Zombie Outbreak
For years, several hundred people have talked of how zombies might come about. They usually mention these horrible creatures as half dead, rather stupid, brain chasing, semi-clumsy, violent creatures. They also usually talk about how these creatures spread their disease by biting or getting their internal fluids combined with that of another human.
A rather harsh notion of the Zombie outbreak is that it's a virus; not just a disease, but a virus that must pass through the system of be alleviated by the immune system in order to be removed. Like several virus's however, some never leave the body, and if improperly dealt with, these virus's can lead to a permanent or chronic condition in the body.
Zombie diseases are also usually represented as being able to pass from humans to animals. These normally afflicted creatures are rabid, violent, and quite usually in an unusual state of mind, willing to harm other creatures at random or closely related to them.
Another idea of zombies is that not everyone becomes a zombie; some people die. This idea generally makes it slightly harder for the disease to be spread.
If this disease mutates, grows stronger, or the symptoms or ability to contract the disease grows stronger... we must just have a zombie outbreak.
Zombie Virus.