Symptoms of chronic fatigue syndrome (CFS) may occur suddenly after you have a cold, bronchitis, hepatitis, or an intestinal infection. Symptoms may follow a bout of infectious mononucleosis (mono), which is caused by a virus that temporarily saps your energy. CFS can also begin after a period of high stress. Sometimes it develops more gradually, with no clear illness or other event noted as a starting point.

Unlike flu symptoms that usually go away in a few days or weeks, symptoms of CFS persist or recur in cycles for at least six months in 50% of time. CFS symptoms vary from person to person. Since 1994, the guidelines for diagnosing CFS include, in addition to a six-month history of fatigue that is not relieved with bed rest, at least four of the following eight symptoms:

  • Muscle aches
  • Joint pain without swelling or redness
  • Headaches
  • Trouble with short-tern memory or concentration, forgetfulness, or confusion
  • Sore throat
  • Tender lymph nodes
  • Trouble sleeping or not feeling rested after sleep
  • Worsening symptoms 24 hours or more after exercise

In addition to the eight diagnostic symptoms, patients with CFS can also suffer from:

  • Mood swings
  • Depression
  • Anxiety
  • Dizziness
  • Chronic pain
  • Irritable bowel
  • Low blood pressure
  • Hyperventilation
  • Sensitivity to many chemicals