Infected

This article is about the group from the HBO series. For their appearance in the video game series, see Infected. For the second episode of the series, see Infected (episode).

Infected
History
Other names	Demons (by Seraphites)
Group type	Infected
Location(s)	Worldwide
Key figures
Stages	Runner Stalker Clicker Bloater
Connections
Enemies	Survivors
Behind the scenes
Appears in	HBO's The Last of Us

“

They're connected, more than you know. The fungus also grows underground, long fibers, like wires, some stretching over a mile. You step on a patch of Cordyceps in one place and you can wake a dozen infected from somewhere else. ―Tess regarding the infected.

”

The infected are humans who have been infected by the Cordyceps brain infection and subsequently mutated into horrific new forms in HBO's The Last of Us. The resulting creatures are aggressive and will attack any uninfected human on sight.

Overview

In 2003, a subspecies of Cordyceps or Ophiocordyceps, a parasitic fungus known to only infect insects such as ants and caterpillars, was able to rapidly evolve due to Earth's temperature increasing. Initially unable to infect humans due to their higher body temperatures, this new strain of evolved Cordyceps was resistant to such temperatures and thus was able to use humans as hosts. As such, in the summer of 2003, the Cordyceps brain infection outbreak occurred. Starting in Jakarta, Indonesia, the infection rapidly spread to the United States and the rest of the world, causing a complete breakdown of global civilization. The fungus infected humans primarily through yeast-derived products like flour and food created from it, like cookies and bread.

Biology

Infection

A recently infected boy tests positive for Cordyceps.

Infection from cordyceps relied on various methods. Initially, the cordyceps infected yeast products like flour, meaning all resulting foods containing it, like cookies, bread and pancake mix, could transmit the infection. On September 24, many food products containing this new strain of cordyceps became available for purchase in many supermarkets around the world. People unknowingly bought the products and consumed them. By Friday morning, people began to get sick, displaying numerous symptoms such as coughing, slurred speech, muscle spasms, and increased aggression. It also made a person cold while infecting them. In the early hours of Saturday morning, enough people around the world had contracted the infection and turned into runners; in Joel Miller's words, this led to a "critical mass", causing the collapse of society worldwide to the extent that "by Monday, everything was gone" and humanity was faced with an apocalyptic level event.

To counter the infection, the solution at first was simple: don't consume any flour-based food products or even make them. However, this did not stop those already infected. With no cure or vaccine in 2003, FEDRA's solution was to carpet bomb all major cities and place civilians who survived into quarantine zones to stop the spread of infection. While somewhat successful, the infected humans became transmitters of the disease by biting their victims instead. They would erratically chase any uninfected human and bite them to spread the disease. The pace it would infect someone varied depending on where someone was bitten, ranging from twenty minutes if bit in the face or neck, 2-8 hours if in the torso, arm or shoulder to around a day if bitten below the hip.

It was also possible for the infection to spread to unborn children in utero by an umbilical cord, with Anna's infection transferring into Ellie Williams within seconds of contracting a bite. However, this enabled Ellie's immune system to adapt to the infection, making her the only known person in the world with the disease in her body but completely immune to its effects. This was even true after she contracted bites from a runner, clicker and even a stalker years later in life. For everyone else in the world though, bites from infected always infected their victims and destined for them to succumb to the cordyceps control. In rare cases, some infected were able to repurpose a human's respiratory system to emit spores into the atmosphere instead of just carbon dioxide. Through this, they could spread the infection. The only known case of this was on the B2 level of Lakehill Seattle hospital. Ellie was also uniquely immune to these spores, remaining undeterred breathing in the dense air despite it overwhelming and consuming several WLF soldiers, including Nora.

A runner wandering around Alpine.

Besides looking for bite marks, humans developed new ways to detect infections. Notably, FEDRA developed scanners that could be pressed into people's necks. They would display a reading in seconds revealing if the scanned individual had cordyceps' in their body or not, showing green if clear and red if infected. Independent survivors also developed the method of keeping a close eye on anyone suspected to be infected, awaiting to see if they turned. A test to assure this was to see if the suspected infected could count from one to ten slowly, could hold out their hand without it shaking for a prolonged period of time and check if the bite mark had turned red and swelled. If the person suspected was indeed destined to succumb to the Cordyceps, then the survivors would shoot them, typically in the face.

Dogs are also capable of detecting the infection within a human even before the fungus takes control of the host. Danny and Connie Adler's dog, Mercy, was able to detect the changes occurring in Nana, and upon her turning into an infected, became frightened by her and instinctively desired to stay away from her. The Jackson community had their patrols assisted by dogs to help determine whether or not survivors entering their lands were infected; if they reacted negatively, the patrolmen would kill the survivors. Dogs could also be trained to kill the infected, with the dogs at Jackson knowing instinctively to jump on and maul the runners to death that breached the town.

