Infection

Looking for the Flood Infection Form?  Infection' is a multiplayer gametype in Halo 3 and Halo: Reach''. It is the official Zombie mode, modeled after zombie mode's popularity as a custom game in Halo 2.

The gametype splits players into two groups: the humans, who must stay alive for as long as possible, and the zombies, who must try to kill every single human. When a zombie kills a human player, that human player is "infected" and they become a zombie. When only one human remains in the match, that human is declared "Last Man Standing". Uninfected players use their chosen armor colors, while zombies wear all-black (in Halo 3) or all-drab (in Halo: Reach) armor. The number of zombies at the start of the match -- called "Alpha Zombies" or "initial zombies" -- can be customized using gametype settings, and in Halo 3, Alpha Zombies can be given unique traits.

Medals

 * Zombie Killing Spree - Kill five zombies without dying.
 * Hell's Janitor - Kill ten zombies without dying.
 * Infection Spree - Infect five humans without dying.
 * Mmmm Brains - Infect ten humans without dying.
 * Last Man Standing - Be the last human left alive in the round.
 * Is Quisnam Protero Damno - Kill fifteen humans without dying. (removed)

Halloween
On October 31, 2007, a specialized Halloween Matchmaking playlist was available, which played this game mode with up to 13 players (it being an "unlucky" number). This game type's popularity allowed it to become a "regular" among Double EXP Weekend games. It was repeated again on October 31 2008, but unlike other occasions, the October 31 2007, 2008, and 2009 ones were Ranked. The others were mainly Social.

Double EXP Weekend
On April 10th, 2008, the playlist came back for a Double EXP Weekend as Living Dead, also starting with exactly 13 players. Living Dead also appeared on the weekend of May 22 and on the 28th August. Living Dead is a Double EXP Weekend game with many games. Infection games have also appeared in other Double EXP playlists such as Turkey Day, the 2008 Thanksgiving weekend playlist.

Halo: Reach
Halo: Reach introduced a new variant of Infection, called "Safe Havens". Safe Havens is a hybrid between Infection and King of the Hill; areas on the map called "Havens" are randomly activated, and humans standing in Havens receive special traits. When a human enters a Haven, a countdown timer will start; when the time runs out, that Haven stops being active, and another one activates. The default Safe Havens settings halve humans' Damage Modifier outside of a Haven, and grant them invincibility while inside of one.

The gametype settings have also been updated in Reach. Humans can be given loadouts, and their traits inside of a Haven can be customized. Players that commit suicide can be forcibly converted into zombies. However, several settings -- including all Alpha Zombie customization -- have been removed. Reach 's default Infection settings have been changed accordingly; humans are now equipped with Sprint, while zombies are given Evade.

Reach introduced an official, eight-player Matchmaking playlist called "Living Dead". The playlist uses special variants of Infection and Safe Havens that have been customized for Matchmaking. (Specifically, loadouts have been disabled.)

General
result in you being killed often.
 * A team that regroups in a single area and holds their position in a well defensible location has a much higher chance of surviving.
 * Conserving ammunition is key in most Infection games.
 * Accuracy and shot placement are equally important; most players tend to aim for the one spot where it will do the most damage, the head. However, from long range, targeting this part of the body can be tricky, even though the head is less shielded and armored when compared to the rest of the body, it is also a small target. Shooting at the center of mass, the torso or legs, guarantee's better chances of success. In addition, jumping or crouching makes shot placement on the head difficult; the main body isn't as easy to conceal or dodge with.

Halo 3

 * By default, regular zombies use Energy Swords, hence has limited/short attack range, and cannot pick up weapons. As such, it is recommended for the player to be equipped with a ranged weapon such as the Battle Rifle or the Covenant Carbine.
 * If you are playing as a zombie, its a good idea to put on Active Camo, so you can sneak up unnoticed or stalk the humans from behind, making sure they don't see you.
 * Yet another tactic that the "living" use is called "baiting". The players gather in a small, confined space; preferably one with only one opening. Whenever the zombies' attacks lull, the players send out a freelancer, known simply as "bait". The "bait" will attempt to lure the zombies closer to the stronghold, where the trap is set off and the zombie is killed by overwhelming force.
 * Sometimes it is a good idea to commit suicide if your group is under assault by a large horde of zombies. Try to avoid using Spike, Plasma, or Firebomb Grenades to kill yourself, because the explosion could damage your teammates.
 * Try to not use Gravity Hammers or Energy Swords when possible, in most types the zombies have one or both of these weapons and such close range combat would

Halo: Reach

 * It is common practice to find an exploitable part of the map, camp there, and snipe out zombies using one's Magnum.
 * Zombies should avoid using Evade on small maps where players can die by falling, as they may, if Evading up a slope, go flying into the air and over the edge of the map.
 * Committing suicide to escape zombies will only lead to your immediate infection and the loss of a point.

Trivia

 * "Infection" is based on the popular custom gametype in Halo 2 known as "Zombies". Zombies was based on Team Slayer, with the Red team being Humans and the Green team being Zombies. The Humans could only use human weapons, and the Zombies could only use Energy Swords. The game began with just one or two Zombie players, who would attempt to hunt down and kill the Humans. When a Human was killed by a Zombie, they would have to change teams and become a Zombie. Since there were no facilities in Halo 2 Custom Games to limit what weapons each team could use or to force players to switch teams upon death, Zombie gametypes relied on honor rules.
 * New, easily-obtained Infection achievements were added to Halo 3 to promote the Mythic Map Pack. They are Delicious Brains and Zombie Repeller. Delicious Brains is awarded when the player infects two humans, and Zombie Repeller is awarded by getting two zombie kills as a human.

Related Pages

 * Infection Settings
 * Alpha Zombie
 * Hide and Seek
 * Save One Bullet
 * Safe Havens