The infected are humans who have been infected by the Cordyceps brain infection and subsequently mutated into horrific new forms. The resulting creatures are aggressive, and will attack any uninfected human and animals on sight.
The infected are the result of a sudden outbreak of a mutant Cordyceps fungus that now affects human beings as opposed to insects. The fungus reportedly originated in South American crops; various newspapers in Austin in 2013 support this claim. The fungus infects the human brain, growing mycelium inside the brain tissue and killing the brain's cells. This erases their memories and drives them insane, modifying their instincts to seek no goal other than spreading the spores to others. Eventually the fungus kills its host, and will then grow out of the host's body to spread spores.
Public reaction to the infected has been catastrophic. As the vicious fungus has taken hold of the majority of the population, the worldwide pandemic causes the total breakdown and destruction of society through widespread violence; the failure of martial law to contain the outbreak, the military's increasingly violent efforts to censor information, and the near-extinction of humankind. The Fireflies – a militia group formed in response to military oppression – have conducted a mostly futile war against the barely-functional government. They believe they can create a vaccine through study of the fungus and its hosts, one of the last organizations to do so.
Those who are clear of infection are ordered by martial law to reside within a quarantine zone. The military at one point bombed areas outside the quarantine zones to kill the infected and execute anyone suspected of infection on sight.
[...] the antigenic titers of the patient's Cordyceps remain high in both the serum and the cerebrospinal fluid. Blood cultures taken from the patient rapidly grow Cordyceps in fungal-media in the lab...
For humans that have been exposed to a mutated strain of Ophiocordyceps Unilateralis, the fungus attacks the brain and begins to alter the behavior of its host. The host will then go through four different stages of infection: runner, stalker, clicker, and bloater or shambler; each stage is more dangerous than the last. However some have had resistance to the infection, notably Ellie; she hasn't turned despite being infected for over five years. There is also the unique rat king stage.
The infection also spreads directly through contact with an infected or via their corpse - that is, the infectious spores created by the Cordyceps and released from the host's body upon death. These spores can quickly infect an individual, making breathing difficult and movement sluggish within only minutes is exposure in such spore dense areas. Only Ellie has exhibited the ability to breathe spores without difficulty.
The infection is also transmittable through an infected biting another individual. The infection will then spread through the new host's body, gradually turning them into a runner over a period of two days. The infection will also turn the bit area red and black and cause the host to sweat profusely and become disoriented. It can also cause their eyes to sting and make it difficult for them to write. However, infected hosts who resist the infection, like Ellie, are unable to pass on the infection when biting other individuals.
Spore development is the last stage in the life cycle of the infected. This lifeless carcass serves as a breeding ground for the fungus to spread throughout the environment. When near death, an Infected will find dark, moist corners to die in. While this may be the end for the host, the fungus continues to grow. Those living in the quarantine zones are relatively safe because they are in places with significant airflow, leading to a low spore concentration, explaining why the only places with significant spore toxicity tend to be underground or abandoned buildings.
In order for the fungus to infect a host body, the host must first be alive. Dead victims who come into contact with the infection do not undergo transformation. According to the Center for Disease Control, the victim can only become infected by inhaling the spores directly or coming into contact with an infected's bodily fluids, usually from a bite.
Infected individuals must be exposed to specific conditions and circumstances in order to progress to the next stage of infection, otherwise, they may stay at one stage for an extended period of time. This is presented in the large number of runners in Lincoln and Jackson.
Due to growing a fungus within themselves, all of the infected are vulnerable to fire. However, the rat king stage is immense in spores that it can survive extensive exposure to fire, able to charge through flames with only minor stagnation.
The infected humans have since undergone a strange mutation by a specialized strain of Cordyceps. runners seemingly begin to experience hair loss, discolored skin accompanied with lesions, and bloodshot eyes. Stalkers can be seen with significant fungal growth around their eyes and shoulders. Clickers are horrifically mutated by the infection. By this stage, the skull has been split open due to advanced fungal growth on the brain, growing over or outright destroying the host's eyes. Their teeth are rotten and jagged, and their skin is covered in mold. The fungal growth on bloaters is so advanced that it begins to form armored plates on the host, while also causing the body to bloat significantly. The fungus also seems to offer the host some protection against the elements, such as the cold. When the host is killed or dies from advanced fungal growth, the fungus continues to grow throughout the body, eventually emitting spores.
