Milton is one of the Governor's right hand men and he studies zombies.
If you look really closely at the promo for "Say the Word"- next week's episode, you can see a walker biting milton on the lower arm. I DONT know if he gets bitten or not but it sure looks like it.
Look real closely around 0:27, you'll see a walker on his arm
btw we might see penny blake in this episode too as stated by kirkman :3