Warriors: Flesh-Sickness

Warriors: FleshSickness The Clans were nearly wiped out after the apocalypse occurred by a zombie-like disease that spread to animals, though some cats had genes in their blood that were strong enough to combat the virus, and they survived. As a result of this, the four Clans are incredibly small, and all of them live in the same territory, all of them too unwilling to leave the safety of the forest.
The fallout of the virus, named Flesh-Sickness by the cats, has infected other cats as well as other animals, making Warriors primary job to protect the hunting warriors during hunting patrols. This is not unlike the Tribes, which is where they adapted it from. The Clans now also cannot fight, or try not to, to stay alive. Cats that are too much of trouble-makers are fed to those infected with the Flesh-Sickness, which is the same with stillborn kittens or those with defects.
The Clans themselves are also now referred to as Survivors, and StarClan is abandoned. To them, strength and survival are more important than religion now.
"Only the strong will live. The great and strong will not yield to the weak and feeble, and those who are not must change their DNA if they would like to appear as our equals- and that in it of itself is a difficult task for kits who cannot even hear me speak." -Shellstar, leader of the fourth Survivor Clan (AKA: what once was RiverClan)