Zombie Infection

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This article is about the official game mode. For community versions with a similar name and concept, see Zombie game mode.
Murky's swamp town.
Huddle up, humans- but not too close, you never know who will turn...
Zombie Infection publicity blurb

Zombie Infection is a community-created game mode added in Scream Fortress XV with the October 9, 2023 Patch. It features the RED team (also referred to as "Humans" or "Survivors") fighting to survive against the undead hordes of BLU team Zombies.

Introduction video


At the start of a round, all players begin on RED team and are given a small period of time to prepare their defenses. After this, a certain number of players based on the amount of players on RED team are randomly chosen to become infected. When a RED player dies, they are moved to the BLU team and play as a Zombie. BLU team wins if they manage to infect all Humans, while RED team wins if the remaining Humans hold out long enough without all being infected. Eight seconds are added to the timer for each RED player that is infected.


  • When there are 3 Humans left, all surviving Humans deal Mini-Crit damage.[1] When there is 1 Human left, the last surviving Human deals full Critical hits.[2]

Weapon modifications


  • Zombies are mostly limited to only using melee attacks (doing 65 base damage), however, each Zombie class features a unique ability or passive.
  • Zombies cannot deal Critical hits, pick up Ammo or Health packs, and do not drop ammo on death (except for the Engineer if he has an unused EMP grenade).[4]
  • Zombies never take fall damage.[5]
  • Except for Heavy and Scout Zombies, if a Zombie is not considered in combat, they receive a small movement speed buff. This goes away after hitting a Human or being hit by a Human.[6]
  • All Zombies wear a Voodoo-Cursed Soul, have a green footstep Halloween Spell effect, and have a voice modifier applied that deepens their voice.
  • Zombies explode on death and drop a small health kit (Zombie Pyros do not drop a health kit).[7]

The number of starting Zombies is predefined for each team with less than 18 players. For teams with 18 or more players, it is calculated by rounding up the result of the number of RED players divided by 5.

RED players Nº of Zombies
1 – 4 1
5 – 8 2
9 – 12 3
13 – 17 4
18 4
19 4
20 4
21 5
22 5
23 5
24 5

Zombie abilities

Class Abilities Cooldown HUD icon
Icon scout zombie.jpg Zombie Scout Speed Demon

Pictogram plus.png  Passive: 75% faster movement speed (520 Hu/s) and 25% extra jump height.[8]
Pictogram plus.png  Passive: Triple jump.[9]
Pictogram minus.png  Passive: 50 less max health (75 total max health).[4]

N/A Scout Zombie Infection ability.png
Icon soldier zombie.jpg Zombie Soldier Pounce

Pictogram plus.png  Ability: Leap into the air, in the direction the player is looking. Landing on a player's head results in a stomp similar to the Mantreads.
Pictogram info.png  This leap counts as blast jumping.[10]
Pictogram plus.png  Passive: 25 extra max health (225 total max health).[4]

5 seconds[11] Soldier Zombie Infection ability.png
Icon pyro zombie.jpg Zombie Pyro Hellspawn

Pictogram plus.png  Passive: Immunity to all flames and liquids. Explodes into flames and leaves a Gas Passer cloud when killed.[12]
Pictogram plus.png  Passive: Every hit ignites Humans for a total of 3 seconds, dealing 8 damage per second.[13]
Pictogram plus.png  Passive: On death, no health kit is dropped.
Pictogram plus.png  Passive: 25 extra max health (200 total max health).
Pictogram minus.png  Passive: 30% damage penalty.[14]

N/A Pyro Zombie Infection ability.png
Icon demoman zombie.jpg Zombie Demoman Blast Charge

Pictogram plus.png  Ability: Explosive Charge, similar to the Charge when wearing a shield, dealing 275 damage in a 150 Hammer unit radius.[15]
Pictogram plus.png  Passive: 25 extra max health (200 total max health).[4]

