All koi are routiinely tested for KHV here in th UK Sharon I cant say about where yours came from?
SVC normally comes about by keeping wild carp in with pet koi and is a spring virus as in its name Spring Viraemia of Carp and as such shouldnt be a worry to you .
KHV is a major problem in the Pacific and many other Far eastern countries Indoneasia, Malaisia, and many other countries where there are no such checks, (as a South African koi keeping friend found to his cost when his entire pond was whiped out).
But as long as the company you bought this koi from test then thats a garentee .
Here in the UK both these viruses are defra notifiable i;e Government Farm and Fisheries but here in the UK the koi dealerships have formed an assocciation which garentee's hat all koi are checked for KHV, we do however still get it.
We had an outbreak in Plymouth last year in my friends Uncles pond however these koi were bought via eBay where there is no such garentees or controls, such a shame too as it whiped out a long held koi collection bought over many years..
As Koiguy has said you sometimes get koi who wont eat but eventually start , it may be that the water where your koi came from was either Hard of soft water and the water where you live is the opposite i;e the koi isnt used to yours just yet .
Weve had this , I bought one koi from Yeovil Somerset brought it back to Plymouth and it instantly shed its colour , the problem .....well we found out it was the water in Somerset from the area we bought it from, why ???....it turned out that they had hard water we had soft .and it basically didnt like our water..
So instead of a yellow and white koi we ended up with a white koi permanently , it didnt eat for a week and had us just as worried as you are now.
Did you say you have a microscope ?... do you know how to take a scrape I think I remember explaining things to you a while back ?
If so do a scrape and elliminate Parasites from the equasion or if you find them treat the koi then it will at least give you a peace of mind that you are doing the best for this koi .
All in all try not to worry ...
Dave
PS cant wait to see the photo which if you use the full editor will give you access to your photo's to post them