Physical appearance

Detecting an infected human was evident by their physical change in appearance. While many infected still resemble humans, distinct traits revealing as infected were the addition of cordyceps and fungi growing out of their body. In the early hours after infection, many infected would have yellow eyes and emit fungi from their bodies. Indeed, if in dead individuals, these fungi would take over all the cells and arteries in their bodies, with breaking the surface of their skin revealing it had all transformed into cordyceps.

After prolonged infection, many fungi hyphae grew out of their ears and follicles in their hair to begin covering their head, sprouting out in a disfigured manner. Eventually, this would develop so much that the fungi would completely cover their heads and eyes, preventing them from seeing at all. Their teeth also rotted away, leaving only decayed gums and jagged fangs remaining, improving their ability to tear into flesh.

There were also rare cases of infected who were so far gone into the infection that their entire body was consumed in the fungi. or to avoid harsh weather conditions. They still possessed the ability to walk but their vocal cords now could only roar in deep tones. The infection was so far gone that these infected were much taller than humans as the fungal growth formed large patches of scale-like tissue. It is from these tissues that form the mycotoxin pouches and engulf their entire body.

Behavior

Once infected, the fungus eventually hijacks the host's motor functions and takes control of their body, turning them violently aggressive. Relying on warped instincts, they are compelled to attack and infect other people in order to spread the infection via tendrils that sprouted from the mouth. There were also instances where infected would attack animals, like bears and deer, even continuing to attack even after it killed other infected. When unaware or far from prey though, most infected were stationary, tending to lie down writhing on the ground or staggering around aimlessly in open spaces or condemned buildings. Some would even hide underground, whether by force, as FEDRA did in Kansas City, or to protect themselves from extreme weather conditions like snow storms.

The infected also seem to be all linked together as a hive mind due to the network of Cordyceps mycelium growing underground. Disturbing one patch of the fungus could awaken another one with a horde of infected hosts lying dormant up to one mile away. This also included if a live infected was killed, its death triggering a nearby horde to awaken and chase towards where it was killed. This connection could also grow in roots, such as in trees. While the winter could freeze these roots, heat from even a burning sparkler would be enough to restore them and allow them to grow and connect with living infected elsewhere. The strength of this hive mind could even cause a horde to end its pursuit of one group of humans and prioritized where the cordyceps had sensed there was more prey to infect. In 2029, a horde that Abby Anderson had triggered to chase her in Jackson cut off its pursuit and attacked the community in Jackson itself after the cordyceps there was disturbed, it even summoning another horde lying dormant in wait while in the mountains to attack them as well. Even the heat from flares could attract whole hordes, such as one that attacked a WLF squad in the subways of Seattle.

An infected in Boston.

When passive, many infected tend to lie down in an area and allow the fungus to emit and grow from their body. The fungus gradually attaches them to the environment around them until they eventually stick to the floor or walls, becoming a breeding ground for the Cordyceps until they eventually die. In one unique case in Lakehill Seattle hospital, the infected there remained untouched since 2003. Because of this, they gathered in the dark, poorly ventilated and enclosed space in large numbers and the fungus grew heavily around the environment. These infected stuck to the walls and uniquely began expelling a large number of spore clouds from their body's lungs. If the fungus has dried, it usually indicates that the infected hosts inside are dead. This process can take weeks or even months. According to Joel, these inert hordes of infected tend to only appear in highly populated areas like cities, with the countryside being too remote for such large hordes to form. Indeed, the isolated town of Lincoln only had the occasional wandering infected. Although, some hordes would migrate in large numbers during cold winter seasons and could hide underground in the countryside, unless disturbed by sudden violent events like avalanches.

However, not every infected remains as passive. While most do go on to die and become a permanent breeding ground, a rare few will progress even further. Because of the continued development of fungal growth throughout the body, especially around the face, the infected eventually go blind as the fungus grows over or outright destroys the host's eyes. Because of this blindness, they develop a heightened sense of echolocation, generating croaking and clicking noises to detect sounds and objects in their environment. According to Ellie, she heard stories that there is a further stage that can throw spore projectiles at its target.

The infected are sometimes able to sense whether or not someone is infected and, depending on the severity, may choose to help accelerate the process. After Tess was infected, one of the infected spotted her, but did not attack; rather, it came up to her to transfer some hyphae from his mouth to hers as if it were a kiss to help speed up the infection process. On the other hand, they would not hesitate to attack Ellie, who is infected with the fungus but immune to its effects.

By December 2028, new variants of infected have formed. Over the years, some of them grew more intelligent. For instance, Ellie encountered an infected stalker capable of hiding from her in the shadows. It would wait until it was sure Ellie was distracted before surprising her. While Ellie could still kill it by shooting it to death, this stalker variant's intelligence was notable enough that Ellie and her patrol partner Dina were called in to inform the Jackson council about it. The stalkers were not unique to Jackson either, with a whole pack of them present in Seattle as well by 2029. This rise in intelligence was also present in a horde around Jackson. The horde changed directions if one member recognised an easier path to reach their prey; all of the infected abandoned their efforts to attack one part of Jackson Hole and instead followed a bloater who breached a different section of the wall.

