Originally, the Infection mode came in with Halo 3, later being featured in Halo: Reach. It starts with one player being the “infected” with their goal being to kill everyone not infected. If you get killed by an infected, you yourself become one. Halo 4 also featured an infection mode, though it was called ‘Flood’ and had some slight differences.
343 have been adding a lot of new playlists to the games since its launch, including the more recent Action Sack which has seen a lot of players since its arrival.
“Since its release, it’s been consistently ranked towards the top, and for a few days this past week, it even saw more players than any other playlist,” 343 said. “While featured playlists generally draw in a substantial crowds during their first few days, we wouldn’t be surprised to see it continue to do well, and hope that you’re enjoying the wacky and often nonsensical chaos it offers.”
“The playlist team continues to work on future updates, and it’s quite likely that we’ll be talking more about things like Infection in the coming weeks. It’s also quite likely that I will continue to try and persuade the playlist team to put in a Head-to-Head playlist, and that they’ll continue to say “maybe” after a long hesitative pause.”
343 are keeping an eye on the feedback from players, but it seems likely that in the near future players can expect to play infection once again.