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Common Infected

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See also: Uncommon Infected

Zombie 1
Common Infected
Health 50
Gender (infected) Male
Species Human infected
Abilities Climbing walls, Breaking doors
Attacks Punching, clawing, kicking.
Alternate names Infected, Vampires, Whiskey Deltas, Zombies, Walking Dead, Sons of Bitches.
"I ain't gonna let these god damn vampires beat me."
"Holy shit, zombies are real. I KNEW it!"

Common Infected (referred to in The Parish and The Sacrifice comic as Whiskey Delta, meaning Walking Dead, by the Military) are the most frequently faced members of the Infected, and the easiest to defeat.[1] Their strength lies in the fact that they attack in groups, more commonly referred to as the Horde, sometimes as large as several dozen.

While they seem capable of ignoring pain, they are as easy to kill as any normal human is. They are capable of climbing ladders and scaling objects once they find a target, and will not stop until it is dead. The default number of Infected that the Director spawns in a Horde is around 30. These Infected are fast, sensitive to loud noises and movement, and able to attack in ravenous waves, as determined by the Director. They might not notice The Survivors right away, but when they do, watch out—they're fast, and it won't take long for them to close the distance.

The Horde


Common Infected in Left 4 Dead 2.

The "Horde" is a term people often use as a reference, to a medium or large amount of Common Infected. A Horde of Infected can be powerful but they are not invincible by any means. These Hordes can often be distracted very easily in many ways. For example, the Survivors mainly attract the Common Infected via loud noises and bright lights.

There are several occasions throughout each campaign, called Crescendo Events, where the Survivors must do a certain action, such as opening an emergency door that will set off an alarm, or turning on a noisy generator, that alerts the Horde in order to proceed to the next segment of that chapter. There are also other times where the Survivors may accidentally alert them by setting off a car alarm, or if Re: Your Brains starts to play on a jukebox. All of these trigger a Crescendo Event. When a pipe bomb is thrown, all of the Common Infected in the immediate area will come to investigate the loud beeps and flashing lights, chasing the pipe bomb and clustering around it until it explodes, killing them. When the Common Infected attack from the front, they do approximately 1 damage on Easy, 2 on Normal, 5 on Advanced and 20 on Expert, and when they hit you in the back, they do half as much damage.

Appearances and Action

Common Infected come in variety of appearances, both male and female, such as patients, nurses, construction workers, military personnel, and airport staff, the differences only being cosmetic. They are the vulnerable victims of the vicious virus only known as The Infection, though referred to as "The Green Flu" by newspapers, TV, and on the Midnight Riders website that is sweeping through the area.

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A few of the new faces of the Infected in Left 4 Dead 2.

It seems that the Common Infected in Left 4 Dead 2 almost have the same base model, but with slight changes in hairstyle, clothes, and blood marks, while in the first game, there are many different models that stay the same. This is to save memory in the second game, so the Pipe Bomb would now create ragdolls and the Minigun/50cal being able to make gibs.

Common Infected do not differ in appearance from a sick human as much as Special Infected do. According to the game commentary, the developers designed multiple types of faces and bodies, and would have the computer pair them when spawning Infected, ensuring a variety of characters. This allows for "something around 1500 possibilities". Some Infected models can be seen in any scenario of the game, while others, such as the Infected patients in Mercy Hospital or airport custom officers in Dead Air, are only encountered at certain areas.

Fighting Common01

Two Common Infected fighting.

When not attacking, they are very vulnerable, usually sitting down, leaning on walls, or simply standing. Usually, when in this state, a Common Infected can easily be taken down instantly by a shove or melee attack; they must be unaware of the Survivors' presence to be taken down with one hit. They are easily provoked by light, sound, or touch, but are normally only dangerous in large groups or when completely surrounding a player. The heads, arms and legs can all be shot or cut off, this happening easiest with the use of a powerful gun or a slicing melee weapon.

