In 2007, Dr. Alice Krippin modified the RNA of the measles virus in an attempt to cure cancer; the resulting Krippin Virus mutated out of control, killing millions and transforming those who survived beyond recognition into aggressive, nocturnal albino creatures with near-superhuman strength and a high metabolism. Despite their rage and drive to feed, they are also capable of mercy and affection, and have social bonds with one another. They mistrust, fear and hunt unturned humans for food.