Has we didn't see Merle dead on the floor, but we saw the Gov shoot Merle we can assume he was killed by the gunshot wound, Merle must have turned without being bitten.
The Governor didnt shoot Merle in the head on purpose so that a walker would bite him and then Rick's group would find him when they got to the location as a zombie.
If someone dies or is killed, unless they are shot in the head they will turn (regardless if they are bitten or not)because the virus (as we learned from the CDC Doctor at the end of season 1) is in everyone.
Hey Cardi, how the heck are you? I was worried that maybe Michonne took you and was using you for her pet or something.
Glad to see you're a WD fan. One of my favorites. Hope all is well with you.
TIS
