Walking Dead: World Beyond Finally Reveals Cause of Zombie Apocalypse

There are some secrets in TV and film that are never revealed, and fans of The Walking Dead long since gave up on finding out what caused the zombie apocalypse in the TV universe based on the Robert Kirkman comic book series. However in the post credit scene of Walking Dead: World Beyond, the spin-off series has done what Kirkman avoided doing in the entire run of the source material and given viewers the answer they have been waiting for over ten years since the show began: Exactly how did the zombie virus begin?