A Survival Guide to the Infected Fungus 'Zombies' of <i>The Last of Us</i>

Welcome, students of The Last of Us, to Fungus Zombies 101. In this seminar, we’ll cover the basics of what’s known as the cordyceps infection, how it spreads throughout a host’s lifetime, and why it ought to haunt your nightmares. Ready? Let’s dive in!

In the new HBO show The Last of Us—and the 2013 PlayStation video game that inspired it—the zombies are not, in fact, zombies. They never died, nor were they ever reborn; instead, a terrifying fungus crawled through their insides and took over control of their still-living bodies. Thus, the proper term for these creatures is “infected,” though “fungus zombies” is an oft-accepted colloquialism. (Just don’t tell game developer and show co-creator Neil Druckmann.)

There are four main stages of the cordyceps infection, plus one bonus stage we’ll get to in a bit. Each stage will only progress within the right conditions, whether time or environment. If those conditions aren’t met, some infected will remain in one state for long periods; others die before they’ve had the chance to evolve through the final stage. Regardless, all of them are violent, bloodthirsty, and capable of spreading the fungus through bites, spores, or—in the show—long tendrils of mushroom-like stalks. If that’s not enough to stir your survivalist instincts, read ahead for a few more reasons why you should invest in a good bunker.

In The Last of Us, there’s only one real hope against this wave of wobbling monsters: Ellie (Bella Ramsey), a 14-year-old girl who’s developed immunity against the fungus. Whether she’s really the answer to a long-awaited cure remains to be seen, so in the meantime, you’ll want to know the difference between your clickers and bloaters. Below, we’ll run through the types of infected—and dole out a few tips on how to outlive them. Study up, and mayhaps stay away from pancake mix.

Stage 1: Runners

Runners are the most humanlike of the infected, largely because they’re the most recently “turned.” Within two days of a bite (or breathing in a healthy dose of spores), but sometimes within hours, a human will lose control over their faculties and transform into a runner.

At this point, the fungus hasn’t yet had the chance to spread throughout the body and pierce the skin, so while runners’ minds might be a lost cause, their bodies still look deceptively human. You’ll know them, instead, by their hair loss and diseased-looking skin; their erratic, jerky movements; the snarls and screams that erupt unprompted from their throats; their torn, stained clothing and bloody mouths; and—if you dare look close enough—the tendrils of cordyceps that sometimes emerge from between their lips.

In the video game, runners are the easiest group of infected to kill, though they tend to attack in groups and move at extreme speeds (thus the moniker “runner”). The runners in the HBO show exhibit similar tendencies: In the premiere episode, a runner chasing Joel and his daughter is so quick it seems almost supernatural. But because these monsters have yet to develop any fungal armor, runners are susceptible to gunshots, knives, and any other weaponry that would take out your average pleb.

The internal awareness of runners is the subject of debate in the world of The Last of Us, but there’s evidence runners are still “awake” enough to recognize they’re no longer in control of their own bodies. (Some runners moan and shriek in agony even when they’re not under attack, and others seem resistant or even remorseful over their gory instincts.) It’s an ugly premise, one the show is likely to explore in more detail than the game.

Stage 2: Stalkers

Usually after two weeks post-infection, runners shift into stalkers, a stage they can remain in for over a year. At this point, fungal growth becomes visible on their bodies, peeling away skin and bursting through orifices. (If you get close, pray you have a good gag reflex.) These creatures begin to lose their humanlike sounds and instead emit croaks, though they’re still quiet enough to hide, track and attack their victims, earning them their “stalker” title. For this reason, they tend to prefer locations with plenty of places to hide; bonus points if it’s dark and moist.

Stalkers are also stronger than runners. By this stage, they’ve sprouted the beginnings of what, in essence, is mushroom chainmail. A simple fist fight ain’t gonna cut it, so shotguns and flamethrowers are often a better pick if you’ve got an arsenal at your disposal. But beware getting too close to a stalker that already seems deceased. The creatures are capable of temporary dormancy: They can attach themselves to buildings while they nap, allowing tendrils to emerge from their bodies and climb the surrounding walls. If awakened, they can break out of this shell and attack again. Others remain in this state until the cordyceps fully consumes their bodies and they die.

