The Cordyceps Brain Infection, shown in “The Last of Us,” is actually a real fungal infection that is known to alter the mind of ants and other insects and accounts for their erratic behaviors. There are many other concepts and ideas that were taken by Neil Druckmann from the real world, though they have been modified in order to fit the narrative. In the second episode of the series, “The Last of Us,” we realize that people inside the quarantine zone had a very erroneous perception of the open area. There were stories made about what the areas outside the safe zones would look like. That is why, when Ellie comes out, she asks Joel and Tess why she isn’t seeing any infected people because they should have been swarming like bees all over the place. That’s when Tess and Joel tell her that reality is very different from what people think and believe inside the quarantine zones. Joel said that people like to make stories, but there were many things that they were unaware of.
The infected had a specific set of attributes, and though Joel and Tess didn’t know everything about them, because of their frequent visits outside the quarantine zone, they knew much more than the general populace. Joel and Tess constantly communicated with Bill and Frank, and the picking and dropping of their smuggled consignment would have been happening outside the quarantine zones. Ellie was petrified when she heard the echo of the infected for the first time; it sent shivers down her spine, and she realized that having knowledge about a threat and facing it in real life were two different things. Joel asked them to keep moving as he sensed that a colony of the infected was somewhere nearby, and if they got a hint that there were normal people in the vicinity, they would definitely attack.
Ellie saw a huge number of infected people crawling on the ground from the terrace of the abandoned hotel. That’s when Tess told Ellie that the victims of the Cordyceps Brain Infection were connected in ways that she couldn’t imagine. Tess wanted to warn Ellie and make her realize that even if she couldn’t get infected, the zombie-like creatures could hurt her in many other ways. Tess knew that there would come a time when Ellie would come face-to-face with the infected, and she wanted her to be prepared for that. Tess told Ellie that the fungus grew underground as well and that there were extremely long fibers, stretching over miles through which they communicated.
In case a person infected with the fungus was killed or affected in any manner, every infected person in the vicinity was woken up from their slumber. They probably had some sort of threat detectors through which they communicated and as soon as one was killed, all the others came running to that exact location. Be it the runner, clicker, or stalker, none of them could see but had a keen sense of hearing. They could hear voices that a normal human being couldn’t, and that’s what made them even more lethal. It is quite possible that, just like bats, the infected also put their echolocation to use and found out their prey. The bats sense the presence of an object through their high-pitched sounds, and the infected were probably applying a similar sort of system.
The theory of fungi communicating is not alien to the real world, and there has been evidence of the fact that they have cells that are capable of replicating behaviors generally seen in more complex organisms. According to medical research, a specific type of mushroom could sense the presence of predators in the real world and communicate the threat to different parts of their bodies. Scientists still don’t know how they do that, but they have enough evidence to prove that even primitive organisms have the potential to communicate like plants and animals and show such complex behavior. Apart from communicating information, Oyster mushrooms, that are carnivorous in nature, devour roundworms by releasing a toxin and poisoning their prey. In the present case, the Cordyceps was itself the predator, and as soon as one learned about a prey, the information was quickly transmitted throughout their colony. Though fungi can thrive in any kind of environment, they mostly grow in soil or latch onto a host plant material, displaying their parasitic traits. Fungi are known to have the capacity to cause pulmonary infections in human beings, and a lot of times, the infection can spread through the blood and reach the central nervous system if the immune response of a person is weak. One more remarkable aspect that scientists found about fungal cells was that they have the ability to sometimes trick the immune system and enter the body of a person without activating their internal defenses.
In the second episode of “The Last of Us,” we saw that Joel killed an infected person while the trio was having a conversation about what their next move should be. Tess was bitten, and she knew that there was no hope left for her. She wanted Joel to realize that he actually had a chance of winning the battle against the Cordyceps Brain Infection. She wanted him to accept the fact that Ellie was crucial to their survival and entertain the possibility that a vaccine could be developed through her. Tess wanted Joel to be hopeful. She wanted him to fight for what was left instead of being stuck in the past and crying over things that couldn’t be changed. In the subsequent episodes, we will get privy to other traits and characteristics of the fungus, and it could be possible that in the later stages of infection, like in the shambler, bloater, and rat king stages, the fungus shows even more complex behaviors that were still undiscovered by human beings.