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.