I'm wondering where and why the zombie outbreak began?
The cause of the outbreak is not known. It has been made fairly clear that the initial source of the virus is not currently something that either the comic or the show are planned to address, as this quote from an interview with show producer Glen Mazzara indicates:
All we really know about the virus is:
We can also speculate that humans are likely the only animals that the virus infects.
All we can really infer from this is that the virus is likely airborne, due to how widespread the infection is.
"No explanation is offered for this behavior -- indeed, what explanation would suffice?" -- Roger Ebert
Logically there must have been a start to it, a Patient Zero, but that start wasn't revealed to us. The characters don't know how it started. Even Dr. Jenner of the CDC, who watched the progression of the contagion from the first reports, and had every possible research tool at his disposal, had no idea what it was and didn't seem to know where it really began.
This follows the real-life pattern of diseases like AIDS and Ebola. We can study them right down to their molecules, we can trace them back to a few square miles in Africa, but that might be as far as we ever get.
Not sure if it helps, the io9 article Everything you need to know about The Walking Dead explain why it has never been revealed.
TL;DR: We don't know, and according to franchise creator Robert Kirkman, who writes the comics and is an Executive Producer on the show, we never will.
Why We Don't Know - In-Universe:
They Wouldn't Know:
There are no newspapers anymore. No TV. No internet. No telephones. No radios. Information can only travel by word of mouth in the post-apocalyptic world. The people best suited to discover how and why the outbreak began - doctors and epidemiologists - were among the first to die. When the outbreak began, people who had been bitten went to the hospitals; then they died, turned, and quickly overran the hospitals. Doctors and nurses were in the greatest danger, and few survived the initial stages of the epidemic.
Epidemiologists like Jenner at the CDC were safer than hospital staff, but some were bitten, some lost hope and killed themselves, and as the world outside fell apart, many went home to be with their families. Soon, even those who kept working were unable to continue, because the infrastructure began to fail - they lost contact with the outside world, the water stopped running, and eventually, the power went out for good. As Jenner said, the scientists just didn't have enough time to figure out what was causing the problem, let alone how to fix it. And even what little they did know was impossible to share with anyone outside their own facilities, because the means of communication were breaking down.
It all happened so fast that the scientists trying to find a solution to the problem didn't have time to establish what was causing it, let alone share their findings with the public.
Realism - except for the existence of zombies, obviously - is important to Kirkman:
Kirkman wants TWD to feel real. The closest the TV show came to explaining the outbreak was the last episode of season 1, when the group went to the CDC and got a tiny bit of information. This actually never happened in the comics, and this is one of many cases where the comics beat the show. The CDC episode seems unrealistic and artificial, because the odds of a random group of people getting there, being allowed in, and finding the last man standing is ridiculously small.
Kirkman himself has said the CDC episode was by far his biggest regret regarding the show:
So they know almost nothing on the show, and even less in the comics - and Kirkman prefers the latter.
It Wouldn't Matter Anyway:
How would knowing how and why the outbreak began help people like Rick's group? It wouldn't. All they need to know is that the world has ended, strangers can't be trusted, walking corpses are everywhere trying to eat people, and you can kill them by destroying the brain. That would be true whether the outbreak was caused by a virus, or bacteria, or a fungus, or radiation, or magic, or aliens, or an act of god. They might wonder about it in their rare moments of peace and safety, but having the answer wouldn't change anything. They are desperate people fighting to survive a living hell.
People in The Walking Dead aren't obsessed with finding out how the outbreak began, for the same reason people floating around on the ocean after the Titanic went down didn't wonder which glacier the iceberg that sank the ship came from, how big it was, or when it calved. In both cases, there were much more important things to worry about.
If You Were In Their Shoes, You Wouldn't Know Or Care Either:
Picture yourself in the group's situation:
So, now that you've imagined all of this, what part of the story makes you think you'd know how, why, and where the outbreak began? What part of the story makes you think you'd even care, when you're so busy worrying about when the next attack will happen, how you're going to get food and water, when a herd too big to fight off is going to show up, how long it will take for the people in your group to turn on each other, and when armed raiders will storm your camp, rape and murder everyone in it, and steal everything in sight?
This was Kirkman's reasoning when he decided that we shouldn't learn anything specific about the origins of the outbreak.
Word of God - Why We Don't Know, Out-Of-Universe:
Franchise creator Robert Kirkman, who writes the comics and is an Executive Producer on the show:
The Walking Dead Showrunner and Executive Producer Scott Gimple:
Former Showrunner and Executive Producer of The Walking Dead Glen Mazzara:
Fear the Walking Dead Showrunner and Executive Producer Dave Erickson:
Fear the Walking Dead Executive Producer David Apert:
If this were really happening, it is totally plausible that no one would know where or how it began.
We haven't been told how it all started, and chances are, we never will be. Kirkman dislikes it when zombie media explains too much, and has been careful to avoid following the same path as his predecessors. The closest any The Walking Dead format has come to explaining the origins of the outbreak was in the first season finale of the original show, and - not coincidentally - Kirkman calls that episode his biggest regret, vis a vis the TWD franchise.
In the webisodes a terrorist attack was mentioned. At the end of series 2 it was revealed that everyone is infected and they will reanimate after death. There would have been a further explanation to the outbreak in a planned webisode. Remember, in series 1 when Rick jumps in the tank and there is a walker in there? Well this was to be the ending of the planned webisode. The walker was a US Army Ranger in Atlanta trying to evacuate the population during the outbreak but the city was overrun. This webisode was shelved due to budgeting issues. It is a shame because it would have given us a picture of what happened prior to Rick waking from his coma at the hospital.
In the comics, and I am just assuming the show, it is an infection. It is not believed to be air-born but basically everyone has it. You fall down stairs and break your neck, you're a zombie.
Quote from Robert Kirkman:
He has also said he won't reveal the cause in the comics so we will have to wait to see on the TV show but I wouldn't hold your breath. I guess it is up to the viewers own imagination.
There can be many explanations for the outbreak of the infection:
In the TV series, they differ greatly from the comic book series, in the TV series the infection is more closely and probably intentionally styled after the Solanum Virus from "The Zombie Survival Guide" and "World War Z". The difference being is that with the Solanum Virus or with the Walking Dead, everyone is already infected. But bites cause a lethal infection that kills you, and then you are reanimated. How this started is a little sketchy, I imagine the virus that everyone was already infected with mutated and when someone died they came back.. this is probably why infections started out in multiple locations and there is no true "patient zero"
protected by Community♦ Oct 15 '12 at 12:52
Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).
Would you like to answer one of these unanswered questions instead?