Infection

Looking for the Flood Infection Form? Infection is a multiplayer gametype in Halo 3. It is the "official" Zombie mode after it's popularity as a custom game mode in Halo 2. The object of the game is for the humans to stay alive as long as possible using a starting Shotgun and/or other classic Zombie and various weapons around the particular map, while the Zombies try to infect as many humans as possible. The number of players starting out as Zombies ("Alpha Zombies") can be changed in the options, and are selected at random. When a zombie kills a human player, he/she is "infected" and thus becomes a zombie. When there is just one human left, he is declared "Last Man Standing", and a red triangle will show up on every other player's screen detailing his location. One way Infection is commonly played is that some players make maps with Forge where the humans have a "base" equipped with weapons and grenades, equipment and vehicles.

On October 31, 2007, a specialized Halloween matchmaking playlist was available, which played this game mode with precisely 13 players (it being an "unlucky" number).