The Real-Life Diseases that Spread the Vampire Myth
In this article found on the BCC, they briefly discuss a few theories as to what started the widespread belief of vampires in Eastern Europe. Nutrient deficiencies, rabies and other diseases caused by animal bites, porphyria, and catalepsy could all have seemed supernatural and evil to people with no knowledge of science. They also mention how stories of people suffering with these conditions could have ended up in large city news papers such as London and Paris, hence spreading the myths.