History
Some years before the planet was ravaged, Punisher observed a deal between an unknown and Red Mafia that involved exchange of nuclear suitcase at the dockside warehouse. Punisher did his job as always, shooting the goons down without mercy, whilst keeping the suitcase intact. However, the items weren't in the suitcase, but were rather concealed in metal vials that were strapped in their vests, which dissipated in form of green vapour on being shot. At first, Punisher thought it was liquid nitrogen, but it turned out to be a form of bioweapon, later known as Survivor-118 which quickly spread over the entire planet. Punisher, being heavily exposed to it, puked but wasn't turned into a cannibal because he developed some sort of immunity which he himself was surprised to hear. Over time, people were turned into mindless creatures, starting off when Spider-Man had a fight with Rhino which ended up with Spider man biting a part of Rhino's flesh off his neck, killing him. Next victim being Blob, who devoured everyone in a Chinese restaurant. Even after many researches and knowing that it was a cannibal inducing chemical, it wasn't stopped and slowly the world became a cannibal apocalypse. Researchers like Mr. Fantastic and Black Panther went towards the north pole to save themselves as well as find a solution to end the widespread infection. Unfortunately, they failed and many heroes and villains alike were turned. Those who remained like Captain America and Iron Man tried their very best to protect themselves and the remnants, but were killed or turned, right after they took refuge under Dr. Doom, who seemingly granted protection, but was a cannibal himself that was noticed by Hawkeye when he was brought Mystique's carcass in the form of a Thanksgiving turkey by Deadpool and turned many others into cannibals by convincing them to wear Doomstones to preserve their intelligence, which in reality were probably laced with the same chemical and turned red on activation. Then came teams formed by cannibals which were gradually either merged with King of Death or swept away. At some point, he abducted the wife of Spider-Man (now Patient Zero), Mary Jane, which made Zero lull Punisher into working for him to free his wife in exchange of getting survivors, which Punisher unwillingly accepted. After wiping the last tribe as said by Zero, the transaction was completed, but Punisher shot Zero in the head and sent the survivors away, leaving him to finish the job.
Trivia
As with Zombies, the contagion is spread through bites.