The click. It's the sound that defines a generation of survival horror. If you’ve played Naughty Dog’s masterpiece or watched the HBO adaptation, you know that sound isn't just a jump scare—it's a death sentence for the unprepared. But honestly, the biology behind the last of us infected types is way more disturbing than just some mushroom-headed zombies chasing you through a ruined Pittsburgh or Seattle.
It’s about evolution. Not the slow, million-year kind, but a frantic, parasitic takeover that turns a human being into a literal fungal garden. Most people think it’s just about how long someone has been bitten, but the environment, the host's health, and even the specific strain of the Ophiocordyceps unilateralis fungus play a massive role in what kind of nightmare walks out of the shadows.
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The Early Days: Runners and the Loss of Self
Runners are the first stage, and frankly, they're the most heartbreaking to deal with. Within 24 to 48 hours of infection, the host loses brain function. They’re still fast. Very fast. They look like people, but their eyes are glassy, and they make these horrific, gurgling moans that sound like they’re trying to scream for help while their vocal cords are being hijacked.
You’ll notice they move in erratic bursts. Unlike the slow-moving George Romero zombies, these things sprint because the fungus is basically overclocking their nervous system. They still have their sight, which makes them incredibly dangerous in open areas. If one sees you, the whole pack is coming. It’s localized chaos. In the games, they’re the "cannon fodder," but narratively, they represent the immediate horror of the collapse—people who were eating dinner two days ago are now ripping throats out.
Stalkers: The Creepiest Phase
Nobody likes Stalkers. Period. This is the second stage of infection, occurring anywhere from a week to a year after the initial bite. What makes them unique among the last of us infected types is their intelligence—or at least, their predatory instinct. They don't just run at you. They hide.
They’ll duck behind a crate, peek out, and wait for you to turn your back. The fungal growth starts to burst through the skin, particularly around the head, but they haven't lost their vision yet. They have this eerie silence about them. In The Last of Us Part II, the basement sequence in the hospital is the perfect example of why Stalkers are arguably more dangerous than the bigger types. You can’t just rely on Listen Mode because they literally stick themselves to the walls and go dormant until you’re within reach. It’s a psychological game.
The Sound of Death: Clickers and the Sensory Shift
Clickers are the icons. By this point, usually a year or more into the infection, the fungus has completely overtaken the host’s face. It splits the skull open. They are completely blind, but their hearing is supernatural.
They use echolocation. That clicking sound? That’s them mapping the room. If you throw a brick, they’ll sprint toward the impact. If you breathe too loud, they’re on you. Because the fungal plates are so thick on their heads, they act like natural armor. You can’t just pop a 9mm round into a Clicker’s forehead and expect it to go down; you usually need a shiv, a shotgun, or a well-placed molotov.
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What’s interesting is the sheer strength they possess. The fungus has reinforced their muscles and skeletal structure. They don't just bite; they tear. From a design perspective, Naughty Dog created something truly unique here—a monster that forces the player to be silent in a world that is already terrifyingly quiet.
The Heavy Hitters: Bloaters and Shamblers
When the infection lasts for years—usually a decade or more—and the environment is right, you get a Bloater. These things are massive. They’re slow, lumbering tanks covered in thick, calcified fungal plates. They are essentially walking fortresses.
- Bloaters are known for throwing "mycotoxin bombs." They literally rip pieces of fungal growth off their own bodies and toss them at you, releasing a cloud of toxic spores that eats away at your health.
- In the first game, the high school gym fight is the introduction to this nightmare. You can't grapple with them. If a Bloater grabs you, the animation is a "one-hit kill" where they literally rip your jaw apart.
- Shamblers are a variation found primarily in wet, humid environments like Seattle. Instead of physical armor, they focus on gaseous attacks. When they get close, they release a massive burst of acidic spores. Even if you kill them, they explode in a final "fuck you" cloud of toxins.
The existence of Shamblers suggests that the Cordyceps is highly adaptive. It’s not a linear path. If the host is in a swampy area, the fungus evolves differently than it would in a dry, desert climate. This biological nuance is why the world of The Last of Us feels so grounded despite the sci-fi premise.
The King of the Hill: The Rat King
We have to talk about the Rat King. It’s the stuff of nightmares. Found in the lower levels of the Seattle hospital, this isn't just one of the last of us infected types—it's a cluster.
It’s what happens when multiple infected people are trapped in a small, enclosed space for twenty years. They literally fused together into a giant, multi-limbed mass of fungal flesh. It’s the "Patient Zero" of the Seattle outbreak. The horror of the Rat King isn't just its size; it's the fact that as you damage it, smaller, hyper-powerful Stalkers and Clickers literally break off the main body and attack you independently. It’s a literal ecosystem of infection in one body.
Beyond the Individual: The Spore Problem
While the infected themselves are the immediate threat, the spores are the environmental killer. In the games, certain areas are so thick with fungal growth that a gas mask is mandatory. If you breathe them in, you’re done. The fungus starts growing in your lungs immediately.
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The HBO show changed this to "tendrils" to avoid having the actors in masks all the time, which is a fair trade-off for TV, but the spores represent the true "end of the world" feeling. The idea that a room can look perfectly safe but actually be a death trap is terrifying. It turns the architecture itself into an enemy.
Survival Strategy: How to Actually Deal With Them
Knowing the types is one thing, but surviving them is another. Most players make the mistake of trying to shoot their way out. That’s a fast way to run out of ammo and get swarmed.
- Stealth is King. Especially for Clickers and Stalkers. If you don't have to engage, don't.
- Bottles and Bricks. These are the most important weapons in the game. Use them to redirect Clickers or to stun a Runner for a quick melee kill.
- Fire. The fungus is highly flammable. Molotovs are the most effective way to deal with Bloaters and Shamblers because it bypasses their armor plates.
- The Environment. Use narrow doorways to funnel Runners so you don't get flanked.
The Cordyceps isn't just a virus; it’s a living, breathing, evolving organism. Understanding the last of us infected types is about recognizing the stages of a biological takeover. Whether it's the frantic energy of a Runner or the calcified strength of a Bloater, each stage represents a different challenge for survival.
Keep your ears open for the click. Check your corners for the Stalkers. And for heaven's sake, always carry a brick. The world ended because of a fungus, but you don't have to end because of a lack of preparation. Next time you're scavenging, prioritize supplements to upgrade your Listen Mode—it's the only thing that levels the playing field against a blind enemy that can hear your heartbeat.