Short answers, pulled from the story.
Folkloric vampires were described as bloated, with ruddy, purplish, or dark skin, blood seeping from the mouth and nose, and one eye often left open in the coffin. They wore the linen shrouds of their burial and had no fangs; the gaunt, pale vampire only emerged in the early 19th century through literary fiction.
The panic began with alleged vampire attacks in East Prussia in 1721 and spread through the Habsburg monarchy from 1725 to 1734. Well-documented cases involving Petar Blagojević and Miloš Čečar led government officials to exhume and stake bodies; Empress Maria Theresa ended the controversy by sending her physician Gerard van Swieten to investigate, after which she passed laws prohibiting grave opening.
John Polidori published The Vampyre in 1819, making it the first highly successful prose fiction piece about vampires. Polidori was Lord Byron's personal physician and modelled the vampire Lord Ruthven on Byron. Bram Stoker's Dracula, published in 1897, later became the most definitive vampire novel.
The English word vampire, appearing in print as vampyre in 1732, derived from the German Vampir, which came from the Serbian word vampir in the early 18th century. The concept is almost universally accepted as rooted in Slavic languages, with parallel forms found in Turkish, Tatar, Bulgarian, Polish, Ukrainian, and other languages; a pagan worship of upyri is attested in Old Russian as far back as the 11th through 13th centuries.
Author Paul Barber linked vampire belief to the misunderstood process of decomposition: gases cause bodies to swell and look ruddy, blood seeps from the nose and mouth, and retreating skin creates the illusion of hair and nail growth. In 1985, biochemist David Dolphin proposed a link to porphyria, though this was later dismissed by experts. Neurologist Juan Gómez-Alonso examined rabies as a factor, noting that hypersensitivity to garlic and light, disrupted sleep, and frothing at the mouth are all symptoms of the disease.
The most recently recorded American case involved Mercy Brown, a nineteen-year-old who died in Exeter, Rhode Island, in 1892. Her father, assisted by the family physician, exhumed her body two months after her death, removed her heart, and burned it to ashes; the practice was tied to New England beliefs that tuberculosis was caused by the dead returning to feed on their living relatives.