Office of Research on Women's Health (ORWH)
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), sometimes referred to as myalgic encephalomyelitis (ME) or chronic fatigue syndrome (CFS), is a debilitating disease that lacks a universally accepted case definition, etiological agent, diagnosis, or treatment.
The disease is characterized by six months of incapacitating fatigue experienced as profound exhaustion and extremely poor stamina, and problems with concentration and short-term memory. It is sometimes preceded by flu-like symptoms followed by pain in the joints and muscles, unrefreshing sleep, tender lymph nodes, sore throat, and headache. A distinctive characteristic of the illness is post-exertion malaise, a worsening of symptoms following physical or mental exertion occurring within 12-48 hours of the exertion and requiring an extended recovery period.
Roughly 17 million people worldwide (one to four million in the United States) are estimated to have ME/CFS. ME/CFS strikes people of all ages and racial, ethnic and socioeconomic groups, and is diagnosed two to four times more often in women.