The Department of Defense declassified the following document: http://www.scribd.com/doc/223872345/CONPLAN-8888 Discuss.
the zombie threat summary was inspired work. 8 types of zombies including cz or chicken zombies which are the only proven class of zombies. saves me a lot of time, I was just starting to recognize a few of the classes on my own.
Classified bioweapons already developed could turn people into "zombies" after release. Who knows. Perhaps like extreme rabies.