Thanks for the replies, I am referring him to the forum.
I have seen many places with loads of fish which appeared quite healthy, only to discover that there were in fact KHV and an outbreak followed.
At the end of the day, one should only buy from reputable dealers who quarantine properly and who can provide details of where the fish comes from, and what tests has been done to ensure that the stock has no KHV. Insist on a KHV free certificate, especially if the fish were imported and enquire about the quarantine procedures followed. If fish just arrived and already for sale, stay away.
Be informed by browsing forums as Cliff said, and if there are ANY indication of health problems at the facility, stay away.
Stay away from the fly by nights and stay away from dealers who keep KHV survivors, there are quite a few.