Today, I've added the first new zombie into the game, putting us at a grand total of 5 different infected types at just past 48 hours after the Early Access launch.
He is slower than the rest of the infected, but he will try to latch onto the player and does a bit more damage the the others. As always, after he makes an appearance in your game for the first time, hop over to the forums if you have any feedback on whether or not you like how he is implemented and if any changes need to be made.
I expect to have at least one more new infected added into the game shortly. Keep an eye out!