Scientists have suggested certain medical reasons behind vampirism. A rare disease known as catalepsy puts its victims into a death-condition, which could last for certain  periods of time. During the times when medical standards were not as advanced as it is now, people suffering from this disease may be considered dead and buried by their relatives. When the person aroused from his/her comatose, they would find themselves trapped and buried in a coffin. The sounds coming from the coffin is actually the sound of the victim trying to escape. The victim would eventually die of contorted positions of such an unfortunate soul when the coffin is finally opened.
 
A congenital blood disorder known as iron-deficiency porphyria was also offered as an explanation for vampirism. People suffering from this deficiency are unable to efficiently combine iron with porphyries to yield haem, which is an intrinsic component of the blood pigment hemoglobin. People suffering from this condition are extremely sensitive to the sunlight, which may cause skin disfiguration. Such people may be forced to drink the blood of normal people to increase iron intake.
 
Missing corpse were blamed on grave robbers and outbreaks of vampirism blamed on plague and other contagious diseases.
 

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