@Xprimentyl
Seriously if you haven't read it, go pick up World War Z. As far as Zombie Apocalypse stories go, it's probably my favorite. Brooks went to a LOT of trouble to try and be accurate with how such a contagion would spread, talking to multiple first responder groups (police, EMTs, firefighters, etc) and doctors of various fields, and basically asked them "if everything were to collapse, how would it happen?" And then framed the collapse around the data they gave him. He doesn't explain EXACTLY how the contagion begins, but he does give a Ground Zero for where humanity thinks it first started, based on data. The how/why of the actual contagion itself, is left vague, and for me that's fine.
But Brooks actually considers things like "how would weather impact zombie survival? when things are frozen, is that good/bad for survivors?" "what happens as the zombies last for longer periods of time and their bodies continue to decay? " Stuff that I can't recall ever being addressed prior to that book.
Anyone that really loves the zombie genre, should read that book, if they haven't already. The audiobook is abridged sadly, and the stories it cut out, were most of my personal favorites, so I wouldn't recommend it. I mean, it's GOOD, don't get me wrong, but, it's one of the few novels that ONLY had an abridged audio adaptation, and I don't really know why. It's not that big of a book, and the stories left out really helped to flesh out the daily life of things. So it's a shame they removed them.
The actual book itself, the full version, HIGHLY recommended.