Wendy, there are several possibilities but here is a highly likely one:

http://www.afip.org/ferrets/ECE/ECE.html

and there is more on this coronavirus in the FHL Archives.

BTW, for those who don't know either of these two things:
ECE has been molecularly characterized. There is a new coronavirus
being seen in ferrets which behaves and looks like the dry form of FIP
(feline infectious peritonitis) in cats. It was first identified in
Europe but has been found in several places in the U.S. beginning last
year.

Dry FIP develops slowly in cats without pronounced fluid accumulation.
Common symptoms include weight loss, anemia, fever, and depression.
Young cats may have thier growth stunted. Also:

BEGIN QUOTE
Other symptoms depend on the organs affected:
Increased water consumption and urination (kidneys)
Jaundice (liver)
Vomiting and/or diarrhea (pancreas)
Ocular inflammation, conjunctivitis, and blindness (eyes)
Brain inflammation, paralysis in the hind legs, weakness, shaking,
vertigo, seizures, and personality changes (central nervous system)
The affected organs often develop a characteristic pyogranulomatous
inflammation, in which the diseased tissue becomes thickened with an
accumulation of white blood cells. The only definitive way to diagnose
this form of FIP is by postmortem biopsy of the lesions.
END QUOTE
from
http://www.animalhealthchannel.com/fip/symptoms.shtml

http://ferrethealth.org/archive/YPG662

http://ferrethealth.org/archive/YPG394

Another problem seen too often is failure to look for the right
coccidia forms and failure to look at least 3 times in a week with
diarrhea.

http://ferrethealth.org/archive/YPG655

http://ferrethealth.org/archive/YPG616

http://ferrethealth.org/archive/YPG592

I suggest printing those references out for your vet and yourself.

Sukie (not a vet)
Current FHL address:
http://groups.yahoo.com/group/ferrethealth
People can join there or can send a blank mail to the automated
joining address:
[log in to unmask]
and then follow the directions.
(The second is recommended for those having problems with Yahoogroups
web settings, and afterward send a blank mail from your subscribed
address to
[log in to unmask]
to get the digest instead of individual mails. )
Recommended ferret health links:
http://pets.groups.yahoo.com/group/ferrethealth/
http://ferrethealth.org/archive/
http://www.afip.org/ferrets/index.html
http://www.miamiferret.org/fhc/
http://www.ferretcongress.org/
http://www.trifl.org/index.shtml

[Posted in FML 5503]