Vulnerability Development: Infected jpeg files?

[<rginski () co pinellas fl us>]

Mailer: SecurityFocus

Is it possible for a virus to infect a jpeg (*.jpg) file, 
then the jpg file to infect other files?...without 
changing the files characteristics? In other words, a 
jpeg file (file.jpg) is infected and it 
remains "infected_file.jpg". It is possible for a file type 
as jpeg to have a payload or cause damage although 
it's just being viewed? Perhaps something like 
steganagraphy...except embedding vbs (or 
something) causing infection by way of the viewer? I 
guess another way of asking the question is:

Is it possible to get infected by just viewing jpeg files?

I realize that's a "wide open question" I just don't 
know how else to explain myself. Thanks in advance 
for your patience and help.