Chronic fatigue syndrome

Classification and terminology

Many names for the illness have been proposed. The most commonly used are myalgic encephalomyelitis, chronic fatigue syndrome, and the combined umbrella term myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Agreement on a name has been difficult because the cause and pathology remain unknown. In the WHO's recent classification, the ICD-11, chronic fatigue syndrome and myalgic encephalomyelitis are named under post-viral fatigue syndrome. The term post-infectious fatigue syndrome was initially proposed as a subset of "chronic fatigue syndrome" with a documented triggering infection, but is also used as a synonym of ME/CFS, or for a broader set of fatigue conditions after infection.