I am writing this in the hope it is helpful for some of you.
My headaches, and other symptoms were most definitely caused by a virus. Here goes.
I was an exceedingly healthy and active child and teen. At age 15, I became very ill with what we thought at the time was an acute but typical flu-type illness. High fever, aches, chills, weakness, headaches. For a week or so, my mom would wake me up to hydrate me and try to get some broth into me and then I would pass out again. I was the only one in the family who got sick, so not contagious. I grew up in the woods in New Jersey in the middle of mosquito country. The year was 1975. I recently found out there was an outbreak of a particularly dangerous mosquito borne disease in New Jersey in 1975 called Arboviral Encephalitis, aka Eastern Equine Encephalitis, St. Louis Encephalitis, Western Equine Encephalitis, La Crosse Encephalitis and Powassan Encephalitis. "Many people who survive EEE develop residual, long-term, mild to severe neurologic deficits." Coincidentally, this past summer there was another outbreak of this in several US states. Here's more info on it for anyone interested. https://www.nj.gov/health/cd/documents/chapters/eee_ch.pdf
The first night of the 'flu' I got a massive headache, like an ice pick behind my right eye (uh huh, yeah, I know right?) and yup, you guessed it, I have gotten them ever since. In my case, I have chronic headaches that occur daily at or around the same time; late afternoon, evening or night. The times are consistent every day but they tend to migrate over periods of months. My right eye tears like mad, my right sinus swells shut, my neck gets stiff, etc.
After the acute phase of the flu subsided and my temperature went back to normal (low normal actually), the symptoms never went away. In addition to the daily headaches, I developed massive chronic fatigue, intense brain fog, fibromyalgia, food sensitivities, etc, etc. My life as I had known it ended that day. I had to modify my high school schedule so that I could take the classes I legally needed to graduate in the mornings, be home by noon, crawl into bed, wake up at 7 to eat and do homework and go back to bed. My greatest accomplishments will always be getting a college degree in that condition and raising two healthy, well-adjusted young men (neither of whom get headaches).
Many years later I got a dangerous intestinal bacterial infection (C-dificil) that landed me in the hospital for 4 days on massive doses of IV antibiotics. This was a turning point in my life and went a long way to eradicating the fatigue, brain fog and fibromyalgia, but not the headaches. The headaches remained consistent but the other symptoms could be kept largely under control as long as I don't move much or exert myself (I am oversimplifying for the sake of brevity).
As I mentioned, I am writing this in the hope it is helpful for some of you. Feel free to reach out if you have questions or if I can help in any way.