Lack of energy is something that significantly impacts quality of life. Some people are tired every day, all day, and that's particularly frustrating when medical screening is normal. There are many possible causes of fatigue, and the idea of infection is often brought up, especially viruses such as Epstein Barr Virus, Cytomegalovirus, and others. Along those lines, a recent article in the Journal of Medical Virology
reflects a study done by researchers at the University of South Florida in which the case is made that yet another virus seems to be correlated to Chronic Fatigue Syndrome. The virus is Human Herpesvirus 6 (HHV6), which is the one that causes roseola in infants. Not only is the virus extremely common (over 95% of the population is infected by the virus at age 3), it is unique among herpes viruses in that it can be inherited (it's DNA can integrate itself into chromosomal telomeres).
As with any virus, the extent to which it causes symptoms will relate directly to the health of the immune system. The health of the immune system will relate of course to factors such as stress level, diet, sleep quality, environmental toxin exposure, and nutrient deficiency (especially vitamin D).
To read an article in Science Daily discussing the virus, and it's relationship to Chronic Fatigue Syndrome, you can click on this link: