What is chronic fatigue syndrome (CFS)?
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, chronic fatigue syndrome symptoms linger for at least six months and often for years. The cause of chronic fatigue syndrome remains unknown.
Chronic fatigue syndrome is a debilitating and complex disorder characterized by profound fatigue of six months or longer duration that is not improved by bed rest and that may be worsened by physical or mental activity. Persons with chronic fatigue syndrome (CFS) most often function at a substantially lower level of activity than they were capable of before the onset of illness. In addition to these key defining characteristics, patients report various nonspecific symptoms, including weakness, muscle pain, impaired memory and/or mental concentration, insomnia and post-exertional fatigue lasting more than 24 hours. In some cases, chronic fatigue syndrome can persist for years.
Chronic fatigue syndrome may occur after an infection such as a cold, bronchitis, mononucleosis, hepatitis or intestinal illness. It can start during or shortly after a period of high stress or come on gradually without any clear starting point and any obvious cause. Chronic fatigue syndrome is a flu-like condition that can drain your energy and sometimes last for years. People previously healthy and full of energy may experience extreme fatigue, weakness and headaches as well as painful joints, muscles and lymph nodes.
Chronic fatigue syndrome is the most common name for this disorder, but it also has been called chronic fatigue and immune disorder (CFIDS), myalgic encephalomyelitis, low natural killer cell disease, post-viral syndrome, Epstein-Barr disease, and Yuppie flu. Chronic fatigue syndrome has so many names because researchers have been unable to find out exactly what causes it and because there are many similar, overlapping conditions. Reports of a CFS-like syndrome called neurasthenia date back to 1869. Later, people with similar symptoms were said to have fibromyalgia because one of the main symptoms is myalgia, or muscle pain. Because of the similarity of symptoms, fibromyalgia and chronic fatigue syndrome are considered to be overlapping syndromes.
In the early to mid-1980s, there were outbreaks of chronic fatigue syndrome in some areas of the United States. Doctors found that many people with chronic fatigue syndrome had high levels of antibodies to the Epstein-Barr virus (EBV), which causes mononucleosis, in their blood. For a while they thought they had found the culprit, but it turned out that many healthy people also had high EBV antibodies. Scientists have also found high levels of other viral antibodies in the blood of people with chronic fatigue syndrome. These findings have led many scientists to believe that a virus or combination of viruses may trigger chronic fatigue syndrome.
Chronic fatigue syndrome was sometimes referred to as Yuppie flu because it seemed to often affect young, middle-class professionals. In fact, chronic fatigue syndrome can affect people of any gender, age, race, or socioeconomic group. Although anyone can get chronic fatigue syndrome, most patients diagnosed with chronic fatigue syndrome are 25-45 years old, and about 80% of cases are in women. Estimates of how many people are afflicted with chronic fatigue syndrome vary due to the similarity of chronic fatigue syndrome symptoms to other diseases and the difficulty in identifying it. The Centers for Disease Control and Prevention (CDC) has estimated that 4-10 people per 100,000 in the United States have chronic fatigue syndrome. According to the CFIDS Foundation, about 500,000 adults in the United States (0.3% of the population) have chronic fatigue syndrome. This probably is a low estimate since these figures do not include children and are based on the CDC definition of chronic fatigue syndrome, which is very strict for research purposes.