Fever Swamp is a deadly swamp located somewhere in Florida.
The Werewolf of Fever Swamp
In the book The Werewolf of Fever Swamp, Will Blake mentions to Grady Tucker that the swamp gets its name from the fever it harbors. The fever will make the victim get hot like an oven before going insane and running into the swamp, never to leave. The swamp is also filled with deadly creatures, a bog that acts like quicksand, and a Werewolf.
Goosebumps HorrorLand (Video Game)
In the video game Goosebumps HorrorLand, Fever Swamp is the name of an area in HorrorLand. Unlike the titular swamp from The Werewolf of Fever Swamp, this version of Fever Swamp is one of HorrorLand's water parks. The park hosts magic shows that are run by Horrifico and feature The Great Gargantua.