Finally, none of the behavioral characteristics typically associated with contagious disease, such as intravenous drug use, exposure to animals, occupational or travel history, or sexual behavior, have been associated with CFS in case-control studies. It therefore seems unlikely that CFS is a transmissible disease. Nevertheless, the lack of evidence for clustering of CFS, the absence of associations between specific behavioral characteristics and CFS, and the failure to detect evidence of infection more commonly in CFS patients than in controls do not rule out the possibility that infectious agents are involved in or reflect the development of this illness. This knowledge is required to facilitate communication between physicians and patients, to evaluate possible new treatments, and to address insurance and disability issues. Some patients recover to the point that they can resume work and other activities, but continue to experience various or periodic CFS symptoms.
Some patients recover completely with time, and some grow progressively worse.
CFS often follows a cyclical course, alternating between periods of illness and relative well being. No characteristics were identified that made one patient more likely to recover than another. At illness onset, the most commonly reported CFS symptoms were sore throat, fever, muscle pain, and muscle weakness. As the illness progressed, muscle pain and forgetfulness increased and the reporting of depression decreased. All information presented in these pages and all items available for download are for public use.