- "They might still look like people, but that person is not in there anymore."
- ―Ellie to Sam
The Infected are mutated humans, reshaped into horrific new forms by a recombinant fungal infection. The resulting creatures are highly aggressive, and will attack any uninfected human on sight. The Infected are the main antagonists of The Last of Us.
The fungus reportedly originated in South American crops; various newspapers in the prologue 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 will kill it's host, and will then grow out of the host's head to spread spores.
Public reaction to the Infected has been catastrophic. As the vicious fungus has taken hold of the majority of the population, spreading havoc and panic far and wide, 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 mankind. The Fireflies–a militia group formed in response to military oppression–have conducted a mostly futile war against the dysfunctional government. The group is one of the few remaining organizations that believe they can create a vaccine through study of the fungus and its hosts.
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 withhold the infected and executes 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..."
- ―Surgeon's recording
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; each stage is more dangerous than the last.
The infection is also spread 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. 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 an Infected feels it is close to death, it will find dark, moist corner to die in. While this may be the end of the line for the host, the fungus will live on. The Last of Us game team has stated that the people in the quarantine zones are relatively safe because in places with significant airflow, the spore concentration cannot build up, which is 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.
Physical appearance Edit
As said in the previous section, the Infected humans have since undergone a strange mutation by a specialized strain of cordyceps. Over time, growths protrude out of the orifices of the human hosts and it changes their physical appearance. Their teeth are horribly rotten and jagged. The fungus on Clickers and Bloaters is bio-luminescent. At later stages, their body begins to bulge, and more fungi growths can be seen on their skin. When the host is killed or dies from advanced fungal growth the fungus continues to grow throughout the body; emitting spores.
- "You know, as bad as those things are, at least they're predictable. It's the normal people that scare me."
Upon becoming Infected, the victims eventually lose any ability to think and begin to behave irrationally as the fungus spreads in the brain. Relying on warped instincts, the Infected will attempt to throttle any human they find.
As the fungus grows, it gradually makes the host blind. 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 will kill the host if too damaged, 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. Clickers will occasionally struggle while being shivved. Sometimes infected that still have their entire faces intact look sad or worried as they attack. This may indicate that first and second stage infected are aware of what they are doing, but cannot control themselves. Gunshots are capable of startling an infected individual, so it is likely they feel fear in the early stages of infection. However, since their humanity is completely destroyed by stage three, most humanistic characteristics cease entirely (e.g. feelings, thoughts, etc.).
Stages of infection Edit
Runners are the first and weakest stage of the Infected who have recently entered their transformation. Since the eyes are first targeted by the fungus, runners have poor eyesight, but maintain many human instincts. For example, their moans are still human, just like their overall appearance. A way to tell them apart from normal survivors is their glowing red eyes. Their body language is sluggish while they are passive, suggesting they are resisting the fungus's influence. Sometimes they do not attack at all, even when non-infected individuals are right in front of them. These non-aggressive runners will only attack if attacked first or when an object is thrown at or near them, thus losing control. Much like sneezing, the urge to attack after such interactions happens involuntarily and unwillingly by the host. Runners are confirmed to be able to attack in packs flailing their arms trying to trample the survivor. 
Runners seem to have an easier time than humans when it comes to spotting Joel and Ellie, since, with humans, Joel can just walk behind them and strangle them, something that is not possible with Runners without them spotting Joel. Also, moving Runners seem to be capable of spotting Joel when crouch-walking.
Stalkers are the second stage of the Infected. They have the vision and speed of Runners. They are hybrids of Clickers and Runners. The most notable physical traits that define the "Stalkers" is the distinct croaking noises they make, the beginning of fungal growths on the head and face, the development of pseudo echolocation, and their discretion when chasing a victim - they will strafe and take cover, eventually closing in on the victim, hence the name "stalker". Stage 2 may take place anywhere between a few days after the start of the infection (Stage 1) and up to a year (Stage 3).
Their strength is equal to a fit human being as their attacks can interrupt actions made by the player.
Stalkers are the fastest of the infected to notice survivors, surpassing even the early-stage Runners in awareness.
According to the Stages of Infection collectible found in The Last of Us demo released with God of War: Ascension, the modus operandi of a stalker is to "hide and ambush victims." The collectible implores readers to check their surroundings, but no other information is provided.
