The Walking Dead: World Beyond dropped a hint about the zombie virus' origin, and it falls in line with what franchise creator Robert Kirkman has said in the past. Ever since The Walking Dead comics and TV series released, fans have wondered how it all began. No one in The Walking Dead's world is familiar with the term zombie and even when the characters visited the CDC in The Walking Dead season 1, the only answer they got was how people reanimated into the undead.
The one question that has eluded characters in the universe and fans alike is how the zombie virus started. At one point it seemed like Fear the Walking Dead would resolve that mystery when season 1 took place during the initial outbreak, but while viewers were able to see the world crumble in ways The Walking Dead never showed, it still didn't offer any clues about the virus' origin. And then in summer 2020, Kirkman revealed what really started Walking Dead's zombie outbreak - though, in all fairness, he was most likely joking as it was a ridiculous answer.
Kirkman suggested a space spore caused The Walking Dead's zombie virus. And now in The Walking Dead: World Beyond season 1, episode 7, "Truth or Dare", a U.S. Marine says he heard that the virus came from space and made people sick. What the character says in World Beyond is far from confirmation of the zombie virus' origin, but it's at least a plausible theory and one of the only ones ever mentioned in the Walking Dead franchise thus far.
Another reason for the Marine mentioning the virus coming from space could be in reference to Night of the Living Dead. George A. Romero's movie is credited with launching the zombie genre in entertainment - and for good reason; it's one of the many cornerstones of horror and it's often cited as an inspiration for zombie movies, shows, and books, including The Walking Dead. In that film, an emergency broadcast suggests the zombie outbreak was caused by radiation from a returning probe from Venus, which exploded in Earth's atmosphere.
So it's possible that both Kirkman and World Beyond were referencing Night of the Living Dead, but it's still the only workable theory fans have to go on. The fact that it was mentioned in The Walking: Dead World Beyond could be important later down the line, as the Civic Republic's scientists appear to be working on a zombie cure - or, at least, trying to understand the fundamentals of the zombie virus. It's possible that season 2 could bring more answers about the virus' origin and how to ultimately defeat the walkers.