The Walking Dead: What is the Origin of the Zombie Outbreak?

The origins of the zombie outbreak have been left deliberately vague on The Walking Dead. But can we figure them out all the same?

The Walking Dead Zombie Outbreak
Photo: AMC

Back in the “Before Times” of January 2020, The Walking Dead creator Robert Kirkman fielded a Twitter question about a pandemic unrelated to the one that would soon seize the world.

“What was the origin of the zombie outbreak on The Walking Dead?” one Twitter user wanted to know. Kirkman answered the question simply and succinctly with: 

“Space spore.”

You may have noticed that the exchange above contains no links to the tweets in question. That’s because they no longer exist. Kirkman deleted his “space spore” tweet shortly after dozens of websites picked it up and ran with The Walking Dead Creator Reveals Zombie Outbreak Origin” headlines. 

Ad – content continues below

One could forgive the Internet Take Industrial Complex for taking Kirkman’s answer and running with it though. Kirkman has a decent track record of spoiler-reveals. Through 193 issues of The Walking Dead, he was fond of holding spoiler-y information over readers’ heads in his Letter Hacks Q&A sessions at the back of the book. Not only that, but Kirkman was once a contestant on Comedy Central’s @midnight and when host Chris Hardwick cheekily asked for an upcoming Walking Dead spoiler, Kirkman just flat out revealed that one day a character named Negan will arrive to kill Glenn on the show, several seasons ahead of the actual moment. 

Alas, this Twitter exchange was one of those instances where Kirkman really was joking. He confirmed as much in April via his account

In reality, Kirkman has always been adamant that the origin of the zombie pandemic on The Walking Dead would never be explained. And in the end, the writer was true to his word. The Walking Dead concluded its run with Issue 193 last year and nowhere in those 193 issues is there any indication of what kind of virus or supernatural event could have reanimated corpses around the world. 

For years Kirkman steadily maintained that the cause of the zombie outbreak was never important. He was more concerned with telling a simple horror (and later action/adventure) story with relatable characters. Zombies were inherent to that mission as antagonists and occasional environmental obstacles.

The closest Kirkman ever came to going on record in describing what caused the zombie outbreak was in the Letter Hacks section for Issue 147. In it, he explained just how someone becomes a zombie thusly:

“Just to get this on record once and for all… and it is complicated, I know… here’s how zombification works. Whatever makes people come back as zombies after they die–it’s inside them. It’s inside everyone. No matter how anybody dies, as long as the brain is intact… they turn into a zombie. Well… bites, and direct to blood contact with zombie gunk, […] causes death. It’s a strong infection that leads to fever that kills someone. Then the “virus” or whatever is already in them… turns them into a zombie.”

Ad – content continues below

Kirkman’s words there suggest that the cause of zombification is indeed some kind of virus. But ultimately, it was never important to Kirkman or the story to further elucidate what kind of virus can bring the dead back as shambling monsters. What was important was that the “rules” of the virus were understood. 

And both The Walking Dead comic and TV show made sure those rules were established early on. In the comics, it’s The Governor who reveals to Rick and Michonne that everyone is “infected” and will return as zombies after death. In the show, CDC doctor Edwin Jenner (Noah Emmerich) reveals this information to Rick. Jenner even has fascinating MRI footage of what happens to the brain once a person dies during the zombie apocalypse. After all the electrical impulses of the brain die down, the body cools for a couple of hours and then suddenly brain activity can be recorded in the brainstem – the most primitive part of the organ. 

Still, none of this actually establishes what the “virus” is – only how it works. The Walking Dead zombie virus does not have a name like the Cordyceps Brain Infection in The Last of Us. In fact, it might not even be a virus at all. No less scientific a mind as Edwin Jenner leaves the door open for a supernatural explanation and so too should we. 

And that brings us back to the space spore of it all. Yes, Robert Kirkman was definitively, canonically trolling with that answer. But it is a fun little nod to a path that The Walking Dead could have taken. 

Kirkman originally developed The Walking Dead as a Night of the Living Dead comic. But when Image Comics encouraged him to develop his own idea so that he could control the IP, he retooled the idea into something original. Even then, Image wasn’t fully sold on the idea. So Kirkman concocted aPlan 9 From Outer Space-esque tale of how the zombies were actually animated by an alien race that was preparing to invade Earth by disrupting its infrastructure.”

Ad – content continues below

That’s right: space spores. Ultimately Image accepted that concept but Kirkman just plowed ahead with his own, less fantastical version of The Walking Dead. Image must have known they were duped at some point but the comic was so big a hit that they likely forgot all about those space spores.