6 seconds[11] Demoman Zombie Infection ability.png
Icon heavy zombie.jpg Zombie Heavy The Tank

Pictogram plus.png  Passive: Deals 220% damage, immune to knockback and critical hits,[14] 35% damage resistance, 50% resistance to Sentry Gun damage, and increased knockback dealt.[16]
Pictogram plus.png  Passive: Instantly destroy buildings in a single hit.[4]
Pictogram plus.png  Passive: 300 extra max health (600 total max health).[4]
Pictogram minus.png  Passive: 10% slower move speed (207 Hu/s).[4]

N/A Heavy Zombie Infection ability.png
Icon engineer zombie.jpg Zombie Engineer EMP Grenade

Pictogram plus.png  Ability: Throw an EMP bomb, temporarily disabling any buildings for 6.5 seconds and doing 110 damage after 3.5 seconds in a 500 Hammer units radius.[17]
Pictogram info.png  EMP explosion shakes the screen of players near it.[17]
Pictogram plus.png  Passive: 25 extra max health (150 total max health).[4]
Pictogram minus.png  Passive: If an Engineer dies with an unused EMP grenade, he drops a medium ammo pack.[18]

10 seconds[11] Engineer Zombie Infection ability.png
Icon medic zombie.jpg Zombie Medic Heal

Pictogram plus.png  Ability: Heals and ÜberCharges himself and teammates in a 275 Hammer units radius around him.
Pictogram info.png  The healing and ÜberCharge effect is identical to the Overheal magic spell.[19][20]
Pictogram info.png  Forces the player into a third person perspective when used, but still allows attacking, even during the ÜberCharge.
Pictogram plus.png  Passive: 25 extra max health (175 total max health).[4]

7 seconds[11] Medic Zombie Infection ability.png
Icon sniper zombie.jpg Zombie Sniper Spit

Pictogram plus.png  Ability: Spit an acid ball that, when it lands, damages any Human and building that stands on it.
Pictogram info.png  The initial acid ball hit deals 45 damage and the acid pool deals 25 damage per tick (50 damage per second) and stays for 5 seconds.
Pictogram info.png  The acid pool has a 130 Hammer unit radius.[21]
Pictogram info.png  The acid ball can be held for a maximum of 5 seconds.[21]
Pictogram plus.png  Passive: Drop a pool of acid on death.
Pictogram plus.png  Passive: 25 extra max health (150 total max health).[4]

5 seconds[11] Sniper Zombie Infection ability.png
Icon spy zombie.jpg Zombie Spy Reveal

Pictogram plus.png  Ability: Mark Humans in a radius around him, revealing their location with an outline.
Pictogram info.png  It has a radius 1000 Hammer units and reveals Humans for 20 seconds.[22]
Pictogram plus.png  Passive: Automatically cloak. Attacking or using Reveal uncloaks the Zombie Spy for 3 seconds.
Pictogram plus.png  Passive: 10 extra max health (135 total max health).[4]

10 seconds[11] Spy Zombie Infection ability.png


Main article: Community Zombie Infection strategy


Main article: List of maps

Zombie Infection maps carry the zi_ prefix; community maps are identified with an italic font.

Name Picture File name
Atoll Zi atoll.png zi_atoll
Devastation Zi devastation final1.png zi_devastation_final1
Murky Zi murky.png zi_murky
Sanitarium Zi sanitarium.png zi_sanitarium
Woods Zi woods.png zi_woods

Update history

October 9, 2023 Patch #1 (Scream Fortress 2023)
  • Added maps: Atoll, Devastation, Murky, Sanitarium, and Woods.