Variants

Runner

Those in the early stages of infection, called runners, still closely resemble humans. Visually, their eyes are bloodshot and dilated, and clusters of veins can be seen pulsating through the skin. Most notably, dozens of slender tendrils, formed from hyphae, will begin to emerge from the mouth. It is through these tendrils that they spread the infection to other humans via bites.

A runner trapped under rubble.

Sometime after their infection, even though they still somewhat resembled humans, some runners will start to develop some more advanced fungal growth. For these ones, the hyphae grow under the skin, creating noticeable bumps and grooves, and fungal plates emerge from the skin, along with an unknown green discharge. The infected's eyes and skin turn yellow at this stage. The most notable characteristic of this stage, however, is that the fungus has started to emerge from the infected's eyes in a truly disfiguring fashion.

As humans under the control of the Cordyceps fungus, these infected exhibits warped, animalistic behavior. As the fungus has hijacked their motor controls, they often display violent muscle spasms, and they will often scream and gasp heavily, especially when spotting prey. Highly aggressive and active, these infected are compelled by the fungus to attack non-infected humans. This urge removes any sense of self-preservation, and the host will sprint and leap at their target even if it leads to self-injury or death. They consequently lack fine motor control, typically overrunning their targets, and stumbling or crashing into objects or walls. Despite this, they recover quickly and will keep chasing their prey at high speeds. Their feral nature does make them predictable, making them easy to kill with traps or weapons explosions and even fire.

Clicker

A clicker in the Bostonian Museum.

A fully developed infected host over a longer period of time would become a clicker, horrifically deformed by the infection. They formed regardless of the age of the infected host, with some clickers even being children. Due to the advanced fungal growth on their brains, the skull has been split in two to allow continued growth, leaving their faces completely skewed and scarred, only leaving behind a maw of jagged teeth. The excessive fungal growth has left them blind, forcing them to develop a rudimentary and crude form of echolocation to "see" their surroundings, which has earned them the name clickers for their distinctive clicking sound. By this point, whatever clothes the host may have been wearing are mostly tattered and destroyed. Unlike the previous two stages, the clicker lacks the fungal tendrils that were originally present in the host's mouth.

Clickers have large patches of rashes all over their body as well as small fungal growths, creating large patches of scale-like tissue coming from outside their host's bodies, especially their necks and shoulders. They croak and whine when unaware, limping around their space. When they do hear noises, however, they rush towards the source of the sound. Even the smashing sounds of a bottle were enough to lure them in a certain direction. They are fast, able to sprint and leap over obstacles with enough force to knock people down—one managed to tackle both Joel and Ellie at the same time. Once they have found their target, their go-to attack is to disarm their prey and either savagely maul them to death or tear their throat out with their teeth. A clicker could even catch and maul an antler to death and six clickers were able to overpower and kill a bear, though only two survived the fight against it.

They also have enhanced strength and durability. For instance, it took several stabs from Ellie's switchblade to the neck to kill one. One could also withstand multiple gunshots to the body from Joel's assault rifle, while another still had the strength to knock Tess backward after she hacked into its armor-plated head with an axe. Despite this, they could be killed by multiple gunshots to the head, the bullets from Joel's revolver able to pierce the fungal growth and kill two infected. High powered rounds from a hunting rifle were also capable of killing them in one shot, even from a very long distance.

Given their rarity in and around quarantine zones, FEDRA schools did not teach their students about the clickers, although Ellie had heard rumors about them. According to Henry Burrell, surviving an attack from one clicker was an incredible feat for survivors to achieve, expressing his astonishment when Ellie informed him Joel saved her from two clickers in Boston. Clicker encounters were also severe enough that the Jackson patrolmen were meant to report back to the council if they found one rather than facing it themselves, though this didn't deter Ellie and Dina.

Bloater

A Bloater

Bloaters are an even rarer, advanced stage of infected that succeeds the clicker stage. It takes the longest amount of time to occur and is subsequently the most powerful and largest known variant because the host has to be strong enough to survive the extensive infection. They are enormous in size, easily towering over the humans around them. The fungus has grown to an excessive degree, causing the body to bloat and forming fungal plates that act as body armor against attacks. This fungal armor is able to withstand barrages of bullets from assault rifles but another bloater in Jackson did eventually die to prolonged exposure to the fire from a flamethrower, albeit Tommy needing to unleash the entire canister to kill it.

