The only fish affected by KHV (Koi Herpes Virus) are Koi, Carp, and goldfish can be carriers, but it will not kill the goldfish, and they rarely show signs.
KHV is horrible. Once you get it, say goodbye to everything. You need to basically kill off your stock, and start over with either bleaching everything or buying all new materials (nets, liners, filters etc...) It can, and will wipe you out.
Many people have been trying to find a way to cure it, restrain it, and also show for it with quarantine. There is a distinctive 2 month QT that's been created by USAKoi, where they play with water temps etc...
I just started doing that with my koi this year, as well as testing every 5 fish out of my stock. It's $20 for blood testing from the University of GA.
KHV normally will show when water temps reach 70's and up. Fish can only be infected when another fish is shedding the KHV virus.
There is not much known of KHV, but the best thing you can do is get them tested.