In the last episode Shane wonders how the two cop walkers turned with no bite marks.
Rick tells him scratches when Rick really knows that everyone alive is infected with the virus since it's airbourne. and upon death you will become a walker. The CDC guy told him and which is why the CDC guy gave up because he knows there is no hope.
When Rick killed the two guys in the bar he shot the first in the head then the other in the chest and upclose in the head to prevent them from turning into walkers.
If Rick knows all of this why is he not telling anyone and why did he have sex with his wife and get her pregnant?
Rick is Daniel Kemp and wants to become the worlds first Earth Emperor and he needs about tree fiddy.