Bloaters possess incredible strength; they could kill people with a single punch and rip them apart with ease, such as their signature jaw-breaking attack. Another was also capable of smashing through the walls of Jackson, pushing the pillars apart with its bare hands, enabling the runners to breach the town; in comparison, a full horde of runners and clickers were unable to repeat this feat. It is also said that they are capable of throwing spore projectiles at people, though it has yet to be verified due their rarity. Despite their immense size and strength, they are noticeably slower than the earlier infected variants, who can easily outrun them. Unlike the lesser infected who tend bite the uninfected, bloaters do not seem to be compelled to do so, as they outright kill them instead.

Stalker

By December 2028, a new variant of infected had evolved to demonstrate heightened levels of intelligence in combat. Ellie dubbed the one she encountered a stalker because it was capable of hiding in the shadows to surprise attack her. A lone stalker in Jackson would stalk Ellie by crawling around her at a distance, then lure her to approach it by creaking at her, choosing not to run at her like the other infected do. It then ran away and hid in a counter to then surprise Ellie from behind. It was still as vulnerable as other infected variants though, easily dying to gunshot wounds.

A large pack of stalkers was also present in Seattle, occupying an abandoned warehouse. They were left undisturbed by the WLF's patrols, the stalkers able to freely kill any wandering survivors who tried to cut through the building, including Seraphites. These stalkers were also intelligent, having bioluminescent eyes to see in the dark and would surround their prey. They were also adept at remaining near-silent, with Dina (known for being able to pinpoint exactly how many infected she can hear in an area) being unable to hear them. When Ellie and Dina faced the pack, they were overwhelmed by them, with three stalkers able to successfully distract and tackle Ellie and another two would have bitten Dina had Jesse not arrived and fought them off with his assault rifle. They were also uniquely shown to flee combat, with two of the stalkers running off after recognising Jesse as a threat they could not defeat.

Stalkers were the rarest type of infected, with the seasoned members of Jackson's council being unfamiliar with an infected capable of higher intelligence with some colloquially calling it "the smartest infected ever" or outright dismissing it as a fantasy.

Behind the scenes

• In the video game series, the early stages of infected are explicitly referred to as runners and stalkers, while the later stages are referred to as clickers and bloaters. Although these names were used on set and mentioned in interviews, the only term used in-universe during the first season was "clickers" in "Endure and Survive", while the bloater was credited at the end of the episode. Stalkers were later "semi-confirmed" by showrunners Craig Mazin and Neil Druckmann during a panel at SXSW 2025 promoting the second season and officially appeared in "Future Days". The term "runner" was also used for the first time in this episode.
• While the museum clickers are physically portrayed by Olivier-Ross Parent and Samuel Hoeksema, voice actors Misty Lee and Phillip Kovats reprise their roles from the game as the clickers' distinctive noise.
• The team behind The Last of Us spent a great deal of time during pre-production figuring out how to accurately portray the clickers. It was decided early on that they would be portrayed with prosthetics rather than visual effects, as Craig Mazin felt not having the physical creature would lessen the impact. The clickers were designed by Barrie and Sarah Gower, who previously worked with Mazin on Chernobyl. The designers frequently referenced art from the game in the process. Mazin noted it was important for veteran players of the franchise to recognize the clickers as the enemy they encountered in the game, and for new viewers to be terrified. The actors hired to play the clickers were fans of the game, and so were able to mimic the movements as well as make the noises during filming, though this was dubbed over in post-production. Both Bella Ramsey (Ellie) and Pedro Pascal (Joel) found filming the museum sequence in "Infected" immersive and terrifying due to having the clickers on-set and having to react in real time: Ramsey opined she did not have to act very much as she was genuinely scared by the clickers' appearance and movements.
  • The child clicker in "Endure and Survive" also marks the first time a child at this stage of infection is seen in The Last of Us franchise. This was an intentional choice by Craig Mazin, who wanted to contrast innocence with horror. She was played by contortionist Skye Belle-Cowton who was 9 at the time of filming.
  • The bloater from "Endure and Survive" was a mix between a practical suit, and CG imaging. The CG model was made by WETA FX, and the practical suit was played by Adam Basil.
• In 2023, reference was made to Pedro Pascal's (who plays Joel) connection with the HBO show in a promotional video for his then upcoming hosting of Saturday Night Live. In the video, Pascal encounters a clicker who in fact was a cast member on the show named Matt.

Gallery

Official stills

Joel and Tess inspect a dead infected.

Infected will often latch themselves to walls in order to continue cultivating the fungus after their death.

A clicker walks towards Joel, Tess and Ellie.

An adolescent clicker in Kansas City.

A bloater in Kansas City.

Ellie gets attacked by an infected.

Ellie stands next to the infected she just killed.

Behind the scenes

Neil Druckman speaks to Sam Hoeksma about his role as the main museum clicker.

Artists working on the practical bloater suit.

Barrie Gower poses with the practical bloater suit from Episode 5.