Not buying the ''virus'' aspect
Inspiration was drawn from 28 days later of course to create the walking dead comic and series, so they borrow some aspects of the movie including the ''virus'' aspect. But those people were not ''dead'' they were infected with the rage virus and in a rabid-like state.
The situation is different when applied here.There is no virus that can reanimate the dead and even if there was they wouldn't have this ''super strong'' bite force as the human jaw and teeth are pitiful at biting and they would simply decay not posing much threat after a few years. Forget about ''TS-19'' (this wasn't even included in the comics either).
What made the walking dead so scary in its earlier seasons (or for some even now) is the unknown aspect of these creatures. They never die, they keep going, their bites defy anatomy and they almost always overpower (all you can do is run). Obviously this is purely supernatural.