Chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is a complex medical condition, characterized by long-term fatigue and other symptoms. These symptoms are to such a degree that they limit a person's ability to carry out ordinary daily activities. CFS may also be referred to as systemic exertion intolerance disease (SEID), myalgic encephalomyelitis (ME), post-viral fatigue syndrome (PVFS), chronic fatigue immune dysfunction syndrome (CFIDS), or several other terms.Quality of life of persons with CFS can be extremely compromised.

Biological, genetic, infectious, and psychological mechanisms have been proposed, but the cause is not understood. The fatigue of CFS is not due to ongoing exertion, is not much relieved by rest, and is not due to any other medical condition. Diagnosis is based on a patient's signs and symptoms.

There is agreement that CFS has a negative effect on health, happiness and productivity but there is also controversy over many aspects of the disorder. Physicians, researchers and patient advocates promote different names and diagnostic criteria, while evidence for proposed causes and treatments is often contradictory or of low quality.