Some bits of info (conjecture): [b]"Yharnam is the city of blood ministration."[/b] Blood seems deeply engrained in Yharnam culture, possibly due to their pioneering and marketing of blood transfusion. As the game introduction suggests, possessing the blood of a Yharnam citizen, by birth or transfusion, may be necessary for citizenship or even entry in Yharnam. It also appears to have religious significance. [b]"The blood makes us human, makes us more than human, makes us human no more."[/b] The "plague of beasts," which seems to cause uncontrollable aggression and later, rapid and dramatic mutation, seems to be a bloodborne disease and does not appear human-specific. It seems unclear how long the plague has been endemic to Yharnam, but it is reasonable to suggest that the city's blood trade has facilitated its spread. The ritualistic connotations of "The Great Hunt" suggests that the plague has had multiple periods of resurgence in the city. The plague also seems to have religious significance, as its transformative symptoms may encourage narratives of transcendence. [b]Hunters appear to be partially immune to the plague. [/b] When a boss is defeated the victory title mentions "blood transfusion." Infected blood may in fact strengthen hunters. As one of the trailers suggests, this immunity may be only temporary, or may be obtained artificially, as a hunter is depicted succumbing to the disease.