The stages of infection in The Last of Us

The Last of Us is a post-apocalyptic action adventure that has survivors fighting against zombie-like beings that Naughty Dog refers to as the "Infected." Although they featured heavily in the game's debut trailer, they've since taken a backseat. At a recent press event in Los Angeles, we finally had a chance to get our hands on the game--and fight these non-zombies. The inspiration for the Infected came from ophiocordyceps unilateralis, a type of fungus that takes over ants, transforming them into undead vessels to spread their deadly spores. When infected, the fungus essentially eats the ant alive, altering its behavior in the process. The development team wondered what would happen if the fungus could have a similar effect on humans.

Runners are not unlike traditional zombies

There are multiple stages of infection. In our hands-on demo, we were able to play against two. The first were called "runners." These poor saps have only recently been exposed and are at "stage one" of the infection. "They can still see, and they still have a sense of humanity. They almost know consciously what they're doing, but they can't control themselves," creative director Neil Druckmann explained. "They run fast, they can take you down, and they work in packs." The zombie equivalent would be the zombies from 28 Days Later. Slowly, the infection becomes increasingly visible, leading to the mushroom-headed beasts we saw in the game's debut. "As the fungus spreads, it takes over more and more of the biology of the human. It grows out of the eye sockets, and it makes you go blind. This is a fate worse than death," Druckmann explained. "You're still alive, but you have to suffer through this pain."

Clickers will kill in one bite

"Clickers" represent stage three of the infection. "They're called clickers because they use echolocation. They scan the environment using sound waves… if there's any movement detected, they're on you," Druckmann described. "They might be a little slower, but when they're on you, they're going to be rabid. when they touch you, you're gone." Yes, a single bite will result in a game over--regardless of how much health remains your life bar. As such, a single clicker is already unnerving to deal with--but a pack of them?

Eventually, the fungus will take over the entire body

Eventually, the fungus takes over the body completely. In one section of the game, a body was grafted onto the wall, as the bulbs outstretched beyond the body. Creepy stuff. The Last of Us will be available on PS3 this May. For more, read our full hands-on preview.