They can be shivved and strangled like Runners. There is a tag worth 100 in-game currency called 'The Hunter Becomes the Hunted' for stealth killing a Stalker from behind for the first time.
Stalkers are rare in the entire game and are only encountered in some scenarios. Their "clicking" may however be heard in the distance in various other areas, but it only serves as ambiance. Depending on the location, they can be quite common in areas like the basement of Grand Hotel in Pittsburgh.
Some Stalkers have a bioluminescent vein in the face, and some of them are known to be impossible to punch, forcing the player to shoot them or use a melee weapon.
Clickers are the third and most distinctly recognized stage of the Infected. They have had prolonged exposure to the fungus, and now possess strength that significantly surpasses the average human. This makes them deadlier, but at the price of being completely blind due to fungal infection overtaking their face. However, Clickers are able to maneuver through areas by utilizing echolocation, which produces noticeable clicking noises to locate sources of sound.
Clickers appear less human than Runners, with faces that are skewed and scarred by fungus developed from their infected brains. Clickers are dangerous and much more aggressive than Runners, and no longer resist the fungus because their humanity has been eliminated. Interestingly, most of the Clickers seen in the game appear to have been female humans.
When provoked, a Clicker will immediately enter into a "berserk mode," aggressively flailing its arms. At this point, if a survivor has been "spotted" by a Clicker, the Clicker will attack head on and will not flinch when shot unless using high powered rounds. If the player is grappled by a Clicker, he can save his life if they have a Shiv and at least level 1 of the Shiv Master skill. If not, Clickers will bite and rip into Joel's neck, instantly killing the player. It is possible to avoid or distract Clickers instead of fighting them directly by using bottles or bricks. Boxing a Clicker with bare hands is ineffective — after three punches, Joel will not have time to back away and will be instantly grappled by the Clicker if it was not killed. Most of the time the Clicker's berserk mode will override his punch. It is recommended players use a melee weapon if they choose this form of attack.
Clickers can be stealthily killed by either using a shiv or the bow and arrow. Still, using an arrow to kill a Clicker requires the player to achieve a headshot; this has 80% of chances of breaking the arrow.
It is fairly easy to outrun a Clicker, as their crude echolocation has a short range and they only walk quickly to their destination. When far enough or behind cover, the Clicker will get confused and click in all directions. In the launch trailer for the game shown at the 2011 Spike Video Game Awards, Clickers had the ability to run as fast as Runners. This ability was removed from the final game.
Bloaters are the fourth, final, and most dangerous stage of the Infected and are immensely strong. Bloaters take the longest to develop, making them the rarest of the infected. They are covered in thick fungus that effectively doubles as plate armor. Due to this protective covering, they can withstand multiple hits from weapons such as the Shotgun and Hunting Rifle, and even hatchets and machetes making them extremely tough to eliminate. Bloaters are extremely aggressive, but are rather slow-moving causing them to be more predictable than other infected. Like Clickers, Bloaters 'see' using echolocation to locate and trap a survivor as the fungus has completely deformed their face and blinded them, though their echolocation is a lot less refined than the Clickers. If a Bloater grabs a survivor, it will forcefully rip their jaw apart through brute strength. There is no way to defend yourself if grabbed - the result is an instant kill. Bloaters will throw balls of spores from their own body as a weapon, which disperse into a spore cloud on impact. These will eventually damage the health of anyone in the immediate area, even if they are wearing a gas mask. Their spores are not shown to be effectively infectious.
Bloaters, like all Infected, have a weakness to fire. When set ablaze a Bloater will wildly thrash around trying to put out the flames. After being immolated, they will be charred black and smoking. Their armor will also be charred and brittle, making them vulnerable to low-powered weapons. Despite this weakness, fire-based weapons such as Flamethrowers or Molotov cocktails still require multiple uses before killing a bloater. Their other less effective weakness if fire is inaccessible is armor piercing rounds from an upgraded weapon like the hunting rifle. It will take fewer shots to kill if the weapon has the Power and Armor-piercing upgrade.
