From The Walking Dead to Dawn of the Dead, from 28 Days Later to Dead Rising, anything that contains zombies has this logical fallacy:
A zombie apocalypse is factually impossible.
Given the behavior you normally see in books and movies, even with fast zombies, the zombie method of spreading infection (bites or scratches) is not sustainable enough to generate the zombie hordes required to topple modern civilization.
Why is that? Because zombies don’t just bite you. They consume you.
How could this be?
It may not seem like much of a fallacy, until you look at it a little more closely.
When a horde of zombies descends on its prey, what do they do? They rip the body limb from limb and consume it. They don’t just take a chunk of flesh and walk away. They consume you, brains and all.
In reality the condition of a zombie victim would be far more gruesome. The resulting corpse would be completely non-functional. At best it would be mostly incapacitated.
How could hordes of functional zombies be generated then, if the majority of people who get attacked by zombies are eaten? They couldn’t.
A zombie apocalypse, given the normally described methods of transmission of the condition, is not a scalable infection model. If a zombie virus manifested itself in reality, it would peter out within the first few infections because 99% of the victims would not be capable of rising up to infect others.