Upon becoming infected, the victims gradually lose any ability to think freely and begin to behave irrationally as the fungus spreads in the brain. Relying on warped instincts, the infected will attempt to attack and/or eat any human they find. This becomes most prominent at stages 3 and 4, when their human characteristics begin to cease to exist entirely (e.g. feelings, thoughts, etc.). They lapse into their primitive, animalistic instincts, attacking anyone or anything that disturbs them, almost as a way to protect their territory. However, clickers can be seen twitching and sometimes clawing at the fungal growth covering their face, suggesting that there still may be vestigial elements of the host attempting to resist the infection. According to Jerry Anderson, fungal-growth in the limbic regions normally accompanies the prodrome of aggression in infected patients.
The fungus spreads to the host's eyes as it grows, covering and blinding them. They then develop a primitive form of echolocation to locate prey, which results in them making a distinctive clicking sound. After some time, the fungus kills the damaged host, usually in a closed-off space so the fungus can spread further.
The infected, while having a higher pain tolerance than ordinary humans, are still susceptible to conventional injuries. A runner, when not attacking survivors, will moan in pain due to the fungal growth deforming its body and clickers will struggle while being shivved. Sometimes infected that still have their entire face intact look sad or worried as they attack, indicating that first and second stage infected are aware of what they are doing, but cannot control themselves. Gunshots are capable of startling runners and stalkers, so they seemingly feel fear in the early stages of infection. All stages of infected will flail and scream wildly when set on fire or severely wounded. The body of an infected will spasm violently when the host is killed. The infected have also developed sensitive hearing, as they can hear sounds that normal survivors cannot, such as the player hurdling nearby obstacles.
Stages of infection
|Runner||Runners are people who recently turned into infected. They are defined by their intense speed, sluggish attacks, and tendency to attack people in hordes.|
|Stalker||Stalkers are people who have been infected from somewhere between two weeks to a year. Per their name, they stalk and hide from prey in the dark and attack at opportune moments. Some also latch onto walls and allow the Cordyceps to fester, keeping the host alive until prey walks by, at which point the stalker breaks free and attacks.|
|Clicker||Clickers are people who have been infected for at least one year. The long time elapse has allowed the fungus to spread all over their bodies, blinding them and forcing them to use echolocation to find prey. However, the fungus has granted them enhanced strength, making them fearsome foes in close-quarters combat.|
|Bloater||Bloaters have been infected for several years. The fungus has led them to become slow and blind, yet incredibly strong and resilient with the fungal growth serving as armor plating. bloaters can also tear fungus from their bodies to use as spore bombs and throw them at their enemies. However, this additional fungal growth makes them vulnerable to fire.|
|Shambler||Shamblers are people who have been infected for several years and typically inhabit areas thriving with water. While not as physically enhanced as clickers or bloaters, shamblers are able to grapple prey and expel large spore clouds from their bodies, which cause acidic burns on the skin of prey. When killed, the spores explode, releasing a final burst of Cordyceps into the air.|
|Rat king||The rat king is a unique stage of infected that developed in the Seattle hospital after over twenty years of infection. Formed from several infected combining into one, the rat king is colossal in strength and size, and able to take extensive damage from fire, bombs, and guns. Even after taking much damage, it does not die, but instead, its various infected parts will start to break off from the larger mass and attack along with it.|
Death and corpse
Even after an infected individual has died, the fungus will continue to grow; consuming the body's mass to form a fruiting body and releasing spores that infect any human that breathes them. Survivors use gas masks to prevent this.
The process of forming the fruiting body causes the corpse to become skeletal and brittle, fusing the remains to surfaces as it continues to grow. As sufficient time passes, the fruiting body becomes a "moss" that can fill entire structures with deadly fungal growths the color of pasty human flesh. Both of the spores and the fruiting body die quickly when exposed to sunlight, limiting the danger they present.
The Last of Us
- Interestingly, in-game clickers jog when chasing Joel or an AI. However, in the cinematics I need a car and Name's David, clickers do sprint.
- Clickers also sprinted in the PGW trailer for The Last of Us Part II as well.
- Clickers can be observed clawing and scratching the fungal growth on their eyes as if trying to get rid of their blindness.
- In Dontnod Entertainment's video game , the protagonist Sean Diaz jokingly makes clicker noises to try to scare his brother Daniel, after pointing out that a mushroom tree looks like a clicker.
- In Hypixel, one of the most popular Minecraft multiplayer server, there is a game known as "Infection" where an infected player has a pixelated skin almost resembling the clicker.
- In Techland's video game Dying Light, there is an Easter egg in which a zombie with its head shaped like a clicker comes out of an elevator. In addition, it will drop an item called "Clicker" when killed.
- In the cartoon The Amazing World of Gumball, the episode "The Parasite" features a clicker when Gumball merges with Darwin in order to warn Anais. He also mentions that he takes the zombie's form from a video game.
- The infected appear to rest standing up. They do not click or attack even when the player is directly in front of them, unless provoked, while resting.
- If the bloaters in the Pittsburgh hotel basement and UEC dormitory kill Joel, they will actually knock the mask off of his face in a special death animation.
- When controlling Ellie, the bloater death scene changes; the bloater simply punches Ellie, killing her with its sheer strength.
- In-game materials, concept art, and the "Grounded" Making Of documentary all show that the fungus is able to rip through bone.
- The skin of clickers visibly "chalks," or forms large patches of scale-like tissue that glow in the dark. The patches are seemingly an earlier stage of the fungal infection growing out of their hosts' bodies, before said growth engulfs the entire body as seen with the final bloater stage of infection.
- runners do not moan as much nor in the same way as in previous beta demos as if in horrific pain but remain silent for the most part. However, they will screech when startled.
- Despite clickers using echolocation, their echolocation is very crude compared to creatures like bats, as they will not notice that something is alive or moving unless it is directly in front of them. This supports the assumption of the front being where the clicks are sounded, as their face plates are shaped like a , directing it straight ahead of them, but not all around.
- Clickers do not click the same way as in previous beta demos where it would sound more like constant tapping of the tongue. In the final game clickers click by waves of croaking rather than constant tapping.
- Stalkers appear the least amount of times when compared with other types of infected, with the player encountering them a mere three times in the entire franchise so far, twice in The Last of Us, and once in the Left Behind DLC.
- They will appear more frequently in Part II, in the form of "mini-boss battles". This is possibly because a stalker's echolocation works best in enclosed areas.
- Even though objects can be thrown to distract the infected, it should be noted that a major drawback to doing so is that it will draw them out of their scripted paths and allow them to freely roam the area, making it more difficult to predict their positions. If necessary, it is advised to have a steady flow of items to throw to keep them in the same area.
- Some of the concept art in The Art of The Last of Us shows runners wielding tools such as shovels, knives, and rakes as weapons.
- Early concept art for the infected showed them with an almost alien appearance, with insect like claws and glowing eyes, but the developers choose to maintain a human resemblance so it would make them feel more unnerving.
- Unlike with hostile humans, flashlights do not alert the infected to Joel's or Ellie's presence, although when shining the light in their eyes, they do appear to react to it by holding up their hands to shield said eyes. This could be due to their low intelligence, as it seemingly suggests that the infected are too simple-minded to distinguish flashlights from any other ambient light sources they encounter.
- A clicker appears near the end of PlayStation's Greatness Awaits trailer.
- In the University Laboratory, an X-ray of an infected (possibly a stalker) displays the fungal growth on the head.
- As was revealed by Naughty Dog at PAX Prime Panel 2013 Event, there were originally supposed to be other infected animals, including elephants, which are described as having fungal growths on their legs and mushrooms in their heads. However this design did not make it into the final game, therefore, it is unknown if in-universe animals are capable of becoming infected, as they often seem to be scared away by infected. It's shown during "The University" chapter that monkeys can be infected, though they appear to be asymptomatic, simply being carriers rather than true infected.
- Joel can punch a clicker to kill them when the clicker grabs an AI partner, such as Bill, or when they are stunned by a brick or bottle.
- Bloaters are the only stage of infected that do not appear in Left Behind.
- The infected's skeletal system appears to be much weaker than a normal human, as Joel can stomp on a runner's head or smash them against a wall and completely destroy their head.
- In an interview with Neil Druckmann on The Last of Us Part II, it is hinted that the environment itself plays a role in the various states of the infected's lives. When discussing the shambler, it was stated that the team didn't throw in a new enemy type just for the sake of it, they carefully thought out how it fits into the lore of the world of The Last of Us; Druckmann is quoted as saying "In the first game, there is all this documentation about the different stages [of the infection], now we have to justify why there are different stages. Why are there mutations of these things? Without getting into it here, there is something about the environment and how much time has passed that has allowed these mutations to occur."
- The rat king can kill Abby either by corroding her skin with mycotoxin and snapping her neck or violently ripping off her limbs.
- It may also be possible that the rat king absorbed a significant amount of steroids and other drugs, due to its prolonged time in the flooded hospital.
- What Are You Scared Of?
- Infected infographic
- "The Quarantine Zone"
- Twenty Years Later
- Evacuation leaflet
- Surgeon's recorder
- "The Farm"
- "Seattle Day 2"
- "Seattle Day 2"
- "The Outskirts"
- The Last of Us: Left Behind
- I'm not infected
- Bank robber letter
- Patient's note
- "Seattle Day 3"
- "The University"
- Medical pamphlet
- "Bill's Town"
- "Bus Depot"
- "Lakeside Resort"
- TLOU Part II Demo
- Druckmann interviewed for PlayStation 2019 blog