There are so many links to issues with NO, it makes me wonder if low NO is because of a virus using up all of the arginine, etc. Symptoms would be caused either from low NO or from NO feeding viral replication. Increasing NO may help some because it's depleted by the virus, but eventually it begins to feed the virus again, unless you are sufficiently suppressing it via another pathway. I have been experimenting with PDE5 inhibitors. They almost always exacerbate my symptoms, and I get the day or two after "hang over." It seems to increase my NO / arginine levels, which may be feeding EBV/HHV6. My HHV6 titers were elevated when checked. Using mice models, mice with lower NO levels seemed to starve the influenza virus: https://www.ncbi.nlm.nih.gov/pubmed/23420903 Could this explain the NO connection?