Swamp Fever - Left 4 Dead 2
Intro to Swamp Fever
Unfortunately the helicopter pilot turned out to have been infected and so had to be killed. The team are stuck in the middle of the alligator-infested swamps looking for a way out to get to New Orleans
Swamp Fever's UCI are Mud Men or 'Mudders'. These are little crawling Infected that look very similar to Jockeys, but without the characteristic noise. Thankfully they do not have the same effect, but will simply splatter mud on your screen if you let them get too close.