October 13, 2023 Patch

  • Updated zi_murky, zi_atoll, zi_devastation_final1, and zi_sanitarium[23]
    • These changes are aimed to make playing as a Zombie more engaging, and to weaken the Human meta of bunkering without hurting their ability to roam and fight
      • Zombie Spy is now passively cloaked, only losing his cloak for 3 seconds when attacking or using his "Reveal" ability
        • This change will allow Zombie Spy to circumvent Sentry Guns that are watching large areas, and allow him to sneak into or around strongholds
      • Zombie Soldier's "Pounce" ability is now significantly higher, and has a 5 second cooldown (from 8)
        • These changes will bolster Zombie Soldier's role as a Recon pick and a roof buster, capable of launching through sentry fire
      • Zombie Sniper's "Spit" ability now damages buildables
      • Zombie Sniper now drops a puddle of spit on death
        • Both of these changes will make you feel like you're contributing more with your spit, and if that's not enough, you at least get to drop one on death to cause a small area of denial
      • Zombie Pyro no longer drops small health kits
      • Zombie Pyro's "Hellspawn" passive now releases a flaming explosion on death on top of the existing Gas Passer cloud
        • These changes should strengthen their afterburn capability, and make them a scarier threat if you let them too close
      • Zombie Heavy's "Tank" ability now adds the Battalion's Backup buff (immunity to Critical hits, 35% resistance to regular damage, and a 50% resistance to Sentry Gun damage)
      • Zombie Heavy deals 20% increased melee damage
        • Sentry and Crit resistance will bring Zombie Heavy's effective hp up much higher, buffing his role as a tank that you really oughta stay away from. His slower speed is unchanged, so you're still able to run. The changes will just make bunkering much more difficult with him around.
      • Zombie Engineer's EMP no longer rolls on shallow surfaces, and now does 110 damage instead of fractional damage
        • This change will turn EMP grenades into a much more immediate threat, instantly breaking mini Sentry Guns, crippling level 1 Sentry Guns, and wounding other buildings
      • Zombie Scout's "Speed Demon" passive now comes and additional 25% jump height boost
        • Zombie Scout already has a triple jump, but increasing jump height will make him even more of a pest buzzing around your head, and better at climbing onto roofs once a hold is destroyed
      • 1/5 of the server will be converted to zombies at the end of setup (from 1/6), and will also round up
        • It's become clear that there simply aren't enough zombies selected at the start of the round. Initial pushes should be easier to perform with a couple more units.
      • Sentry Guns deal 40% damage to zombies (from 60%)
        • Engineers are simply way too oppressive. The Dispenser is invaluable for the sake of ammo, and the sentry still has use as a knockback tool, but now should be significantly less frustrating to play against.
      • Demoman shield items no longer halve the damage taken by zombies
        • He was just too strong and incredibly unfun to duel. The extended reach of swords is already amazing against melee-only characters. His strong maneuverability is unchanged.
      • Zombie Medic Heal cooldown reduced to 7 seconds (previously 11)
      • All Zombies except for Scout, heavy, and Spy, now have +25 HP (from +10)
    • Fixed a bug where Zombie Demo could detonate himself before the charge had started
    • Fixed a bug where Bonk! Atomic Punch could persist through Zombie conversion
    • Fixed various issues caused by Zombie Demo surviving his own charge
    • Fixed issues with the Zombie HUD not correctly displaying certain strings
    • Fixed exploit related to adding additional time
    • Added additional HIDEHUD bits to remove irrelevant HUD elements when playing Zombie
    • Added an instructional video (Thanks Funicular!)

