This article contains spoilers for The Last of Us Part I and Part II
Ellie’s immunity to the Cordyceps infection is an important part of The Last of Us game lore. In both the HBO series and the video games it’s based on, Ellie is the only person we know of who doesn’t become infected after being bitten or exposed to the Cordyceps in other ways. In the final level of The Last of Us Part 1, we learn that Ellie still has the Cordyceps fungus within her brain, it’s just a further mutated version that is essentially benign in that it doesn’t cause her to mutate. But since the Cordyceps fungus is technically still inside of her, does that mean that Ellie can then infect others?
While zombie movies like 28 Weeks Later have shown that even asymptomatic carriers of a deadly infection can still pass it to others, The Last of Us Part II shows us that this isn’t the case with Ellie. Though Ellie does bite David while trying to escape from him in The Last of Us Part I, he dies before we can see if he becomes infected. It isn’t until years later that Ellie is able to figure out that she isn’t contagious. During the Part II flashback level “finding strings,” that appears during Ellie’s second day in Seattle, we can read a journal entry where a sixteen-year-old Ellie wrote about getting a tattoo to further cover the bite on her arm, her first post-bite kiss with another girl in Jackson, and the initial fear of infecting someone else that followed.
In this entry, Ellie says “I’ve just had the worst/best day of my life! Cat was finishing another session on my arm and then climbed on top of me and kissed me. I threw her off of me. I yelled at her. I thought I infected her. I mean… I’m infected… sort of. I don’t know how the fuck this shit transfers. What if she turns? What would I tell people? She’s got family .I told her we should take a walk. I lied and said I’d never kissed anyone and that I was just nervous. She was actually sweet about my freak out. We spent the day walking and talking. Then she came to my place for a movie. She fell asleep… I stayed up all night watching her. Looking for signs of infection. The next morning she was fine. Nothing. I’m not contagious! And Cat likes me!!! What a fucking rollercoaster!!!!”