Hunters

A Mutant Virus has taken hold that disrupts the immune system and alters it, killing any disease, injury or ailment that may inflict the host. The down side, the host must replenish their blood with another's in order to suppress the pain. It becomes an epidemic; scientist cannot find a cure before the virus would overtake humanity. A radical initiative is introduced. Contain the virus by eradicating those affected. Hunters, cull those afflicted. The hope is enough infectees will be killed to make the problem go away.