The Infected react naturally to gunfire in their vicinity, turning towards the sound to attack the shooter. Shooting one in the foot will cause a very different reaction than shooting one in the chest with a Pump Shotgun. Usually, if an idle Common Infected receives a non-fatal gunshot wound from a distance they will writhe in pain and clutch the wound with their hands; but if they are running towards the player and receive a non-fatal gunshot wound they will just continue to pursue the player and ignore the pain. This can be most easily observed by shooting them with a Pistol.

They are often seen engaging in bizarre activities (e.g. vomiting, attacking inanimate objects, fighting each other, showing that the sickness may still be affecting them even in this state, even perhaps killing them rather than keeping them as Infected) when unaware of the Survivors, but begin to rush at the Survivors the very moment they see them. Very rarely, an Infected can be seen facing a wall and making mumbling noises, as if talking to itself. A Common Infected's attack slows down the target player, making it exceedingly difficult to run away from a mob of them that is close to you. They also seem to be at least smart enough to attempt to trap the player, commonly running ahead of him or her and attacking from in front to prevent movement, assuming there is also a Horde or something like a Tank behind the player.


A Horde climbing over a fence.

The Infected appear to lack a sense of self preservation, as they will actively charge into flames, explosions, jump off from high buildings, and against superior forces of the Survivors and their weapons, even if they have encountered these things before (this can be best observed by throwing a Bile bomb into a fire in The Hotel). A possibility is that the Infection has affected their brains to such a degree that they only think of spreading it, or may simply think of attacking anything that disturbs them from their vicinity. This could mean that the Infected ignore their injury, only to attack the Survivors.

When approached by a melee-wielding survivor, the Infected frequently dodge or duck from the attacks. The Infected also rigorously make flanking attempts, trying to hit Survivors from the sides or backs as to avoid danger. In addition, they also appear to be capable of many acrobatic actions, such as climbing fences, climbing walls, and many other actions to get at Survivors.

Sitting Zombie

An Infected sitting.

The Infected are not known to feed or drink, however, they can still survive, as in the first level of Dead Air, there is a piece of graffiti that says "They don't eat, they don't sleep, what keeps them going?", and it is possible that the Infection has removed the mental ability to perform these necessary life functions. This may indicate that the Infected may eventually die of starvation or dehydration, and possibly even exposure to the elements as the Infected do not seem to seek shelter in conditions that non-Infected would (the theme of the Infected dying out and repopulation commencing is similar to what happened following the events of the film 28 Days Later). However, it's possible that the Infected resort to cannibalism, as evident from the blood on their mouths. It is also possible that the Infected just bleed from their mouths, but it is more likely it is just blood from earlier victims.

Common Infected hair and skin pigmentation is usually very low, resulting in a pale gray skin, which explains the gray skin and white hair color of the Witches. Lesser Infected may also have pale hair, though some female Common Infected have dark, blond, or red hair. Some Infected, such as Boomers and Smokers, may have black or dark hair.

Location Common Infected

In both Left 4 Dead and Left 4 Dead 2, there are special Common Infected that are only found on specific areas or chapters in different campaigns. Unlike the Uncommon Infected, these Infected individuals only look different in appearance and do not have any special abilities.

Left 4 Dead


An Infected surgeon sitting on the ground.

No Mercy

In the final two chapters of this campaign, the Survivors come across Infected doctors and nurses as well as patients at Mercy Hospital. The hospital staff were trying to treat the Infected individuals; however, they too became Infected.

Dead Air

In the final two chapters of this campaign, the Survivors pass through Metro International Airport, encountering several Infected airport staff, such as TSA agents, baggage handlers, and airplane pilots as a result of when the Infection hit.

Left 4 Dead 2

The Passing

In Rayford Park near The Riverbank, there was a wedding ceremony at the time of the Infection. When the Survivors pass by, the wedding guests are seen still wearing their dresses and tuxedos. An Infected Bride Witch can also be seen left crying at the altar. Later in campaign, the Survivors will also encounter infected bikers and Midnight Riders fans.

Dark Carnival

At Whispering Oaks Amusement Park there are still members of the park staff seen by the Survivors. When CEDA converted the park into an evacuation center, they were assisting in the evacuation by directing civilians and trying to maintain a level of calmness with the public. However, due to the severity of the Green Flu virus, they too became Infected.

