Although for research purposes the clinical definition of the chronic fatigue syndrome (CFS) is well established, many aspects of this illness such as its etiology, pathogenesis, and treatment are still unknown. Even the clinical definition is subject to controversy, and although much effort has been expended in the investigation of the clinical aspects of the syndrome, little is known about its epidemiology.
This article considers a cohort of 14 cases that meet the criteria of CFS.The signs and symptoms of CFS in these cases manifested during, or shortly after, a trip to a tropical country.These signs and symptoms appeared to be related to cytomegalovirus (MV) or Epstein-Barr virus infection (EBV).
You can read the full article here: http://jtm.oxfordjournals.org/content/jtm/2/1/41.full.pdf
Source: Gascón J, Marcos T, Vidal J, Garcia-Forcada A, Corachán M. Cytomegalovirus and Epstein-Barr Virus Infection as a Cause of Chronic Fatigue Syndrome in Travelers to Tropical Countries. J Travel Med. 1995 Mar 1;2(1):41-44. http://www.ncbi.nlm.nih.gov/pubmed/9815359