Outbreak was a new co-op game mode available for one month in early 2018. There is no news as to when or if it will indeed come back out, but at this time it is unavailable to players.
Outbreak places three Operators on a map filled with infected creatures. An alien disease created five different hostiles, each with unique abilities. Each map (Resort, Hospital, and Junkyard) has several sections that must be loaded once everyone reaches a safe room. Make it to the end to win the game! This is basically if Rainbow Six Siege crossed over with Left 4 Dead.
Only one of eleven Operators can be chosen in this game mode: Ash, Tachanka, Doc, Smoke, Buck, Kapkan, Glaz, Ying, Finka, Lion and Recruit.
The five unique infected hostiles include Grunts, Smashers, Breachers, Rooters, and Apex. If this game mode ever returns, I will fill out this section to help out players.