Other than that I need someone to explain to me why there are so many zombies.
Presumably during the initial infection the disease (or cause or whatever) was transmitted in other ways inaddition to "bite". That's why the plague starts everywhere on the planet etc.
People, if they are strongly subseptible, turn without being bitten. Of course the "survivors" don't have any one like that in their number, just to live that long you have to be resistant to the plague.
Presumably this means that some people would NOT turn if bitten, just like some people don't die from having AIDS.
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No one is stronger than...ahem.