I had normal titers for all herpes viruses (no active infections) when I took IV ganciclovir. This is before Valcyte came out; Valcyte is a prodrug for ganciclovir (i.e., it metabolizes into it). I took the ganciclovir based on a positive stealth virus test by Dr. John Martin. I was on the ganciclovir for seven weeks, and it did wonders for me; by the end of treatment, I thought I was going to be able to go back to work soon. No such luck. But three months later, Valcyte was approved by the FDA, and I immediately started taking it. I had headaches and a low-grade fever constantly from the beginning of my illness (actually, my final relapse); they went away two and a half years later during the ganciclovir treatment and stayed away while I was on Valcyte. Whenever I went off the Valcyte, they came back, though. Finally, after five years on Valcyte, I was able to go off it without the headaches or fever (except very occasionally), and with no other negative side effects. Virus levels can be very high in the CSF even when they're low in the blood, and I think that's what happened to me - hence the headaches. I think it just took five years to wipe out a virus in my brain, which as I have explained in another thread, I have reason to believe was herpes zoster. Valcyte crosses the BBB very well, and is very effective against zoster. But you can have a very active case of a virus in your CSF that will never show up on standard blood tests. In my experience with ganciclovir, I also noticed that it seemed to have immune modulating properties, based on the way my recovery progressed. My doctor thought that was very possible for the same reasons I did. Then, six weeks after the ganciclovir treatment ended, my immune system crashed, and I started getting various unusual (non-herpes) viral growths. My doctor said he hadn't seen an immune system failure like that outside of end-stage AIDS patients. So he brought in a couple of top infectious disease docs, and they took one look at me and decided I had HIV. They did all sorts of tests - HIV-1, HIV-2, and a few nonstandard HIV tests. Everything came out negative; this didn't surprise me, as I knew I didn't have HIV. My CBC was also basically normal, implying normal T cell counts. So based on my experience with the ganciclovir (which I could no longer afford), I told my doctor that I thought when Valcyte became available, I could make the viral growth go away. My doctor, of course, was skeptical, and I can't blame him. But sure enough, within a week of when I started the Valcyte, the viral growth quickly started to disappear, amazing my doctor. Yet while it was still disappearing, a growth of a different strain of the same virus appeared elsewhere on my body and began growing rapidly, as if my immune system weren't there. My doctor happened to run into Dr. Anthony Komaroff at the time, and told him all about this. Dr. Komaroff said he had never heard of such a thing. Meanwhile, I figured that maybe I had to pulse the Valcyte to get rid of the second growth (which was by now already scheduled for surgery). So I went off the Valcyte for two weeks, went back on it, and sure enough, the second growth rapidly started to disappear, and I canceled the surgery. Both growths soon disappeared entirely. So did a large wart that I had had on my left index finger for 40 years - you can't even tell where it was now. So Valcyte is indeed a powerful immune system modulator, at least in my experience, but like other immune system modulators, it needs to be pulsed for best effect.