Chronic fatigue syndrome (also called CFS) is a disorder without a known cause, although CFS may be related to a previous infection. CFS is a state of chronic fatigue that exists without other explanation for 6 months or more and is accompanied by cognitive difficulties (problems with short-term memory or concentration). You may have CFS if you meet the following criteria:

• If you have severe chronic fatigue for 6 months or longer and all other known conditions that could cause fatigue have been excluded by your health care provider

• If you simultaneously have 4 or more of the following symptoms: significant problems with short-term memory or concentration, sore throat, tender lymph nodes, muscle pain, pain in several joints without swelling or redness, headaches that are different in pattern or severity from previous headaches, feeling tired and unrefreshed even after sleeping, and extreme tiredness lasting more than 24 hours after you exercise or exert yourself

Chronic fatigue syndrome affects tens of thousands of people. It occurs more commonly in females than in males. This condition occurs most commonly in young to middle-aged adults. People with CFS are often unable to perform normally at work and home because of their long-term fatigue and problems with short-term memory. This can lead to depression, but depression is not a cause of CFS.

Researchers have long suspected and searched for a virus as the cause. It is now suspected that chronic fatigue syndrome, like cancer, represents a cluster of clinically distinct diseases whose origins may lie in a combination of factors: one or more viruses, environmental toxins, stress and genetic predisposition.

The CDC(center for disease control) estimates in the early 1990s, based on people receiving medical treatment, projected the number of people with chronic fatigue syndrome to be 10 per 100,000. The 1999 prevalence study, which evaluated a large random sample of people in metropolitan Chicago, reveals rates of 422 people per 100,000. When a whole community was studied, not just people under a doctor's care, the numbers increased significantly. The new numbers reveal 800,000 adults in the United States have chronic fatigue syndrome, twice the number of people with multiple sclerosis. Contrary to the "yuppie flu" myth, the 1999 study showed the illness to be wide- spread in low-income and minority communities, with Latinos and Mexican Americans exhibiting higher rates than Caucasians. Even more shocking, the study revealed that only 10 percent of those with chronic fatigue syndrome had been previously diagnosed. Thus, 90 percent of people with the illness are struggling to maintain normal lives without the benefit of medical diagnosis or treatment. The study reveals a hidden epidemic that hits women disproportionately, devastates lives and costs billions of dollars annually

Other myths new research is debunking:

Myth: People with chronic fatigue syndrome are "merely tired," perhaps from overwork or stress. Fact: People with the illness have a complex, multi-system illness, showing abnormalities in the immune, neurological, endocrine and other systems. The profound exhaustion of a person with chronic fatigue syndrome bears no relation to the fatigue a healthy person feels as the result of a busy life. People severely ill with chronic fatigue syndrome have a functional level that is significantly lower than that of someone with cancer undergoing chemotherapy, someone with heart disease or multiple sclerosis.

Myth: People who claim to have chronic fatigue syndrome are really de- pressed. It's "all in the head." Fact: In the 1999 study, 60 percent of those diagnosed with chronic fatigue syndrome had never experienced a psychiatric illness, such as depression, before the onset of the illness. People with depression generally feel better after exercise; people with chronic fatigue syndrome feel worse after exercise. People with depression typically have enlarged adrenal glands; people with chronic fatigue syndrome often have small, low- functioning adrenals.

New research also reinforces the understanding that the illness can involve significant transient (as opposed to permanent) brain damage. Brain scans have revealed lesions in people with the illness, as well as a decreased blood flow to the cerebrum and midbrain.

People with chronic fatigue syndrome have symptoms similar to a concussion: brain fog, confusion, memory loss and difficulty processing sensory input. A simple trip to the grocery store can be exhausting as the brain struggles to process all the light, noise and movement. In 2002, the U.S. diagnostic code for chronic fatigue syndrome will be moved from "general symptoms-malaise and fatigue" to "other disorders of the brain."

A diagnosis is made when a person meets the Centers for Disease Control definition: clinically evaluated, unexplained, persistent fatigue that is of new onset, is not alleviated by rest, lasts over six months and results in substantial reduction in previous levels of activity. In addition, four or more of the following symptoms must be present for over six months: impaired memory or concentration, sore throat, tender cervical or axial lymph nodes, muscle pain, multi-joint pain, new headaches, unrefreshing sleep and post-exertion malaise lasting more than 24 hours.

Chronic fatigue syndrome disrupts work and family life for hundreds of thousands of people. This has important implications for public health and policy. Our new understandings about the illness should galvanize support from legislators, the research community and the general public for increased research and education about this major public health concern.

History of Chronic Fatigue Syndrome

Chronic Fatigue Syndrome does not appear to be a new illness. Relatively small outbreaks of similar disorders have been described in the medical literature since the 1930s. Furthermore, case reports of comparable illnesses date back several centuries, some possibly linked to bacterial, viral, or protozoal infections such as brucellosis, yellow fever, hepatitis, influenza, and malaria.

Fatigue syndromes also have been long recognized outside the setting of an infectious illness. For example, the clinical descriptions of Chronic Fatigue Syndrome and the rheumatologic disorder fibromyalgia, first described in the l9th century, overlap considerably. Chronic Fatigue Syndrome and depression also share some symptoms.

Interest in what now is called Chronic Fatigue Syndrome was renewed in the mid-1980s after several studies found slightly higher levels of antibody to Epstein-Barr virus (EBV) in patients with Chronic Fatigue Syndrome-like symptoms than in healthy individuals. Most of these patients had experienced an episode of infectious mononucleosis a few years before the onset of their new chronic, debilitating illness. As a result, for a time the Chronic Fatigue Syndrome-like illness became popularly termed "chronic EBV."

In subsequent investigations, it became clear that elevated EBV antibody titers were not diagnostic for Chronic Fatigue Syndrome: Some healthy people have high EBV titers and some people with Chronic Fatigue Syndrome do not. Currently, it is not considered useful to test for antibodies to EBV in a patient with symptoms suggestive of Chronic Fatigue Syndrome. More than 90 percent of adults in developed countries have been exposed to EBV by age 30, and moderately elevated antibody titers have not been associated with any EBV-related disease. Chronic EBV is an inappropriate label for this illness and should be abandoned.

The name "chronic fatigue syndrome," chosen because it reflects the most common symptom, was selected for the illness by a group of experts in 1988. When the International Chronic Fatigue Syndrome Study Group updated the case definition, they decided to retain this name until the discovery of a specific cause of or marker for the illness suggests a more fitting name.

Symptom complexes similar to Chronic Fatigue Syndrome also are known as epidemic neuromyasthenia, myalgic encephalomyelitis, postviral fatigue syndrome, and chronic fatigue and immune dysfunction syndrome in different parts of the world. No immune dysfunction specific to Chronic Fatigue Syndrome has been found, however, and there is no evidence linking encephalomyelitis to the pathology of the illness.