Infected was first popularized with Halo 3 in 2007, and first debuted in an unofficial capacity for💹 CoD in private matches within 2011's Modern Warfare 3.

Infected, also known as Sickness as an April Fool's day💹 joke, is a custom game mode introduced in Call of Duty: Modern Warfare 3, which started as a private match💹 game mode before being released to the online community public playlist on February 5, 2012 for PlayStation 3 and Xbox💹 360, and on May 9, 2012 for PC.