The vampire – an undead figure who rises each night from his unquiet grave to feast on the blood of the living – has appeared since the time of the Ancient Greeks. While some of the sage old philosophers we still admire today might have lived into their 70s, life expectancy in Ancient Greece was thought to be around 28; centuries before sanitation, refrigeration and antibiotics, diseases were more prevalent and were far more likely to take people to an early grave.

But without a microscope to study these tiny assailants, communities in older times saw the hand of the supernatural in many diseases. Take porphyria, for instance, which affects heme, the chemical compound which helps make up the haemoglobin found in our blood. The patients suffer itching, rashes and blisters every time their skin is exposed to sunlight. In the very worst – and thankfully, very rare – cases, the gums recede from the teeth, making them appear far more prominent. Their bodily waste takes on a purple hue, like that of undigested blood. And the effects of sensitivity to light can be so severe that sufferers lose their ears and noses – a physiognomy echoed in the looks of vampires such as Nosferatu.