My doc uses the lymphocyte subset test, specifically looking at cd8 t-cells which are normally high in ebv/cmv infections. Famvir has helped me to bring them back down to normal but my last test while still on famvir, my cd8 numbers went slightly high above the normal range, maybe viruses reactivating again??
I will say that antivirals have helped me but they arent a cure, i think there is something else underlying in cfs, but treating these infections will help you though, so go for it.
cheers!!!