The Virus is a commonly used name for the disease that began the 1st Undead war. This war ended World War II in Europe, and put Germany on the edge of total destruction and extinction. The virus gives sufferers an insane need to eat living mea,t but also puts them into a semi-comatose state where they can no longer talk, rationally think, have emotions, or feel pain. Because they can not feel pain, the only way to kill a sufferer is shoot them in the major arteries, lungs, brain or heart. Because of the effects of the virus, they can only stumble or walk.
The Virus began when a truck full of a new biological weapon crashed as it tried to avoid hitting a dog that ran onto the road. The driver's efforts were in vain, hitting the dog anyway. This dog was infected with rabies. Because the German biological weapon was released, the rabid dog was infected with the agent. The two diseases melded, and the combination resulted in a semi-comatose state connected with all the symptoms of rabies. The dog became semi-comatose, but was aggressive, combative, and highly sensitive to touch and other kinds of stimulation. It moved to attack an onlooker, biting him and the walker struck the dog down, killing it. This man, referred to by authorities as Patient Zero, thought nothing of the bite of the dog, other than the need for a simple antiseptic.
Within weeks, he exhibited symptoms of the Virus, but his casual contact had spread the infection widely in the region. By the time, the German authorities realized the scope of the infection, its resultant infection rate, and its mortality, there was no way to stop the infections from spreading.