What is Chronic Fatigue Syndrome?

Chronic fatigue syndrome (CFS) is characterized by chronic, debilitating fatigue that lasts at least six months. The fatigue is not relieved by bed rest and is often made worse by physical or mental activity. It is accompanied by symptoms that are severe enough to impair or interfere with daily activities. People who have CFS perform at a significantly lower level compared to their activity prior to the onset of the illness.