For all who don't know there are basically 4 types of infected all of which lethal in a different way. the first have only been infected for 48 hours or two days and have slightly impaired vision and a human conscious but a pack mentality and a lethal agression, dubbing them the name runners. the 3rd stage takes place after say a year or two and the infection has grown out of their heads and hardened, as a result they hunt with echolocation and kill with one hit. he 4th stage is basically after death where tyhe infected find a dark corner and decompose launching a mass of spores into the area to further infect passer bys.
I have little to know idea what the second type of infected could be. Runners are a speed chalenge and clickers are poweful, so what enemy type is left? I think human enemies cover projectile, so any guesses on what to expect from the un-announced 2nd stage of infection.