Hard Rain

There are hillbilly Infected in the town of Ducatel which are commonly mistaken for Chargers due to the fact that both of them wear the same type of overalls.

Swamp Fever

At Village En Marais, instead of the Common Infected covered in blood, they are covered in mud. They are not to be mistaken as Mud Men since the mud fully covers this Uncommon Infected and they walk on all fours.

Extent of Mutations


An Infected police officer.

Though the Common Infected have evidently been mutated the least physically by this strain of the Infection, the strain appears to have had a bigger effect on their minds. They seem to have lost many of their higher brain functions. However, their sense of smell and hearing have been greatly enhanced, possibly explaining things such as Crescendo Events and how the Infected are able to notice the Survivors from the littlest things, such as the Boomer bile. It's possible they've had very slight boosts in strength (as hinted by their capability to break walls and take a Survivor down in a few hits on Expert difficulty), speed, and endurance—though, again, it appears to be slight, as they don't withstand many bullets or hits in general. Perhaps due to loss of higher brain functions, they seem to ignore pain and damage even when their limbs are blown off.

An exception to this, is the Fallen Survivor from The Passing, which will run from the Survivors once shot, as opposed to other Common Infected. There seems to be little explanation for this behavior, other than the individual's will to survive surpassed the Infection or that they have a strain of it that affected their sense of self preservation less, though, despite this, they still seem not to notice wounds that would be fatal if left untreated, such as a severed limb. The Infected also tend to be incredibly hostile to anything not perceived as being Infected, although there are occasions when two Infected are seen fighting one another and even killing each other. Additionally, the bodies and bones of the Infected seem to have weakened, seeing how their bodies explode with blood when they are shot/chopped, compared with how a normal human being would react, and the fact that a Guitar can decapitate them. Overall, they seem quite animalistic in nature.

If nothing else, they seem to have some grasp of their current situation, or at least how they feel; generally, idle Infected act physically ill, holding their heads and vomiting as they shuffle around slowly. Occasionally, if you watch one long enough, one of the Infected who is holding their head may begin to writhe in pain, or they may simply lie down and sometimes die without being shot or punched, suggesting that the virus is deadlier than it seems. It is also possible that after Infection, they have a limited life span, just like how people Infected with rabies (the virus the game's virus was based on) have a limited lifespan if left untreated. It could also be through brain hemorrhaging, as Infected appear to bleed out the ears and eyes. This also explains why they hold their heads in pain. Another possibility is that these deaths may be the result of an injury that the Infected person received earlier, such as from a gunshot from other Survivors or from a fall that they endured. They are shown to have a primitive but working communication system with others, generally through grunts and screams. In the comic they are also shown to see the Survivors as something inhuman, or something of the sort, which may explain why they attack them. It may even be that symptoms of the Infection include immense hallucinations followed by adverse paranoia which leads them to attack nearly anything they see moving, including their own kind on various occasions.

Burned Infected

A set of burned Infected.

Ripped Infected

The end result of a close-range shotgun blast.

The mutation might have also caused a severe breakdown to the human anatomy, as it is observed while killing the Infected. They have their limbs cut off more easily than the normal state, and their bodies burn into ashes in only a few moments. Furthermore, their bodies become more fragile, making them vulnerable to damage, whether it is an outside force, or an internal damage. Melee attacks and simple shots do considerable damage to them, even killing them in the moment. Also, the anatomy breakdown is also shown in the case that if a Survivor would step on a sleeping Common Infected, they will immediately die.

Tactics and Tips

Common Infected are only strong in numbers. Sticking together is key to keeping them off you and your teammates' backs. If you are concerned about conserving ammunition, consider using the pistol, which kills them in just a few shots or in one head shot on any difficulty, not to mention it has infinite ammo. It is possible to kill a Common Infected simply by jumping on their heads. To do so, simply walk off an edge which is at least a little taller than the Common Infected, and onto their head. Hitting a Common Infected from behind can instantly kill them, and earn the player the SPINAL TAP achievement.

Players should ALWAYS be careful of any Infected lying on the ground. If it has been shot to death already, it should be ignored. However, some Commons tend to lie down, making it look as if they are dead. Shoot them, even if they look dead, because they can fool your senses and make several quick attacks if the player has not noticed them.

