After watching almost 5 seasons of The Walking Dead I expected that some of the mystery gets be revealed about "authors" of the virus and how it spread, but apparently the producers are not going to do that unless it happend in season 6. Are they going to reveal how the virus spread and who made it?
Quite possibly no.
He then went on to say:
So he knows how the zombie outbreak started, but he never considered it interesting enough to be the main focus of the show.
Given this, it's possible we'll never have the reasons revealed - it's impossible to tell right now.