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Why The Last of Us creators swapped spores for Cordyceps networks

The short answer: An HBO version had to be watchable

A shot of an infected person stuck to a wall with overgrown mushrooms in The Last of Us Photo: Liane Hentscher/HBO

You’ve probably noticed by now that the fungus in HBO’s The Last of Us show works a bit differently than it does in the games — particularly in how the Cordyceps fungus, based on the real-life fungus of the same name, spreads among humans. Spores are out, and the mushroom network is in.

Spores serve the games’ eerie atmosphere well: With the right light, you can see spores spilling out from cracked doors, a warning of the danger that lies within. It’s the signal that the characters, typically Joel, must put their masks on in order to avoid infection, though Ellie’s immunity means she’ll only ever need a mask to blend in. But there’s no way the gas masks could work in the show. You can’t have your main characters’ faces hidden behind a bulky mask; this isn’t The Mandalorian, after all.

“The show [is] taking a more realistic approach to the story and the world,” The Last of Us writer and co-creator Neil Druckmann told Polygon. “If we wanted to treat it realistically, and there are spores near, characters would wear gas masks all the time. Then we lose so much, which is maybe the most important part of the journey is what’s going on inside behind their eyes, in their soul, in their beings. For that logistical reason, we were like, Let’s find a different vector.”

The vector Druckmann and The Last of Us’ writers chose was the mushroom network. It’s a concept based on the real-life science of mushrooms: We see mushrooms when they burst through dirt. The pieces we see are the fruiting bodies of the whole organism; the rest lies hidden underneath the surface of the Earth. That part is called the mycelium, the threads that spread underground and connect mushrooms and trees into a “mycorrhizal network,” a natural network not unlike the internet — some mushroom experts call it the “woodwide web.” Trees, mushrooms, and other plants use these networks to transport water and other nutrients and to “communicate” in different ways, often extended for miles and miles.

The mushroom networks, made up of sprawling tendrils, work the same way in The Last of Us on HBO, but instead of transferring information about where nutrients need to go, they alert the network of infected to a potential host: humans. Individual infected people join the “network” as spindly tendrils grow into an opening in their body, often a bite. (In episode 2, we see a more unique method of spreading: An infected body leans into Tess for a kiss, tendrils sprouting from his mouth into hers.) The fungus spreads quickly and overtakes all functions except the urge to spread.

“[We wanted] to feel like these things are interconnected. They can come out against us as a mass,” Druckmann said. “But also how they pass it from one person to the other, it just became this really disturbing thing, which was like, Oh, this is delicious. We have to use this.”

The change from spores to tendrils and the mushroom network adds another layer of tension to the way the infected work. It’s no longer enough simply to stay stealthy and quiet — one wrong move could mean activating a network of monsters that move en masse and know your exact location.

It’s a good change — in the video game, spores themselves don’t pose a threat. You can’t choose when to put on a gas mask or when to take it off; the developers made that decision for you, and the player is just along for the ride in that sense. Take the gas masks away, and the game wouldn’t change very much. It’s just something that happens: gas masks on and then gas masks off.

There’s also the consideration of framing the show around an airborne pandemic, like gaming website Kotaku wrote after the first episode premiered. The Last of Us can be a hard watch in that regard, and potentially a reason why the concept of spores was axed in favor of a mushroom network. After all, there’s still that same sense of mystery with the tendrils, but with the added tension of the communication between infected. Mushrooms have a map of the world that’s invisible to anyone else; their only goal is spreading the fungus.

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