Closet mode

Left 4 Dead 2

The Horde as seen in The Parish

When a horde is about to attack, the best tactic is to back into a corner (preferably) or a wall. Assign the front two Survivors to crouch and melee continuously (not viable in Versus or Survival mode in Left 4 Dead) while the two Survivors behind them stand and fire their weapons at them. This works equally well when Survivors have been covered in Boomer bile. Finding the nearest door, closing it, and using a shotgun to blow out a significant chunk of it provides you with a shield that you can see through, as well as keeping the Infected from touching you—very useful for higher difficulties. The most important thing is limiting the area the Common Infected have to attack from. You may also throw a pipe bomb to divert the Infected if you have been covered in Boomer bile.

Note: This is not recommended for Left 4 Dead 2. This is because the Director will eventually spawn a Spitter or Charger that will force you away from your position. Ultimately, this will bring you out into the open, possibly surrounding the player with even more Infected. Also, a patch for Left for Dead's Versus and Survival modes (consequently passed on to Left 4 Dead 2 in all modes) implemented Melee Fatigue, which will force a short pause after five rapidly consecutive melee hits, and then after every hit until a 'cooldown' has been taken. The cooldown usually lasts anywhere from one to three seconds. However, Melee Fatigue can be negated for a short period of time by the use of adrenaline.

Remove Loners

Pick off wandering Infected that have strayed away from fellow Infected whenever you can. When entering a new area, swap to pistols or snipe via a hunting rifle or a sniper rifle and take out as many lone Infected as you can from the entryway as long as it stays quiet. The Director has a tendency to spawn hordes once you reach the mid-point of areas, and this "event" will cause any idle Infected in the area to attack as well. In Versus, however, it is unlikely the Special Infected will allow you to sit in one place long enough to clear a room in this manner, so keep moving.

In a safe room it is often a good idea to stay by the door and pick off any Infected that you can see. They can't hurt you if you're inside. This can make for an easier exit from the safe room.

Weapon of choice

Left4dead2 1a-1-

Coach and Ellis fighting off Infected in the Parish campaign

All weapons possess the ability to fire through multiple Infected, therefore positioning yourself so that the Infected are funneled into lines is effective.

Any shotgun can be very useful against the horde, as their shells deal large amounts of damage and can pass through multiple Infected. The Auto Shotgun and Combat Shotgun are slightly superior as shotguns go, as they can decimate groups in mere seconds, and there is no pause to pump the gun. A good tactic to use if they are coming through one area, such as a doorway, is to keep your fire pointed at the entry, as the Infected will be clustering together to get through, making them easier to kill. Remember to push the Infected back while reloading simultaneously taking into fact that the shotgun will take much longer to reload than any automatic weapons. It is also a good idea to aim low when using a shotgun against smaller hordes, since gibbing the legs is an instant kill towards Common Infected.

As far as automatic weapons go, the rifles can do major damage at any range. The Combat Rifle excels at accurate long-range shooting, but when a horde is in a player's personal space, it will lack the automatic fire and power to dispatch the Infected quickly. The AK-47 is the opposite; while it is poor at best at taking out distant enemies, its high power and low accuracy spread can clear out Infected in mid-to-close range. As for the Assault Rifle, its a medium grade in between both the Combat Rifle and the AK-47, it has a decent power and long range, fully automatic and good accuracy.

Given the Hunting Rifle or the Sniper Rifle, both should only be used to kill distant Infected. If need be, they can be used to kill attacking Infected with their high rate of fire. However, the rifles do excel at one thing: bullet penetration. If multiple Infected are being funneled through a tight area or are otherwise "stacked" (like when climbing an obstacle), the rifle family can shoot through several Infected with a single bullet. The scoped rifles can, however, instantly kill any Commons the bullet touches, making it useful on harder difficulties.

Power of the Horde

Left4dead 102908 18170-1-

Bill and Zoey fending off Common Infected in Dead Air.

