The article, Difficulty, has been requested for deletion by one of the editors in the wikia.
The reason is: Ill-factual article.
Each difficulty has different zombie spawn rates and rewards. [Plz add to this, not accurate so you're welcome to edit]
Easy
Reward:100$ - 175$
Infected Chance:20%
Start Infects:2 - 4
Medium
Reward:200$ - 275$
Infected Chance: 30%
Start Infects: 4 - 6
Hard
Reward:300$ - 375$
Infected Chance: 40%
Start Infects: 6 - 8
EXTREME
Reward:400$ - 500$
Infected Chance: 50%
Start Infects: 8 -10
Special Cases
King Cake:EXTREME (Always)
Reward:Varies
CTF:EXTREME (Always)
Infected Chance: 60%
Start Infects:8-10
Reward:470$ - 500$
SBF, FFA, and MMA:Unknown (Always)
Reward:0$ -100$
Mixed Gamemodes
Trivia
The smaller the server, the more likely you will become an infected.
The harder the difficulty, the more likely players will spawn as special infected.
Place hasn't decreased the spawn rate of smokers ever since the Winter Games so spawning as a smoker is likely.
Crawlers spawn more in layby no matter what difficulty it is