Infected are a 21st century spin on the classic cinematic zombie. Unlike typical zombies which are dead people who have been reanimated, infected are still alive but driven to a state of uncontrollable rabid behaviour due to being affected by some form of pathogen. What really makes infected stand out from other zombies, however, is that they are capable of running at an athletic pace whereas classic undead zombies can only walk slowly and are easy to avoid. Infected are usually more intelligent, though still reduced to an animalistic state and rely solely on instinct rather than any higher cognitive thinking.
Infected have appeared in such horror films as The Crazies, the 2004 remake of Dawn Of The Dead and, perhaps most notably, 28 Days Later. And just like their classic zombie counterparts, they are just as prone to being killed off in droves.