Here is a more detailed article about this vagus nerve hypothesis on a ME/CFS research blog(hat-tip to this blog):
“One Theory To Explain Them All? The Vagus Nerve Infection Hypothesis for Chronic Fatigue Syndrome”
VanElzakker proposes that an infection triggers ME/CFS, but if his theory is right the most important thing about that infection is not what it is but where it is. That ‘where’ is the biggest nerve in the body; the vagus nerve – a ‘wandering nerve’ that stretches over much of our torso and sends its roots into most of the organs of the body.
The vagus nerve isn’t just any nerve; it’s the nervous system’s immune conduit to the brain. VE believes that an infection there doesn’t need to be large to cause havoc in the brain; it just needs to be present.
In some ways, vagus nerve appears, in fact, to be ripe for infection in ME/CFS. As it ‘wanders’ through the body it comes into contact with virus havens such as the esophagus, stomach, lungs and spleen, all of which have likely at one time or another harbored the herpesviruses (HHV6, HHV-5 [cytomegalovirus], HHV-4 [Epstein-Barr virus]) that have been thought to be associated with ME/CFS for decades.
Most humans carry several of these herpesviruses in latent form unless some stressor or biological event allows them to become reactivated.
VanElzakker believes that upon reactivation these viruses replicate and move outside the nerves where they run into glial cells that attempt to gobble them up. The glial cells perk up remarkably in the presence of viruses, releasing all manner of pro-inflammatory and neuroexcitatory compounds (proinflammatory cytokines [IL-1B, IL-6, TNF-a], glutamate, prostaglandins, nitric oxide and free radicals. ) - See more at: http://simmaronresearch.com/2013/12/one-theory-explain-vagus-nerve-infection-chronic-fatigue-syndrome/#comment-5430
I’ve read that the vagus nerve may constitute another brain.