If after Z-day then a silent form of communication using body language may need to be in place. My suggestion is that a color coordination system. including a way to tell of current stability in say a camp.
RED - Alone with supplies.
BLUE - Group with supplies.
BROWN - Searching for survivors have camp level 1(5-10 survivors a years worth of supplies or less).
BLACK - Searching for survivors have camp level 2(11-25 survivors two years of supplies and moderate defenses).
DARK GREY - Searching for survivors have camp level 3(26+ survivors 3-5 years of supplies or farming in place and moderately sever to sever defenses or a civilization infection free).
PURPLE - Needing refuge no or little supplies and alone.
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