"Infected" is the second episode of the fourth season of the post-apocalyptic horror television series The Walking Dead, which aired on AMC on October 20, 2013.

The survivors realize the gravity of the situation, just as walkers attack the prison's exterior, and Rick Grimes (Andrew Lincoln) is confronted with abandoning his quiet lifestyle.

Michonne, trapped at the prison gates with two walkers, falls over a snare and is nearly overpowered before being rescued by Carl and Maggie.

As Carl and Maggie carry Michonne back inside, Rick approaches them and warns them to stay away from him and anyone else who may have been exposed, due to the risk of infection.

The council begins quarantining those known to be sick, including Karen and another prison inhabitant, her and Tyreese's friend, David.

As the survivors bury the dead, a massive group of walkers converges at a single portion of the fence.

Sasha points out the carcasses of several dead rats at the fence, suggesting that someone has been feeding the walkers, which lures them in and causes them to cluster together instead of spreading out.

Upon its original airing, "Infected" earned 13.95 million viewers and a 7.1 rating in the adults 18-49 demographic.

Club, gave the episode a "B" grade, and commented that the virus "as a plot mechanic, it's credible, but not exactly thrilling.

"[3] Roth Cornet of IGN scored the episode an 8.5 out of 10, and praised that each character is getting their own storyline, and that the episode "deftly harmonizes the dramatic and horror elements, while propelling the central characters forward in some of the more interesting story arcs on the series to date.