And... I think that's what the guy at the CDC (or whereever they were before it self destructed) whispered in Rick's ear before he let them escape.
That's a good point, but I find it hard to believe seeing how when Rick killed Shane, when he turned around to see zombie Shane, Rick looked stunned. You would think he would know he'd come back in zombie form
I was thinking that he was telling Rick his wife was preggos