The Common Infected are especially dangerous on the Expert difficulty. It can only take a couple of hits to down a Survivor, depending on the Survivor's current health. On this mode, the Common Infected also deal much more damage: 20 for each hit on the front, and 10 for each hit on the back. This means a Horde can easily cripple an entire team if they do not pay attention. The Infected often run up behind Survivors and hit them in the back, downing them before they can realize that they are being attacked. To avoid this, constantly watch behind you and look for Infected sneaking up behind your teammates, but do not shoot when they are close to Survivors to avoid friendly fire. Instead, melee them off, and then shoot. A good tactic is to always have someone watching behind the group. Communication is also key; always tell other Survivors when they are in danger. Also, it might be a good idea to hop on top of a car or van that has no alarm set because higher ground is usually recommended for fighting large amounts of Infected. However, if using the aforementioned tactic, make sure you've got your back to a wall or have your team cover all sides so the Horde can't sneak up behind you, as they can easily climb up and incapacitate you before you know it. Horde attacks also slow down players, and if they do not communicate this to other players, they can easily be left behind.

Darkness is your Friend

L4d matchmakingblog

Infected in the gloom

The Common Infected are obviously known to be attracted by the noise of car alarms and other loud sounds caused by most Crescendo Events, however, most have not realized the flashlight can also enrage Infected. Its effect is similar to that of a pipe bomb, as the bright, flashy lights irritate them, drawing their attention to the player. Flickering the lights on and off will disturb them faster. Using this knowledge may help if two of the Survivors have their flashlights on while the others do not, causing the two with the active flashlights to become focused on while their partners are able to break off the rest of the Infected.

In addition, the glare of the flashlight can sometimes cause your vision to focus directly at where the flashlight is pointed at. Shutting off the flashlight during a horde is usually a good idea, and practice using the silhouettes to identify Infected. In low-light situations this can drastically improve your vision of oncoming Infected. In addition, most Left 4 Dead 2 levels are in areas with generous light, yet shining your flashlight on the Infected will still disturb them. Use natural light whenever possible to avoid Infected.

Duly note that having a flashlight on whether it's day or night time and whether or not you shine it directly onto an Infected doesn't matter, it seems to aggravate them from anywhere nearby if the Flashlight is in sight. This kind of behaviour exemplifies the Common Infected's animalistic traits.

Playing smart

Although Common Infected are easily dispatched, it is still very important to eliminate them when possible and still pay attention to one's surroundings. In the event of a Horde or Crescendo Event, communication between players is necessary in order to avoid Special Infected ambushes and separation. Having a predetermined path and assigned combat roles can all contribute to a successful campaign or versus match. Also sometimes, when Infected are near a wall, their shadows can be seen through the walls, giving you a chance to plan or dispatch them before they become troublesome in a horde. When Tank is near, Common Infected could be a bigger threat than you think, not because they deal more damage or move faster, but they will distract you and your teammates and worse, block your escape route and make you an easy prey for the Tank.

Targeting priority

The Common Infected's targeting priority is:

  1. Thrown Pipe Bombs
  2. Survivors or Infected who are covered in Boomer bile
  3. Thrown Bile Bombs (that are not covering anyone)
  4. Survivors (Only during Hordes, Panic events, Crescendo events, Finales, or after they realize Survivors' existence).

Note: If players throw Boomer Bile or a Pipe Bomb, and other players are blocking the Infected from getting there, the Infected will start attacking Survivors instead, similar to when a Witch is unable to reach her target because someone is blocking her.

Notice that sometimes Common Infected will not switch their target when they are already attacking a Survivor. Survivors have to shove them to make them switch targets.

