What percent of migraine headaches are caused by chronic viruses present in the body?

We see that migraine headaches are caused by chronic viruses approximately 80% of the time, and thus this represents the majority of cases. As you can imagine, production of this particular symptom is from the confluence of pathologic changes due to the presence of chronic viral infection and an immune response mounted to counter it causing local dysfunction as collateral damage. And that will give rise to symptoms in some individuals more than others as a function of genetic predisposition and the karmic history as well. This makes pinning down a confirmation of the cause more difficult and results in the complications you are dealing with. It creates a situation where there are large numbers of seemingly healthy individuals from whom chronic viruses can be detected and this makes it impossible to establish on a statistical basis the true cause and effect here, because other variables confound the picture and make drawing hard and fast conclusions impossible, looking at migraine sufferers as a whole.