Why does it have to be a virus? The same has been applied to vampires and werewolves and it's still just as messy and full of BS. Might as well just own up to the illogic and go back to calling it supernatural.
Because Ciph and myself were looking for rhyme and reason to it.
One of the fundamental cross fiction aspects seems to be that if one gets bitten by a Zombie and lives one later either becomes a Zombie or dies from the infection.
In WWZ a young Israeli soldier is saved after being bitten and then having her hand removed by amputation. Hence why it maybe a Viral element.
( Just for fun!! don't stress it !! )