Infected tips

When playing as the Infected in Versus, you can use the Common Infected to your advantage. While the Survivors are attempting to reach the safe room, there are many ways you can exploit the Horde. Once the Survivors are occupied by the Horde, a competent Tank can defeat even the most organized Survivor team. Boomers can not only summon the Horde but also "extend" it by vomiting on the Survivors after they have dealt with the present Horde. Vomiting on downed Survivors is extremely effective and will very often result in death for the Survivor unless someone goes to help them deal with the Horde. Smokers are also effective during a Horde as they can snatch a Survivor and pull them away whilst the others are too busy fighting to help. Smokers can also be protected by the Common Infected. If you have snared a Survivor and you pull him in front of you where you can hit him, the Horde will attack along with you, killing them faster. This circle of Infected makes it harder for the Survivors to kill you. You can even do a substantial amount of damage with a Hunter before the Survivors can deal with the Horde and kill him. Other Infected will also surround the Hunter to claw at the Survivor. There are around 30 Common Infected within a Horde. During a Horde attack is the best time to work together, the Special Infected need to cooperate and doing so with the Common Infected can be fatal to the Survivors.


See Main Article: Achievements

Left 4 Dead

L4d pyrotechnician PYROTECHNICIAN (20G)
Blow up 20 Infected in a single explosion.

L4d my bodyguard MY BODYGUARD (15G)
Protect any Survivor from an attacking Infected 50 times.

L4d 101 cremations 101 CREMATIONS (20G)
Set 101 Infected on fire.

L4d spinal tap SPINAL TAP (10G)
Kill an Infected with a single blow from behind.

L4d zombie genocidest ZOMBIE GENOCIDEST (20G)
Kill 53,595 Infected.

L4d red mist RED MIST (20G)
Kill 1000 Infected with a mounted machine gun.

L4d achievement 5359 infected garage THE LITTLEST GENOCIDE (25G)
Kill 5,359 Infected in the Crash Course campaign.

Left 4 Dead 2

Burning sensation BURNING SENSATION (15G)
Ignite 50 Common Infected with incendiary ammo.

Head honcho HEAD HONCHO (15G)
Decapitate 200 Infected with a melee weapon.

Club dead CLUB DEAD (15G)
Use every melee weapon to kill Common Infected.

Chain of command CHAIN OF COMMAND (15G)
Kill 100 Common Infected with the chainsaw.

Dismemberment plan DISMEMBERMENT PLAN (20G)
Kill 15 Infected with a single grenade launcher blast.

Til-it-goes-click TIL IT GOES CLICK (20G)
Using the M60, kill 25 infected without letting go of the trigger.

Fore FORE! (25G)
Knock off the heads of 18 infected with the golf club.


