Something that people argue about the speed of the infected one. Zombies that run fast, like in Left 4 Dead, Counter Strike: Zombie Mod (whatever), and Resident Evil, are usually something that have an extent of the infection. Slow zombies are usually the dead corpse reanimated, due to radiation or summonings in movies.
Louis: Wher- *hit by tank*
Civillian: They're sooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo- *is bitten*