What is the virus in ‘The Last of Us?’

The official drop of HBO’s first full-length trailer for its upcoming adaptation of Naughty Dog’s The Last of Us has fans in a daze as they prep themselves to be re-traumatized by the upcoming series.

The utterly stellar video game series already has hordes of fans, so a live-action adaptation is all but guaranteed to land – assuming it approaches its source material with the respect and care it deserves, of course. The small amount of news of the series appears to paint a promising picture of what is to come — thankfully — and it’s ramping up excitement among fans of the franchise.

HBO’s The Last of Us isn’t aimed purely at returning fans, of course, and casual viewers were also intrigued by the recent trailer. They have far more questions than answers, however, as they stare the unique zombie story down. The undead in Naughty Dog’s gorgeously-realized release aren’t your average walkers, with some of them sporting grotesque, sprouting heads instead of the typical rotting flesh. These same creatures emit an eerie clicking sound to track down their prey, earning them the name “clickers” among survivors. Their appearance — and strange method of hunting — is prompting questions among those unfamiliar with the The Last of Us story. 

What is the Cordyceps brain infection?

The virus in The Last of Us is based on a real-world parasitic fungus, one that largely targets insects and other arthropods. The story in Naughty Dog’s games shifts the way the fungus works somewhat, but it leans hard on the real-world implications of this invasive infection evolving to affect humans. 

Humans infected by the cordyceps brain infection will quickly succumb to the brutal virus. They’ll gradually shift from mindless, shrieking killing machine to deadly clicker over the course of months, at least, gradually losing their ability to see but gaining a sort of echolocation. In The Last of Us, most clickers are fully able to move around, but many lurk out of sight, grown into walls in gross, fungal masses.

In the real world, the fungus The Last of Us bases its virus around is highly invasive, and quite unsettling. The fungus attacks its host and gradually replaces its tissue, growing to replace the destroyed tissue and eventually overtaking the host body completely. It often grows out of a host’s head, sprouting like strange, fungal-looking tentacles or growths. Many hosts affected by this brand of invasive fungi survive for painfully long as it slowly overtakes their bodies, a process that has unnerving similarities to that in The Last of Us.

The virus in the games works similarly, overtaking the host body and eventually robbing it of any autonomy. Fully altered clickers are uniquely deadly in the games, providing very little chance for escape once they’ve caught on to your presence. Their lack of eyesight doesn’t slow these brutal killers down at all. 

HBO’s series gave fans their first look at clickers in the recently released trailer, and they look absolutely perfect to fans of the games. The show clearly intends to provide an honest-to-origins interpretation of the disturbing creatures, and fans couldn’t be more excited for the series to set them loose on the small screen.

The Last of Us is expected to arrive on HBO Max in 2023.