Diana,
 
I think I can speak for many......yes, you can spread colds/flu back and
forth between you and your ferrets.  About 4 years ago I caught the old
fashioned flu, you know the fever, aches, pains, headaches and etc., from
my son's two ferrets who caught it from his girlfriend.  Then my ferrets
and I caught it.  My ferrets were put on amoxicillian and lots of liquid,
and came through it fine.  Frankly, I thought I was gonna die, but I
survived also, though for a while had my doubts.
 
If it isn't already too late, it is best to quarantine your "business",
no sense in putting them through the misery, but if they have already
contacted carriers, you may just have to treat all of them.  Make sure they
have lots of liquids to prevent dehydration, and if there is vomiting and
diarhea, my vet prescribed the amoxicillian and pepto bismol, though some
on this list do not like the pepto (and the ferrets hate it).  But it
worked for us!
 
Good luck with your "business", I hope it doesn't get out of hand with
the flu.
 
mjo and the zoo (Lady Star, Topanga, Ragine, Bilbo, Frodo, Frito,
Pepper, & Caesar and the dogs Garth and Darwin......r.i.p.  PHANTOM,
Nipper, EZ, Lightning, Cleo, & Duke)
 
[P.S.]
Diana,
 
Something I forgot to add that is very important, do contact your vet.
Let him/her give you professional advise in this matter as well as any
other medical problems that come up.
[Posted in FML issue 3205]