Plot summary
The reanimated Patrick manages to attack other survivors in a cell block, and the group is forced to kill off those bitten and relocate the others to a different block. They discover a deadly flu strain, brought by pigs that Rick tried to raise, affecting some of the survivors and which killed Patrick. Those infected are isolated, fearing they will reanimate when they die. Tyreese discovers his girlfriend Karen and her friend David, both considered infected, were killed and burnt by someone unknown.
Credits
Adapted from Wikipedia contributors, The Walking Dead season 4. HTML formatting and reference markers removed.