KHV- Koi Herpes Virus....the bad thing is that it Does NOT kill all koi....some Koi will never get the disease but, they can be carriers of the virus....and then infect all of your koi and kill them...It can lay dormant for years and then come out when the koi are stressed...there are tests for it but, as long as they are not actively shedding the virus they still come up negative....and then when the koi gets stressed and starts shedding the virus ---it will kill all of the other koi....and it seems to be popping up more and more....I haven't brought any new koi onto our place in 4 years because I don't want to take any chances with the ones I have...and since I really have no place off and away from my other koi and I've got soo much foot traffic thru here---I just won't take that risk...so with no cure, no real definite tests available yet....you really need to make sure to qt,qt,and qt....and then when you think they are safe qt some more .......
Lawanna