Chronic fatigue syndrome may have a post-viral infection origin
Physician here. Imo CFS is best understood as the endpoint of an evolution within the nervous system that is increasingly called "central sensitization syndrome."  (CSS) This syndrome is caused by a chronic dissociative or avoidant stress response, usually having it's origin in early childhood adversity. Prior to developing CFS, most individuals have other manifestations of CSS, such as IBS, chronic pain, TMD, etc. Every new stress, be it a viral syndrome, a grief event, a difficult move of house, what-have-you, can cause CSS to further evolve, eventually arriving at CFS. The average CFSer has 5 other CSS syndromes. Treatment is pacing and mindfulness. This treats the underlying issue of chronic avoidance/dissociation. See cfsselfhelp.org.