  • It should be noted that the Common Infected bear a resemblance to the "zombies" in the movie 28 Days Later, as they are not the undead monsters of traditional zombie culture but living people Infected with a rabies-like virus.
  • Some Common Infected in Left 4 Dead 2 seems to be a bit rotten in the face as if they are really dead and are decaying. It is possible that this is another level of the infection (aside from the Special Infected).
  • Children and animals have yet to be seen in the ranks of the Infected. The most likely reason is that if children and animals were in the game, that would mean the player can kill children and animals, which would raise ethical concerns and cause huge controversy. In-game speculation include that it is possible that the Infection is too strong for children and animals, so they die instead of turning into Infected, although birds can be heard in Death Toll, Blood Harvest, and The Sacrifice, crickets can be heard during Dark Carnival, and the barking of dogs can be heard at the beginning of the trailer for Left 4 Dead 2. And in some campaigns, birds can be seen flying (However, Rochelle claims that the virus is spread through mammals, just like rabies, so birds would not be affected). It may also be that there are various animals that are akin to the Survivors in terms of having an immunity to or simply carry the virus which could explain the reason for the cows in Swamp Fever being burnt. Other possible explanations could be the Infected have either killed most of them. However, in Blood Harvest, Dark Carnival, and Swamp Fever dead cows can be seen with the skin removed around their face, indicating a rabies test. The lack of the bodies of children could also be that any Survivors saw it appropriate to take the time and give children an appropriate burial, or that they are just removed from sight to not demoralize people. A more brash or radical explanation would be that the Infected cannibalize one another or dead corpses which would remove any corpses from sight. There is numerous evidence to the contrary in-game, however, such as piles of untouched corpses throughout The Parish Campaign.
  • Sometimes, a glitch occurs where Infected are standing stationary with their arms parallel at 90º (reference position, also called the "T-Pose"), these Infected can be killed but ragdoll physics do not take effect. Also these glitched Infected can stop Survivors from moving and so it has been seen that Survivors can be trapped by these glitched Infected. To combat this you must restart the server upon which you are playing, or use explosive measures to get past them.
    • A second glitch can occur when one tosses a Pipe Bomb, such as throwing one towards a horde, and occasionally some Infected may stop moving and glide back and forth, but you are still capable of killing them.
    • In Left 4 Dead 2, sometimes it's possible for the Infected to glitch while trying to climb a pole (either a lamp post or one of the poles in Dark Carnival). The Infected would become completely still and slowly inch up the pole. They will return to normal once they reach the top, or are shot and killed.
  • Sometimes, Common Infected can get stuck in objects, such as tables or forklifts, and become invulnerable to melee attacks and must be shot to be killed.
  • Found in the sound files are clips titled to be belonging to a sort of Infected dog. This could possibly have been a scrapped feature or plans for a future addition. During the 4th chapter of Blood Harvest, it should be noted that howling can be heard in the background, most likely produced from these sound files. However, there is a strong possibility that the file could have simply been applied to the various ambience that can be heard throughout the campaigns made by idle Infected.
    • The Hunter uses the "attack" sounds for attacking with his claws while un-crouched.
  • The voices and sounds of many of the Common Infected and some of the Special Infected (the Smoker, the Boomer and the Hunter) were performed by vocalist Mike Patton who also did the voice of GLaDOS' Anger Core in Portal; (in fact, some Common Infected voices are simply reused from the Anger Core) additional voices were voiced by Fred Tatasciore and Dee Bradley Baker.
  • When the Infected are summoned in the finales you hear a scream from them. That sound is a mix of two sounds that can be found in the Half-Life sound folder called "the_horror1" and "the_horror2".
  • Whenever Common Infected are burned in Left 4 Dead 2 (excluding CEDA Worker Infected), their bodies gain a new texture effect to make them looked charred.
  • In Left 4 Dead, the Common Infected's pupils are hard to see. In Left 4 Dead 2, they seem to have developed reflective areas in the rear portions of the eyes, which glow when you shine the flashlight on them, such as in canines or felines, known as tapetum lucidum.
  • One of the symptoms right before turning into a Common Infected is possibly getting cold, as the helicopter pilot states he is getting really cold before the events of Crash Course, in which he turns into an Infected. This could be caused by the thinning of the victim's blood, which is probably why the Infected and dead bodies have faded skin colors.
  • There is an unused gore effect featuring a gigantic slash completely down the Common Infected's spine. It is possible that this would've been used should the axe had kept its overhead downwards slash and was used on a Common Infected's back. (The animation for fire axe swinging downwards still exists in the viewmodel's animations.)
  • In the new Left 4 Dead 2 DLC, The Passing, the Common Infected gain two new models. Models for the Midnight Riders fans and models for "formal"-looking Infected at the wedding.
  • Sometimes, Common Infected will attack the ending safe room door even when the Survivors are right next to it. This occurs mostly when three out of all the Survivors are outside the saferoom and the fourth is hiding somewhere like behind the warehouse shelves in the end of No Mercy's Apartments. This is also possible with Special Infected, but only if the saferoom door is inside the room.
