How Did The Last of Us Infection Start?

Fungi seem harmless enough...

by Matthew Kevin Mitchell

Are you wondering how The Last of Us infection started after watching the first episode of the highly anticipated HBO TV series adaptation? Of course, an infection wipes out humanity, and being infested by zombie-like creatures is not a new story, but The Last of Us takes a unique and surprisingly realistic approach to the genre. Neil Druckmann mentioned in an interview that the infection in The Last of Us was inspired by a BBC documentary where a fungus infects and kills various insect species. So then, how did The Last of Us infection start, and why was it so devastating to humans? Here is everything you need to know about the origin of The Last of Us infection and how it was able to decimate humanity.

How Did The Last of Us Infection Start?


The Last of Us infection is called Cordyceps Brain Infection (CBI), a parasitic fungal infection. CBI originated in South America and spread to humans through infected crops. The infection began spreading to the United States in the video game in 2013 and the HBO series in 2003. During the game’s prequel, we learn that hospitals in Joel’s hometown of Austin have spiked by 300% due to an unknown infection. Unfortunately, 60% of humanity died or was infected by CBI only several months after the initial spread. Once infected, the fungus grows in humans while they are still alive. The host will then go through four stages of infection until it eventually kills them.

The opening scenes of the new HBO series take us back to 1968 when scientists were talking about the possibility of a pandemic caused by fungus evolving because of the temperature of the Earth growing warmer. The ability of a fungus to withstand higher temperatures means it can withstand the higher temperatures within a host (in this case, humans).

An evolved fungus would then be capable of burrowing into our brains and taking control of humans. This would then create billions of puppets with poisoned minds permanently fixed on one unifying goal: to spread the infection to every last human alive by any means necessary. The doctor continues by saying that with no cure, there is no preventive measure humans can take to stop it. While everyone thought he was crazy, we can see 35 years later that he was right.

The Last of Us will have new episodes released weekly exclusively on HBO starting January 15, 2023.

- This article was updated on January 16th, 2023