The show is centered around the parasitic Cordyceps fungus - which tends to infect insects - evolving to control the human race and according to the showrunner Craig Mazin, is 'real.'

The episode ended with Tess (Anna Torv) sacrificing herself to save Joel (Pedro Pascal) and Ellie (Bella Ramsey).

It takes someone over a decade to reach stage four of the infection where they develop hardened fungal plates, release infectious spores, and are increasingly difficult to kill.

The Last of Us is a small-screen adaptation of Naughty Dog's best-selling 2013 motion-capture video game of the same name, which appeared to be heavily inspired by AMC's The Walking Dead and Alfonso Cuarón's 2006 film Children of Men.

'We are thrilled to see fans of the series and game alike experience this iconic story in a new way, and we extend our gratitude to them for helping to make it a success,' HBO chairman Casey Bloys said in a statement.

Source material: The Last of Us is a small-screen adaptation of Naughty Dog's best-selling 2013 motion-capture video game of the same name, which appeared to be heavily inspired by AMC's The Walking Dead and Alfonso Cuarón's 2006 film Children of Men