For those of you who are interested in the status of KHV reports in Japan at the end of 2018, here's the current info (see below).  This is from a Japanese Nishikigoi website.

First of all, thank you very much for your cooperation and understanding of our activities.
We have been working with the governor’s guidance on preventing the occurrence of widespread disease in the Niigata region. In spite of our efforts, KHV was detected at some breeders in 2018 that unfortunately were shipped. On behalf of all Niigata breeders, we deeply apologize for any inconvenience this has caused you.
We would like to share the information of each breeder’s KHV situation. The information will be updated from time to time, so please keep checking the status.

Tazawa Koi Farm (Uonuma City)
June – Received positive KHV result (Inspected by Kento Food and Environment Analysis Center)
-> Shipping suspension
To prevent spread of KHV, euthanized all Koi which possibly infected.
August – Confirmed positive KHV result (Inspected by National Research Institute of Aquaculture)
-> Instruction of no movement of Koi
All Koi in mud-pond was negative result (Inspected by Niigata Prefectural Inland Water Fisheries Experiment Station)
Mr. Tazawa is elderly so he will euthanize all his Koi and close his farm.

N.N.B.C. (Nagaoka City)
Nov 25th – Received positive KHV result (Inspected by Kento Food and Environment Analysis Center)
-> Shipping suspension
Nov 28th – Confirmed positive KHV result (Inspected by National Research Institute of Aquaculture)
-> Instruction of no movement for all green house koi
(KHV positive result was found in green house pond)
Nov 30th – Euthanized and sterilized
In his green house, some ponds are positive and others are negative. However, to prevent spreading KHV, all Koi in the same green house were euthanized. Sterilization of affected green house has been completed.
His other facility’s ponds were found to be negative.  As precaution, those ponds are being heated to bring up the temperature and will be tested again shortly.
Keep instruction of no movement of Koi.

Hoshikin Koi Farm (Ojiya City)
Dec 14th – Received positive KHV result (Inspected by Niigata Prefectural Inland Water Fisheries Experiment Station)
-> 1 out of 5 green houses, of which 1 pond out of 10 ponds was positive result.
Shipping suspended. Remaining 4 green houses were negative.
Dec 17th – Confirmed positive KHV result (Inspected by National Research Institute of Aquaculture)
-> Instruction of no movement for all green house Koi
Dec 19th – 9 out of 10 ponds were negative
-> Keep suspension of shipping.
Dec 27th – Euthanized and sterilized
-> Following the governor’s instruction, euthanized all koi in the entire green house which got positive result. Also sterilizing green house has been completed.
The remaining other 4 green houses which were negative are being heated to bring the ponds’ water temperature up and are now under observation. The farm will have another inspection shortly.
Keep instruction of no movement of Koi.

Yamacho Koi Farm (Nagaoka City)
Dec 17th – Received positive KHV result (Inspected by Niigata Prefectural Inland Water Fisheries Experiment Station)
-> 1 out of 3 green houses was positive result.
Shipping suspended.
Dec 19th – Confirmed positive KHV result (Inspected by National Research Institute of Aquaculture)
-> Instruction of no movement for all green house Koi
Dec 20th – Euthanized and sterilized
-> There was a movement of Koi in each of his green houses, following the governor’s instruction, euthanized all koi in the 3 green houses. Also sterilizing green house is completed.

To offer healthy koi to our customers and hobbyists, all Niigata breeders are committed to enact a stricter inspection system and protocol to ensure health and safety of Nishikigoi.  To achieve our goal, we are forming the ‘Nishikigoi Guideline Committee’ that will formalize the protocols in preventing spread of fisheries diseases.  Thank you for your understanding as we work to ensure Nishikigoi’s future.