Authorities are always depicted as idiots in zombie apocalypses, for no good reason except “so the plot can happen” (to quote the Critical Drinker).
What really bothers me about most zombie apocalypse novels is the irrational way that the authorities respond to the zombie apocalypse. The authorities on every continent and every country decide that the proper way to respond to a highly contagious and uniformly lethal disease is to herd together everyone who doesn’t seem to be infected.
Sometimes the author mentions the problems of water supply, sanitation, food, and protection against the hordes of zombies that would naturally be attracted to the large supply of victims, but I think the more obvious problem is that there is no real way to know who is infected. When you collect up thousands or tens of thousands of “uninfected”, you will almost certainly bring in some who are infected. And now you have set up an unparallelled zombie-breeding pen.
I can’t imagine why anyone would think this would be the response of the authorities. It wasn’t even the response to Ebola, where there’s an actual blood test for infection; why would it be the response to a disease that is so new and moving so fast that there is no time to develop a test?
In the military, you often want to consolidate your forces so you can defeat the enemy wholesale instead of them defeating you retail, but zombies aren’t enemy forces. By telling people to shelter in place and keeping them separated from each other, you prevent rapid contagion and ensure that the zombies that do arise are also separated instead of forming massive groups. Then you defeat them retail because you are smart enough to plan your assaults, and they aren’t.
Also, of course, if you don’t collect thousands or tens of thousands together, you can provide for sanitation and water, at least, by protecting the people who maintain the utilities. As I’ve pointed out before, there are a lot of ways that people can protect themselves against zombies while sheltering in place, ways which are not available when you herd thousands together. Food will be a problem but it takes a while for people to starve. To be blunt, they can go hungry until you get the zombie problem under control.