Swamp Fever

Swamp Fever is a new campaign which takes place in a "swampy" location in Left 4 Dead 2, according to Valve the Survivors will reach this swamp after evacuating from Savannah, it is believed to be the third (most likely) or fourth campaign. It will be first revealed to the public in Comic Con 2009 through 23rd July to 26th July and will be fully playable to the public views in the Left 4 Dead Demo which will take place near November 2009. It seems as though it's a showcase for the AI Director's new, more in-depth level controls—such as the weather, and the new water system which slows the Survivors down and does not allow them to run.

Swamp Fever is also the only campaign that will contain the new uncommon Mud Men infected, which are hard to spot, fast, and upon hit they spit mud, so your view becames worse and worse right to the under-boomer-vomit's level.

Trivia

 * Swamp fever is a term given to a number of diseases that are acquired in wet, swampy environments.
 * Unlike The Parish, Swamp Fever ends its finale the same way all the other Left 4 Dead campaigns does -- that is, calling a rescue and waiting until arrival.
 * Shanty House Walls in the finale can be broken off with weapon damage
 * The Spitter was first revealed in a video of Swamp Fever Gameplay
 * In the video of this level you can see a man hanging from a parachute this may be a reference to Shi No Numa in COD:WAW, and an OXM article says that they are creating on the level randomly, with help of the Director, and have some pills, weapons, ammo packs e.t.c with them.
 * It looks like at least in the Swamp Fever campaign you can choose between the old t1 and t2 weapons and new ones.