whole without a wound. It was a great marvel. They took her and carried her into the forest, and put her under a great tree in a remote part of the forest. There they disemboweled her, took out her heart, from which blood was flowing, cut it in four, put it on hot cinders, and burnt it. They took the ashes and gave them to children to drink with water. They threw the body on the fire, burnt it, and buried the ashes of the body. Then the deaths ceased.She also discusses some of the "rules" from Romanian myths on how to tell if a corpse has turned to a vampire, and how to "kill" a vampire.
For those interested, Wikipedia has a list of myths or vampire-type creatures from around the world.