Which rapid switching are you referring to? Do you mean the switch between healthy and getting ME/CFS?
No, I meant the temporary remissions. I've had the baseline symptoms for years, then triggered temporary remission within hours, felt totally healthy again and bouncing with energy, then some more hours later, abruptly switched back to baseline ME symptoms. To me that doesn't match viral population change. I think it's more likely a switch in something, maybe RNA transcription of some protein, with a cascade reaction that affects the whole body. My guess is that it's in some system that controls major systems, perhaps a hormone gland. The immune system may have the means for switching into an activated state body-wide, but I'm not sure if it has that quick or general of a 'all immune cells return to normal function' function.
The temporary remissions have also been triggered by different drugs or chemicals, which again doesn't really fit a viral cause for ME symptoms. I very much doubt that T2, prednisone, and cuminaldehyde are all going to have similar abrupt on/off effects on a chronic viral infection.