October 19, 2023 Patch

  • Updated zi_murky, zi_atoll, zi_devastation_final1, zi_woods, and zi_sanitarium
    • If a game is in progress and there are no players on BLU team or RED team the game will now end
    • Fixed a bug that allowed Dead Ringer Spies to die without triggering a round loss
    • Fixed a bug that caused Zombies to not see combat text correctly
    • Fixed a bug that caused Rocket Launchers and Sticky Bomb Launchers to start with a low ammo
    • Fixed a bug that caused changing player loadout to kill human players (particularly on Murky)
    • Fixed an issue with missing particle effects for Medic's Heal ability
    • Adjusted the number of Zombies selected at round start for low player counts
    • Corrected unintended changes in the last update
      • Changed the damage dealt by Zombie Soldier's Stomp
        • In the previous update, Soldier would instantly kill his stomp target. This was not intended
        • The new damage calculation is (10 + fall damage x 3). This is the same as the Mantreads
      • Changed the Sentry Gun to deal 40% damage to Zombies
        • In the previous update, this was 35%. This was not intended
      • Added a sound effect to Pyro's explosion of flames on death
      • Removed some debug print statements
    • Reworked Demoman's Blast Charge to fix several exploits and bugs
      • These changes should also make Blast Charge more reliable and less frustrating to use
    • Blast Charge is now triggered based on the player's velocity
      • When player's speed drops below a threshold while charging, they explode
      • Additionally, anything that would usually interrupt a shield charge will now trigger the explosion
    • Fixed a bug that caused ÜberCharge applied by Blast Charge to persist longer than intended
    • Fixed a bug that caused Blast Charge to fail to kill the player in situations where the player should be killed
    • Fixed a bug that caused Blast Charge to briefly display the player's first person view before detonation
    • Fixed a bug that caused the player to be unable to attack, jump or duck after surviving Blast Charge
    • Fixed many bugs that caused Blast Charge to fail to detonate
    • Fixed many bugs related to Blast Charge being cast at the same time as being converted to Zombie

July 18, 2024 Patch #1 (Summer 2024 Update)

  • Updated zi_intro.webm media file.


  • Afterburn caused by the Pyro Zombie's on-hit ignite does not trigger hitsounds.[24]
  • Sometimes, the following bugs may happen:
    • The game mode's HUD elements do not load, and a large black or white line appears diagonally across the screen instead.
    • The first person viewmodel arms do not load.
    • The Voodoo-Cursed Soul and/or green footstep Halloween Spell effect ends up somewhere on the map, not attached to any player.
      • These effects may also merge with the player upon changing rounds, even as a Human form. This can also obstruct first person viewmodels if they are attached to the player. The Voodoo-Cursed Soul merged with a player does not match the class they are currently playing as, instead it is the Voodoo-Cursed Soul of the class they were in the previous round.
  • The Thriller taunt has a chance to replace the Heavy Zombie's High Noon kill taunt, when it does not normally replace kill taunts.

Unused content

  • Zombies under the effect of Jarate were originally meant to take Critical hits instead of Mini-Crits, as suggested by some commented out code.[25]



Pictogram comment.png When updates release, the code will likely have shifted a few lines or have moved somewhere else entirely.

  1. Chat message when 3 Humans are left.
  2. Chat message when 1 Human is left.
  3. a b c d vscript\infection\infection.nut:L563-670
  4. a b c d e f g h i j k vscripts\infection\const.nut:L167-210
  5. vscripts\infection\infection.nut:L525-526
  6. vscripts\infection\infection.nut:L516-531
  7. vscripts\infection\infection.nut:L378 (gib explode) and L360 (gas passer drop)
  8. vscripts\infection\const.nut:L99
  9. vscripts\infection\think.nut:L151
  10. vscripts\infection\ability.nut:L225
  11. a b c d e f vscripts\infection\const.nut:L17-28
  12. vscripts\infection\infection.nut:L349
  13. vscripts\infection\infection.nut:L695-713
  14. a b vscripts\infection\const.nut:L42-50
  15. vscripts\infection\ability.nut:L64-67
  16. vscripts\infection\const.nut:L229
  17. a b vscripts\infection\ability.nut:L10-29
  18. vscripts\infection\const.nut:L334-335
  19. vscripts\infection\ability.nut:L59-62
  20. vscripts\infection\ability.nut:L320
  21. a b vscripts\infection\ability.nut:L32-50
  22. vscripts\infection\ability.nut:L53-56
  23. zi_woods was updated too, but not mentioned
  24. Video showing bug.
  25. vscripts\infection\infection.nut:L548