I thought it'd be intersting to find this out. I've had great sucess with them because my only infections are EBV and HHV6. For EBV, I took Valtrex and Famvir. I felt terrible for the first month--could not sleep, brain fog, photo sensitivity, felt like I was on drugs (i.e. floaty and disconnected), dizziness. These were all symtpoms that I already had that got much worse for awhile until I broke through it and felt almost normal for like 18 months. I relapsed with HHV6and now I take Valcyte. I have felt terrible for the 2 months I have been taking it. It has amplified all of my other cerebral symptoms. I have a terrible headaches, photosensitivity, insomnia, and my eyes are dilated. This "die-off" is very long lasting. However, I quit taking it for 4 days after one month, and I felt better than I had before I started taking it (while on vacation), so I knew it was working, and started back on it after vacation. Hopefully, this valcyte will knock these viruses out.