In 2004, a well known strain of the Influenza A virus, H5N1 mutates. The results are deadly, as the virus causes extreme changes to the victims body and mind. The virus first acts like a normal case of flu for several hours or days, preventing easy detection and allowing the virus to spread long before victims enter the final stage. Once the flu has set in, victims undergo a process of "Zombiefication", causing distress, panic, violent tendencies and a taste for human flesh. This new strain became known as "H5N1Z".