Although the playable characters are immune, a comment by Bill suggests that they could become an Infected at any point. The term, however, is commonly used to refer to the eight playable characters from the Left 4 Dead game series. The Survivors are people in the world who either have not yet contracted the Infection (by virtue of natural immunity) or are carriers of the disease but who display none of its symptoms―and who may thus falsely believe themselves to be immune.
