In The Last of Us video games, the Cordyceps brain infection originated in South America. Its means of transmission was through a bite, or by spores in the air. HBO's live-action adaptation completely removes the latter from the equation, which explains why Pedro Pascal's Joel isn't lugging around a gas mask.

The TV show's record-setting premiere episode hinted at this and the equally-successful follow-up that premiered earlier this week confirmed it. This subtle change makes HBO's The Last of Us scarier and more horrific and, in some ways, better than the source material.
The opening sequence of Episode 2 of HBO's The Last of Us confirmed the origin theories floating around since last week, as it documented the fungi's origin in Jakarta, Indonesia. The show features a mycology professor named Ibu Ratna, who claims it's impossible to develop a vaccine and that the only solution is to "bomb" the entire city to prevent it from spreading.
According to the show's co-creator, Craig Maizin, this was all Neil Druckmann's idea, telling Inverse that this one scene was the "scariest moment" for him.
That's high praise from someone who won awards for creating a miniseries based on a nuclear disaster.
Another significant change from the source material is the introduction of a hive mind of tendrils spreading across several miles. As the show explains, disturbing a live tendril can alert all the nearby infected and send them careening towards the affected area. By removing spores from the equation, HBO's The Last of Us raises the stakes for humanity as it effectively forces survivors like Joel and Ellie to be more mindful of every step they take.
HBO's The Last of Us is only two episodes in and it's already generating this much discussion.
As fans eagerly await for each episode of the show's nine-episode run to premiere, it appears some are checking out the original video games. The Last of Us Part 1 recently saw a spike in sales in the United Kingdom, climbing up sales charts nearly six months after the re-release was launched.
This bodes well for the launch of The Last of Us Part 1 on the PC on March 3, which will be days before the penultimate episode of the show arrives.