In a way, a zombie invasion is just a fantasy step beyond something much more realistic.
In 1859, 12 wild rabbits were brought to Australia by a man who liked to hunt rabbits. By 1886 their descendents were colonizing new areas of southeastern Australia at the rate of 66 miles a year in all directions. By 1907 the rabbits had reached both the west and the east coasts of Australia, roughly the distance between California and New York. Nothing could stop the plague of rabbits.
The rabbits were eating much of the sparse vegetation that supported Australia’s huge sheep and cattle industry, and the graziers were suffering enormous financial losses.
The only solution was biological control. After much testing, government biologists introduced a mosquito-borne virus called myxomatosis, that was only lethal to rabbits.
The disease did indeed take hold in 1950, and by 1952 it had produced a nationwide epidemic in the rabbit population. The mortality rate reached an estimated 98% of the rabbits. But the remainder were immune and have since replenished their overpopulated numbers.
Were such a disease, likely an influenza, to strike the human population with high mortality, the world could lose billions of people. And not evenly distributed. The third and fourth world would likely have far greater losses.
Yet this is the opposite of a zombie invasion, for instead of zombies everywhere, large habitable areas would seem to have few if any people.
If you take his list of various groups, you have to ask yourself how different their responses would be to this scenario, instead of the zombie one.
An Aussie fellow told me, after I showed him my AKUBRA hat, that approximately 200 rabbits are used to provide the felt for just one hat(I’ve got four). He said that they are vermin, pests and good riddance.
zombie apocolypse is fun, because it is silly and cathartic. The thought of a Black Death scale epidemic is horrifying because it is realistic. Civil society, infrastructure and transportation would collapse. More people would die of starvation and anarchy than the disease.