Bloaters are found in the five following locations:
- 1 in the gym of the High School in Lincoln. (Must be fought)
- 1 in the basement of the Hotel Grand in Pittsburgh (not there on easy mode). (Can be avoided)
- 1 in the dormitories in the UEC. (Can be avoided)
- 1 in the mill during winter. (Must be fought)
- 3 in the underground tunnel in Salt Lake City. (All can be avoided)
- The most efficient way to kill bloaters is to throw a Molotov Cocktail or use the Flamethrower on them. Then, while they are stunned, use a shotgun and shoot two or three shots to kill the bloater, saving supplies and ammo.
- Another very efficient way shown in "TheMediaCows" walkthrough of the game to kill bloaters is, to throw a Molotov Cocktail then use a bomb while they are on fire.
- When dealing with A Runner, Stalker, or Clicker, and the player has access to a brick or empty bottle and a blunt weapon, the player can stun the Infected by throwing the brick or empty bottle to it then running towards the Infected while swinging a melee weapon. This will result in an instant kill.
- The El Diablo is effective against a bloater because it only takes 2 shots to kill one.
Death and CorpseEdit
Even after an Infected dies, the fungus continues to grow. By this point, the Infected's body becomes skeletal and brittle, and the fungus sticks the body to whatever surface it is on, including doors, and walls, making entryways hard to reach. The only way to remove the cadavers is to rip them out of their rooted area. The only danger these immobile infected possess is the spores that are being expelled from the body and will infect anyone that breathes them.
- It seems the Infected rest standing up. They do not click or attack even when you are in front of them unless provoked while resting.
- From the concept art it is quite clear that the fungus is able to rip through bone.
- In-game, Clickers seem to rapidly walk while aggressively swinging arms, but during the cutscene when Joel and Ellie get into a safe place with Bill, you can see a Clicker that runs towards them without swinging its arms.
- Runners don't moan as much nor 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 where they will not notice that something is alive or moving unless it is directly in front of them. This supports the theory of being where the clicks come out, as it is shaped like a megaphone, 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.
- Even though objects can be thrown to distract Infected, it is not advised unless absolutely necessary as doing so will alter their scripted paths and allow them to travel to all areas of the map, making their behavior more unpredictable, making the chances of death higher. If necessary, it is advised to have a steady flow of items to throw to keep them searching in a specific area and not scatter everywhere.
- Some of the concept art in The Art of The Last of Us shows Runners wielding tools such as shovels and rakes. This indicates that at one point in development, humans in the early stages of infection would possess enough of an intelligence to use tools as weapons against Joel. As this concept was not used in the actual game, there is no way of telling if the in-universe Runners and Stalkers were still capable of such actions.
- 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.
- The Infected do not react to having your flashlight on. This may be due to the similar fact that fungi have no phototropism (reaction to light source, "heliotropism" is the reaction to the sunlight), or the hosts' senses to light seems to be impaired or the retina has been overgrown by the fungus.
- Seeing as how the concept art shows a hole in the middle of the Clicker's heads, this may mean that the eyes of the former human could come out of it in an unknown 5th stage of the infection. However, that is very unlikely, so it may also be a sort of mouth where the clicks come out (some in-game Clickers do not have this hole) or an ear that hears the clicks. It could also be to launch possibly infectious spores, like a cannon.
- A Clicker appears near the end of PlayStation's Greatness Awaits trailer.
- In the University Laboratory there is an X-ray of an an Infected (possibly a Stalker) that shows that the fungal growth on the head is actually the infected brain simply growing out.
- Initially there were supposed to be other animals that were infected, specifically elephants. Infected elephants are described as having fungus growing out of its legs and mushrooms in its head. However this design did not make it into the final result. It was revealed by Naughty Dog at PAX Prime Panel 2013 Event.
- It is possible to hit or kill a Clicker with Joel's punch. If the Clicker is grabbing an A.I. partner, (such as Bill) you can run up to them and punch them.
Concept art Edit
- ↑ http://www.shacknews.com/article/77676/the-stages-of-infection-in-the-last-of-us
- ↑ http://m.youtube.com/#/watch?v=00y3QRovboA
- ↑ http://www.youtube.com/watch?v=HA2cuwYSIqs
- ↑ Demo. The Last Of Us. May 31, 2013.