I like the idea that Arthur tossed out... If we are going with the idea that the Zombie outbreak is man made then Ground Zero would naturally be the site of the lab or instalation that was doing the Z research. They'd know about how the zombies work and any weaknesses and the ability to create countermeasures to exploit those weaknesses.

That being said maybe the effects that "Don't call me Vic" and Peggs were experiencing was due to an area deniability device such as Arthurs subsonic device idea or a microwave device like the Army and some police departments have, or it could be a device that KC made for the plotline of the story. This would have the benifit of keeping the Zombies away and also keeping any survivors away from the possible facility.
It would also explain why other animals are no where to be seen in the area as it would affect them as well. And so far in the story we haven't seen if animals are affected by the Z "virus" (or whatever it is), which also piqued my thoughts on an area deniability device.

http://en.wikipedia.org/wiki/Long_Range_Acoustic_Device