Hi Lane,
I really Do not want to go into much of it here because of the lack of info that is provided. What I mean is there are still many heated debates on this issue.
Many high up that study Viral infections do not agree on the same things said or found.
Here is a good link for You to read. Some of these Viral's have been found in discus.
HTH
TakeCare,
Cary Gld!
http://www.afip.org/CLDavis/GrossCourse01/fish.htm