Swamp Fever

Swamp Fever is a new campaign spanning four chapters which takes place in a "swampy" location in Left 4 Dead 2 after evacuating from Savannah. The Survivors will reach this swamp and escape from it in a fishing boat familiar to the one in Death Toll. It was playable in Comic Con 2009 through July 23rd to July 26th. 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 Infected, Mud Men, which are hard to spot, and extremely agile compared to the other Common Infected.

Trivia

 * Swamp fever is a term given to a number of diseases that are acquired in wet, swampy environments.
 * Some of the walls in a shanty house found in Swamp Fever can be broken off with weapon damage.
 * Swamp Fever was the very first campaign to reveal the Spitter in gameplay videos.
 * In the video of this level you can see a paratrooper hanging from their chute. An OXM article says that they are randomly located on the level by means of the Director, and will signify item drops underneath.
 * Swamp Fever currently is the only campaign with 4 chapters, as opposed to the usual 5. However, it is supposed to have the same duration as 5 levels, so it feels like a 5 level campaign.
 * The Campaign's slogan, "the only cure is dying", is a reference to the fact that there is currently no known cure for the infection. Or could be a reference to the survivors being immune, and presumably the only ones which a cure can be conjured from.
 * All four chapters seem to have a Crescendo Event, with the exception of the finale.
 * The train the survivors start in some Swamp Fever videos appears to be removed the same way police car was removed from Dark Carnival, due to Dark Carnival's rescue vehicle being a helicopter.