A danger zone (not the kenny loggins type) which causes any entrants hygiene to deteriorate rapidly and then contract various STDs. Condition worsens exponentially depending on a few things:
A) How long said person is in said zone.
B) If said person is naked while in said zone.
C) If a person touches anything while in said zone.

Interestingly enough, if a person is a permanent resident of the quarantine area they develop an immunity to the various ailments which can afflict mere mortals.

When you eat dirt for the first time and leave your family to build a shack in the woods