Chronic fatigue syndrome (CFS) is an illness characterized by prolonged, debilitating fatigue and multiple nonspecific symptoms such as headaches, recurrent sore throats, muscle and joint pains, memory and concentration difficulties. Profound fatigue, the hallmark of the disorder, can come on suddenly or gradually and persists or recurs throughout the period of illness. Unlike the short-term disability of say, the flu, CFS symptoms linger for at least six months and often for years. The cause of CFS remains unknown.

The typical patient seeking medical care for CFS is a Caucasian woman in her mid-20s to late 40s. However, anyone at any age — male or female — can develop chronic fatigue syndrome, though cases reported in children under 12 are rare.

Prevalance of Chronic Fatigue Syndrome
The U.S. Centers for Disease Control and Prevention (CDC) conducted a study from 1989 to 1993 to estimate the prevalence of chronic fatigue syndrome; they estimated that four to 8.7 of every 100,000 adults living in the U.S. suffered from chronic fatigue syndrome. However, more recent studies indicate that these projections are underestimated. The prevalence of chronic fatigue syndrome is difficult to measure because the illness can be difficult to diagnose, but in general, it is estimated that perhaps as many as half a million persons in the U.S. have a CFS-like condition, according to the CDC.

Chronic fatigue syndrome does not appear to be a new illness, although it has only recently been assigned the name CFS. Relatively small outbreaks of similar disorders have been described in medical literature since the 1930s. Furthermore, case reports of comparable illnesses date back several centuries.

Interest in what now is called CFS was renewed in the mid-1980s after several studies found slightly higher levels of antibody to Epstein-Barr virus (EBV) in patients with CFS-like symptoms than in healthy individuals. Most of these patients had experienced an episode of infectious mononucleosis (sometimes called mono or the "kissing disease") a few years before they began to experience the chronic, debilitating symptoms of chronic fatigue syndrome. As a result, for a time the CFS-like illness became popularly termed "chronic EBV".

Further investigation revealed that elevated EBV antibodies were not indicators of chronic fatigue syndrome. Some healthy people have high EBV antibodies and some people with CFS do not. Currently, it is not considered useful to test for antibodies to EBV in a patient with symptoms suggestive of chronic fatigue syndrome.

Chronic Fatigue Syndrome Defined
The illness was named chronic fatigue syndrome because it reflects the most common symptom — long-term, persistent fatigue. When the International CFS Study Group updated the definition of chronic fatigue syndrome in 1994, it decided to keep this name until a specific cause for the illness is discovered. (Today, chronic fatigue syndrome also is known as myalgic encephalomyelitis, postviral fatigue syndrome, and chronic fatigue and immune dysfunction syndrome.)

There are no published data to indicate that CFS is contagious, that it can be transmitted through intimate or casual contact or by blood transfusion, or that people with chronic fatigue syndrome need to be isolated in any way.

Copyright 2003 National Women's Health Resource Center Inc. (NWHRC)