Chronic fatigue syndrome (CFS) is the most common name given to a variably debilitating disorder or disorders generally defined by persistent fatigue unrelated to exertion and not substantially relieved by rest, and accompanied by the presence of other specific symptoms for a minimum of six months.The disorder may also be referred to as post-viral fatigue syndrome (PVFS, when the condition arises following a flu-like illness), myalgic encephalomyelitis (ME), or several other terms. The etiology (cause or origin) of CFS is currently unknown and there is no diagnostic laboratory test or biomarker.
