It is becoming clear that World War Z could have been prevented. Between ludicrous positioning of medical research labs and the less than stellar performance of the authorities, it's a wonder that humanity is not extinct.
We now learn that scientists had developed a model of a potential zombie outbreak before SHTF. This is documented in When Zombies Attack!: Mathematical Modeling of an Outbreak of Zombie Infection (pdf). The conclusion of this is quite prescient:
In summary, a zombie outbreak is likely to lead to the collapse of civilisation, unless it is dealt with quickly. While aggressive quarantine may contain the epidemic, or a cure may lead to coexistence of humans and zombies, the most effective way to contain the rise of the undead is to hit hard and hit often.
The inference in the paper is that the collapse of civilization is equivalent to extinction. It did not seem to occur to the authors that a new civilization would arise from the ashes, albeit one largely based on the world as we knew it. Truly, that which did not kill us, made us stronger.