When I was at Soules Gardens, the owner told me more about the HVX virus infecting hostas. I had come across some information on this recently, so I had at least heard of it. Click here for more information on this virus. They include pictures to help identify hosta plants that are infected. Essentially, there is no cure. If you aren't sure if any of your hosta have the virus, they recommend cleaning your cutting tools thoroughly with bleach as you move from hosta to hosta trimming up old flowers and damaged leaves.
And you should avoid buying a hosta that you think might be infected, or where the staff do not know of the disease. The most common place to find infected hostas is at "big box" garden center departments who buy from wholesale growers who either don't know about the virus or don't care if the plants they are selling are infected.
(The hosta pictured here are in my sister's garden. She and her husband have a lot of shade and love hostas.)