Anxiety can be a normal healthy response to something that scares us or stresses us out like, I don't know, tigers. The unpleasant emotions and sensations it gives us make us do something about it, like run away! Unfortunately the world we live in has created situations that can't easily be fought or escaped -- like taxes -- and for some people the anxiety happens without any clear reason.
In order to raise awareness of disaster situations and encourage people to prepare for them the Centre for Disease Control created a fictional zombie apocalypse. It ended up being the most visited area of their website.
As the director of CDC said:
"If you are generally well equipped to deal with a zombie apocalypse you will be prepared for a hurricane, pandemic, earthquake, or terrorist attack."
But be careful how far you take the simulation. A man in Miami decided he would test how prepared his neighbours were by wandering the streets covered in fake blood and pretending to be a zombie. The prank backfired when he found a group who responded by chasing him and threatening him with a gun. (see the vid on youtube).