the lore threads are not necessarily insightful .. the essentials are that a zombie virus swept the world around 14ish years ago, maybe 15 now .. definitely zombies and not just infected, as the host dies and is reanimated .. the disease itself was studied heavily (though, it would seem, to little effect as they were unable to stop it). However, characters who have been around the block would know there's more going on besides just zombies. There's talk of flesh-eating fog and of horrible mutant monsters in some locations.