The Croatoan Virus, also dubbed "Croatoan", is a demonic disease in the Supernatural universe that infects people and turns them into murderous zombie-like creatures called "Croats" with varying degrees of intelligence, ranging from cruel and cunning to savage and mindless. It is transmitted through blood to blood contact. However Sam Winchester is shown to be immune to its effect. Lucifer, Azazel, and Pestilence hoped to use this virus to wreak havoc on Earth during the Apocalypse, but it was averted by Sam, Bobby, Dean and Castiel. Those with demon blood are immune to this supernatural illness of demonic origin.