Stage 3: Clickers

After the first year of infection, stalkers phase into clickers, arguably the most iconic of The Last of Us inventions. They first appear in the second episode of the HBO series, when Ellie, Joel and Tess creep through the abandoned museum together. With enormous blooms splitting open their skulls, clickers are more fungus than human—with the exception of their mouth and teeth, which remain intact to snap at victims. You better believe that breath is foul.

Because the cordyceps has either covered, disfigured, or entirely done away with the body’s eyes by this stage, clickers are blind, but they make up for their inability to see with a bone-chilling form of primitive echolocation. The croaks that began in the stalker stage now become “clicks” as the infection spreads, and the clickers use this sound to locate humans and communicate with other infected. This ability is imprecise, sure, but that doesn’t make it any less creepy.

When aware of a potential victim in their midst, clickers are obsessive, utterly consumed with the task of finding (and gnawing on) the errant human. And when surprised or attacked, all bets are off; they go “berserk,” and you’d best have a really dependable firearm in your back pocket. (Or a Molotov cocktail! You carry those around all the time, right?) The better option is to try and outsmart them, sneaking away silently so as not to trip their unsophisticated echolocating alarms. Much stronger than runners and stalkers, clickers are tough to kill and even tougher to expunge from your dreams. Good luck!

Stage 4: Bloaters or Shamblers

Several years post-infection, stalkers grow into bloaters or shamblers, depending on the environment they grew up in. (Nature versus nurture, it comes for us all!) Now almost entirely fungus, bloaters—if in drier climates—or shamblers—if in wetter—have few, if any, human-like features apart from their bipedal movements. The encroaching fungus, by this point, has hardened into plates that provide significant protection, turning the once-human skin into something puckered and indistinguishable.

Both bloaters and shamblers are slow-moving and clumsy, though they make up for their two left feet with profound aggression. They can rip a human apart with just their bare hands, should they manage to grab you. Their low-toned “clicks” mimic a clicker, but their blindness is more pronounced and their echolocation even less refined. If you spot one, keep it zippy! Most frightening of all is their actual skin, home to glow-in-the-dark pouches of toxin or pus—toxin for bloaters, pus for shamblers—that they can unleash upon an enemy. These acidic weapons can burn and infect your skin, so layer up if you’d prefer not to deal with one seriously disgusting rash.

As for fighting them off, well, I wish you the best. You’ll want an army surplus store’s worth of ammunition, or at the least a dependable flamethrower. Once the fungal armor is burned away, bloaters and shamblers will be more vulnerable to gunshots, if you can keep your hands steady long enough to aim.

Thankfully, Joel and Ellie have yet to encounter a bloater in the HBO series. The keyword, of course, is yet.

Stage 5(ish): The Rat King

This section contains some minor spoilers, so breeze past if you’d prefer to sleep better at night.

In the sequel to the video game, The Last of Us Part II, there’s a technical fifth and final stage to the infection: a super-organism known as the Rat King. If, after multiple decades of infection and forced proximity, several infected hosts remain in the same area, it turns out that cordyceps is capable of weaving these hosts together, fusing them into one enormous mega-boss.

These symbiotic creatures are almost impossible to kill, given their advanced armor and speed. You’ll want not just guns but bombs to take them out, and even then the Rat King is still capable of splitting apart into individual stalkers, clickers, and bloaters.

The one comfort I can offer is that these creatures are rare. They require many, many years of contained infection without exterior interference. The Rat King in Part II, for instance, was made up of Seattle’s first patients, kept in quarantine once they were infected and never allowed to leave.

Stage 6: Death

Infected do, eventually, die. They either succumb to injuries or of something akin to old age, as soon as the fungus has consumed enough of the human flesh. At this point, the host will find a spot hospitable to cordyceps—usually somewhere dark and wet—and grow still, becoming a corpse while the fungus itself continues to bloom. Over time, the dead body will turn into a sort of fungal blanket, spreading over walls and surfaces and filling entire buildings with spores. (In the TV show—which did away with the game’s spores for logistical reasons—tendrils are instead the resulting threat.) Only sunlight is capable of annihilating this corpse-fueled fungus entirely; if a light shines on the growth long enough, it will become bleached and hardened, then it will die. That’s an apt metaphor for a narrative like The Last of Us, steered by the anti-authoritarian group known as the Fireflies and their motto: “When you’re lost in the darkness, look for the light.”