  • In Left 4 Dead 2, a Common Infected would usually die when its head is exploded by a gun like a shotgun or a Magnum. However, on extremely rare cases, it will remain alive without its head and will continue attacking the Survivor headless (more common in the Mutation "Headshot!" as the Commons only die from headshots, decapitations, burning or explosions). This is most likely unintended, however, as a headshot is supposed to be fatal. This most likely is a hit recognition issue.
  • However there are sound effects that resemble bloody gurgling sounds which are unique to headless Infected.
  • There are no obese Common Infected. This could possibly be from the Infection speeding up their metabolism or heart rate, thus burning up all the body fat. Or possibly that they become Boomers if they are at a certain size or body shape.
  • It is possible to kill a Common Infected just by jumping off a higher ledge and landing on its head.
    • You can also kill a Common Infected by standing on them somehow. For example, it is possible to run over a Common Infected lying down and kill them without the Survivor or Common Infected realizing, though this is hard to do due to the fact the Infected are often alerted of your presence before you can get that close. A good way to do this though is to turn your flashlight off, and go in a small height distance from you and the target and jump on them.
    • Sometimes by standing over ladders, one can ensure no Common Infected can emerge from there. For example, in the car impound lot where all the alarmed cars are in The Parish. If one stands over the manhole while the horde is alerted, any Common Infected coming from the sewers will be stopped by the Survivor up top. Once they hit the Survivor, they will either die as if being shot or fall back down into the sewers to try and climb up again.
    • With a carefully timed jump and a teammate covered in bile, one can run across the heads of the Infected and use them like a bridge. However you can only do this for a short while, since you start to slowly fall after about two steps, and will collide with another Common Infected eventually.
  • Originally when in Versus mode the player was able to take control of a Common Infected while waiting to respawn after being killed as a Special Infected. This was scrapped as it was deemed too difficult for many players to attack the Survivors as they were always competing against AI-controlled Infected.
  • Many finales, such as the No Mercy campaign, do not have a clear reason as to why the Infected come. There is nothing that makes a noise to attract the Infected. It is possible that they can detect radio frequencies, and are attracted to the voices of the Survivors. As to how they get there, they probably follow the frequency to the source, and they attack whoever is unlucky enough to be there at the time. This would be backed up due to Internet not working as well as mobile phones.
    • It has also been suggested by the helicopter pilot that it's like they can sense hope, much like animals can "smell" fear. It's unlikely that he was being entirely serious, though.
  • In the Left 4 Dead 2 port of No Mercy, only the hospital patients from the first game appear among the horde of Common Infected (sadly and for unknown reasons, no surgeons or nurses do) though with far less frequency and lack of new gore effects but with the better shadows. Unlike their behaviors in Left 4 Dead, their limbs cannot be severed and their heads can be blown off with any weapon (again, also lacking the new effects). And unlike Left 4 Dead 2, knocking its head off will not produce a severed head in contrast to Left 4 Dead 2's Common Infected. However cutting its head off with slashing weapons like the Katana will make a severed head appear, but needs luck as the patient didn't get any new effects.
    • The original Common Infected's models and textures exist in the game files for left4dead2 (Male: Suits, Regular, Police, National Military Guard and Worker including head textures. Female: Casual and suit including head textures), left4dead2_dlc2 (Only Male: New version of the Hospital Patient and original unchanged version of the Surgeon) and in left4dead2_dlc3 (Male: Baggage Handler, Pilot, Rural and TSA Agent body textures including models. Female: Hospital Nurse body textures including all the Female Common Infected models), however they are only used as ragdolls because they use a lot more memory, have messy colors on their shirts (due to $blendtintbybasealpha and the new Infected variation system), square shadows and lack the other features the new Infected possess (better gore effects, gradients and so on). The "Infected Suit guy" still appears in the population.txt under "test_common_male_suit", but again, lacks the features.
  • There is a glitch when you shoot off the Infected's arms off, and it is still living, it will attack you and deal damage, though it has no arms to attack you with. However, this is highly unlikely due to their relatively low health.
  • Sometimes when facing Common Infected, when they notice you they may freeze in their ready to attack position. This is because they have accidently "noclipped" onto something (like fencing) and cannot move unless they are shoved. They still can, however, attack you if you get too close to them.
  • A very rare glitch occurs where Common Infected (and their Uncommon variants) may get shoved and get back up, only to get shoved again, even if the Survivors do not shove them. This only works with two or more, as when one is shoved, others nearby will also get shoved back from the main Infected being shoved. Once they get out of this however, they will attack the nearby Survivors.



  1. Infected:

External Links

The Infected
Introduced in Left 4 Dead Introduced in Left 4 Dead 2
Boomer nav Hunter nav Smoker nav Tank nav Charger nav Jockey nav Spitter nav
The Boomer The Hunter The Smoker The Tank The Charger The Jockey The Spitter
Introduced in Left 4 Dead Introduced in Left 4 Dead 2 Cut Infected
Witch nav Common nav Uncommon Infected nav 70px-Screamer nav
The Witch Common Infected Uncommon Infected The Screamer

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