relevant XKCD.

That aside, I think the book I am Legend handled the initial outbreak in one of the best ways to actually make it stick. There was a worldwide dust storm which infected everyone. A large fraction of the population succumbed to the infection and died or became “zombies” (more vampires really, they retained a lot of intelligence. The Will Smith movie really fucked the plot.). It’s one of the few ways to get past the problem of the various world militaries just curb stomping the initial zombie outbreak. Sure, there would be some confusion and some losses while people figured out the various rules for the zombies, but WWI is kinda instructive here. Massed charges into machine gun fire didn’t go well for the soldiers in the charge. As another historic example, the Banzai Charge employed by Imperial Japanese soldiers during WWII was not only suicidal by nature, it was worthless against a well armed, organized line. Yes, zombies might be more resilient and less prone to morale breaking, but they’d still be mowed down en masse. And that’s before we consider air strikes, artillery and napalm. A combined arms assault against a mass of zombies wouldn’t be pretty. Especially considering that zombies wouldn’t have the strategic thinking to attack supply lines and depots.

Zombie outbreaks are fun in media. I’m currently playing 7 Days to Die, again. And I’m having lots of fun. I also don’t spend too much time thinking about what the backstory might be. There’s zombies, and it’s my job to survive. That’s all the setup I need to enjoy the catharsis of zombie heads exploding in gore.