The Undead virus is the disease that caused the Outbreak. Those who contract the disease, which is transmitted through a bite from someone who is infected, suffer some symptoms before dying. As time goes on, they turn more pale and begin to cough up more and more blood. Their breathing also becomes shallow, and they are very weak. Their eyes roll up in the back of their heads, and then they die. Shortly after dying, they come back, and become zombies, more commonly known as "the undead." It is yet unknown how, who, and when it was first to infect anyone but it´s known that the deasease began in Indonesia by experiments between USA and Japan but this is just a theory. Considering the possibilities, there may be no known reason how it was first to infect any human, but because there is a short time between death and coming back it is very easy for many people to become infected.