The Walking Dead's Zombie Virus Origin Explained

"The Walking Dead" is full of mysteries, and for most of the series's existence, the origin of the zombie virus was the biggest mystery of all. Rick Grimes (Andrew Lincoln) and all the other series mainstays learn plenty about the walkers that have overrun the planet, but they never do figure out where the zombies came from in the first place.

The "Walking Dead" spinoffs helped give us a global view of the zombie apocalypse, but only one revealed the biggest secret in the franchise. A post-credits scene in the Season 2 finale of "The Walking Dead: The World Beyond" takes viewers to a biomedical lab in France, where a woman is desperately rooting around in dusty cabinets for computer drives. After watching an old video from Dr. Jenner (Noah Emmerich) at the Centers for Disease Control, she's approached by a man who's training a gun on her. The man claims that the woman and all the other researchers who had once worked for the facility were responsible for creating the zombie virus. Before she can say much more, he shoots her, and the scene ends with her corpse rising up as a zombie.

That post-credits scene does tie back to the very first season of "The Walking Dead," but its implications for the franchise at large are hazy at best. Despite being one of the biggest reveals in the show's history, the zombie origin story is an easy thing to miss in "The Walking Dead." It's also worlds away from the origin story that creator Robert Kirkman once hinted at in the comics.

"The Walking Dead" has been hinting at the origin of the zombie virus since the show's earliest days. Season 1 ended with our survivors arriving at the CDC headquarters outside of Atlanta. There they meet a scientist named Dr. Jenner who tells Rick a terrible secret about the virus. Dr. Jenner dies, but Rick eventually reveals his secret in Season 2. The doctor didn't know where the zombie virus came from, but he did know that every living human on the planet had already been infected with it. Everyone who dies is doomed to become a walker.

Now we know that Dr. Jenner was actually in communication with the French lab that started it all. Does that mean he, or some of his fellow scientists, were getting close to a cure? That was certainly something that Dr. Jenner and the woman investigating the research facility wanted, but now that all the scientists are dead, their research is virtually useless.

We know from the overall "Walking Dead" timeline that zombies are still roaming the Earth more than a decade after the collapse of civilization. For most of the people still alive, the origin of the virus doesn't matter anymore. The post-credits scene from "The World Beyond" does include some hints about the zombie variants that would later appear in the "Daryl Dixon" series, but the scene's most dramatic reveal has almost no impact on the franchise as a whole.

There are some things that only comic book fans know about "The Walking Dead," and for a long time the origin of the zombie virus was one of those — sort of. For years there were hints and jokes in the pages of "The Walking Dead" that the infection might have come from space. Then in 2013, there was an issue that included a short side story called "Small Bites," written by Derek Hunter, that addressed the origin head-on. "Small Bites" made it clear that an alien ship crashed on Earth and inadvertently instigated the zombie apocalypse.

"Small Bites" is clearly written outside the normal style of "The Walking Dead," and because of that it's tempting to write off the alien origin story as a joke. If it is a gag, though, it's one that series creator Robert Kirkman is very committed to. Kirkman was asked in 2020 about the zombie virus origin by a fan on Twitter, and the writer stated plainly that zombies were created by a space spore. Kirkman is also the creator of "Invincible," so fans know that he does have extraterrestrial threats on the brain — just don't expect aliens to appear in the TV show version of Kirkman's zombie universe anytime soon.