ME/CFS nomenclatures
ME/CFS does not have a potentially definitive name that is free of controversy.  Many names are currently used to refer to it, and many more have been used in the past to describe it or similar conditions.

# Current nomenclatures

## Systemic exertion intolerance disease
The Institute of Medicine has recommended the new name, "Systemic Exertion Intolerance Disease".

## Myalgic encephalomyelitis
Myalgic encephalomyelitis or ME translates to "inflammation of the brain and spinal cord with muscle pain" and first appeared as "benign myalgic encephalomyelitis" in a Lancet editorial by Sir Donald Acheson in 1956. In a 1959 review he referred to several older reports that appeared to describe a similar syndrome. The neurologist Lord Brain included ME in the 1962 sixth edition of his textbook of neurology,  A 1978 British Medical Journal article stated the Royal Society of Medicine conference to discuss the illness during that year clearly agreed Myalgic Encephalomyelitis was a distinct name for the disease. The article also stated the previous word (benign) used with ME was rejected as unsatisfactory and misleading because the condition may be devastating to the patient. In 1988 both the UK Department of Health and Social Services and the British Medical Association officially recognized it as a legitimate and potentially distressing disorder. Opponents of the term ME state that there is no objective evidence of inflammation. In some patients diagnosed with CFS (e.g. the case of Sophia Mirza), central nervous system inflammation has been documented. Many patients, and some research and medical professionals in the United Kingdom and Canada, use this term in preference to or in conjunction with CFS (ME/CFS or CFS/ME). The international association of researchers and clinicians is named IACFS/ME.

## Myalgic encephalopathy
Myalgic encephalopathy, similar to the above, with "pathy" referring to unspecified pathology rather than inflammation; this term has some support in the UK and US.

## Chronic fatigue syndrome
Chronic fatigue syndrome (CFS) was proposed in 1988 by researchers from the U.S. Centers for Disease Control and Prevention (CDC) to replace the name chronic Epstein-Barr virus syndrome when they published an initial case definition for research of the illness after investigating the 1984 Lake Tahoe ME epidemic. CFS is used increasingly over other designations, particularly in the United States. Many patients and clinicians perceive the term as trivializing, and as the 1994 Fukuda paper itself cedes, stigmatizing, which led to a movement in the United States to change the name and definition. Eighty-five percent of respondents to a 1997 survey conducted by the Chronic Fatigue Immune Dysfunction Syndrome Association of America wanted the name changed. The CFS Coordinating Committee (CFSCC) of the U.S. Department of Health and Human Services formed a name change workgroup in 2000. Terms were recommended which implied specific underlying etiologies or pathologic processes, but work was shelved in December 2003 when the successor CFS Advisory Committee (CFSAC) decided a name change would be too disruptive at that time.

## Chronic fatigue immune dysfunction syndrome (CFIDS)
Many patients and advocacy groups in the USA use the term CFIDS, in an attempt to reduce the psychiatric stigma attached to "chronic fatigue," as well as the public perception of CFS as a psychiatric syndrome. The term also calls attention to the immune dysfunction in patients which research suggests is an integral part of the illness.

## Post-viral fatigue syndrome (PVFS)
This is a related disorder. According to ME researcher, Dr. Melvin Ramsay, "The crucial differentiation between ME and other forms of post-viral fatigue syndrome lies in the striking variability of the symptoms not only in the course of a day but often within the hour.

## Low Natural Killer Syndrome (LNKS)
This term reflected research on patients showing diminished in-vitro natural killer cell activity in a small 1987 study in Japan. A case definition for CFS in Japan was adopted in 1991 based on the CDC 1988 criteria, an updated diagnostic guideline is planned.

## Other current terms

### Akureyri Disease

### Iceland disease
This term is used in Iceland.

### Tapanui flu
In New Zealand tho illness can be referred to after the town of Tapanui where the first doctor in the country to investigate the disease, Dr Peter Snow, lived.

# Historical nomenclatures

## Chronic Epstein-Barr virus (CEBV)
Also as Chronic Mononucleosis, the term CEBV was introduced in 1985 by virologists Dr. Stephen Straus and Dr. Jim Jones in the United States. The Epstein-Barr virus, a neurotropic virus that more commonly causes infectious mononucleosis, was thought by Straus and Jones to be the cause of CFS. Subsequent discovery of the closely related human herpesvirus 6 shifted the direction of biomedical studies, although a vastly expanded and substantial body of published research continues to show active viral infection or reinfection of CFS patients by these two viruses. These viruses are also found in healthy controls, lying dormant.

## Yuppie Flu
This was a factually inaccurate term popularized in a November 1990 Newsweek cover story and never official medical terminology. It reflects a stereotypical assumption that CFS mainly affects the affluent ("yuppies"), and implies that it is a form of burnout. CFS, however, affects people of all races, genders, and social standings, and is not a form of flu. The phrase is considered offensive by patients and clinicians.

## Other historical terms

### Atypical poliomyelitis
Name given to describe the 1934 outbreak at the Los Angeles county hospital.

### Royal Free disease
The historically significant outbreak in 1955 at the Royal Free clinic eventually coined the term Myalgic Encephalomyelitis.

### Benign Myalgic Encephalomyelitis
Acheson's term for the 1955 Royal Free Clinic outbreak, it was considered benign in that it was generally nonlethal.  As the potentially devastating nature of the illness became clearer, benign was later dropped from use.

### Epidemic Neuromyasthenia (ENM)

### Epidemic Vasculitis
Also Infectious venulitis (IVN), this term was used to describe an outbreak at the Mercy San Juan Hospital in Sacramento, California by Erich Ryll.

### Raphe Nucleus Encephalopathy