I missed the original post, but it seems someone would like to know why some
viruses are specific to certain species and some affect more than one
species.  There are several factors contributing to virus specificity.
 
First, you need to know that there are millions of kinds of viruses.  A
virus is an extremely simple organism.  You could almost think of it as a
biological machine, and not a living thing at all.  Most viruses have a
genome, which is usually quite small, encased in a membrane of some sort,
and that's it.  The usual route of attack is adherence to the targetted
cell, transport into the cell, and hijacking of the host cell's DNA
transcription and translation machinery to reproduce.
 
Now a virus can affect many different kinds of cells.  The flu virus attacks
your gut.  Owie.  HIV goes after white blood cells.  I wish I could remember
the specifics of Corona and other viruses.  However, in general, viruses are
very specific to their targets.  So specific, in fact, that while dogs and
gnus and alligators may have the same kind of cells, these cells will be
different enough from the ideal species target cell that they are not
susceptible.  For example, your dog can't get HIV from you.  His white blood
cells (remember I'm not a vet so I really don't know anything about dog
immunology :) look/feel/taste different than human white blood cells.  HIV
probably can't even bind to the surface of these white cells.
 
On the other hand, ferrets can get the flu, so there must be enough
similarity between the biochemical characteristics of human and ferret tummy
cells to allow the virus to switch between the two.
 
If anyone is interested, I can dig up my old virology text and give you more
specific examples.  However, the whole point is that viruses are very
diverse, and by their nature quite specific.  Otherwise they wouldn't be
able to fool the host into making more viruses.  (If the neighbor's ferret
walked into your house would you clip his nails?  Well...maybe, but--)
There's no way to know if ferrets are susceptible to a certain virus without
doing the appropriate scientific studies.  You can't assume they are or are
not susceptible by extrapolation from a different virus.  I hope that helps.
 
I guess the best way to answer this question is to take a few years of
college biology, biochemistry, and virology.  Failing that, it's sorta hard
to understand.
 
On ferrets and babies: There are many rumors, and I would say they are all
untrue.  You know your ferrets better than anyone else.  Why should you
listen to some idiot off the street who thinks that ferrets kill babies?  I
had some jerk tell me this a while back and I just couldn't believe it.  If
you have any doubt, take your ferret to a house where a baby lives.  He will
probably be much more interested in the diaper bag.  Ours always are.
 
-Catherine Shaffer
[Posted in FML issue 1636]