See also:
https://en.wikipedia.org/wiki/Preparedness_101%3A_Zombie_Apocalypse
And:
... the generation of a “Zombie virus” cannot be firmly excluded according to the currently available biological evidence ... In keeping with this conjecture, an interesting simulation of an imaginary Zombie outbreak reveals that most of the US population would turn into Zombies within one week from appearance of the first case ... the transformation of Rabies virus into a “Zombie virus” will always remain a tangible threat surrounding human future