CFS may develop after what seems to be a typical viral illness. Often, people say that their illnesses started during a period of high stress. In others, CFS develops more gradually, with no clear illness or other event starting it.

People with CFS say the extreme exhaustion is similar to that felt with mononucleosis, the flu, a lingering hangover, or untreated sleep apnea. The extreme weakness of chronic fatigue does not go away. It continues to drain the person for months and years.

Typical symptoms include muscle and joint aches, fatigue, and weakness. Other possible symptoms include abdominal pain, bloating, chest pain, dizziness, dry eyes or mouth, jaw pain, morning stiffness, night sweats, short-term memory loss, mental problems such as panic attacks, shortness of breath, skin sensations, tingling sensations, and weight loss. CFS symptoms either hang on or often come and go for more than 6 months. For most people, CFS symptoms reach a plateau early in the course of illness. After that, they wax and wane, and may go away gradually over time.

Anyone can have CFS. Women are about 2 times more likely to develop CFS than men, but researchers aren't sure why this is so. CFS is more common in whites than in other races and ethnicities. CFS also is known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

No test has been shown to be able to diagnose CFS. In part, this is because doctors don't know what causes it. And because the symptoms are vague or are similar to other diseases, CFS can be difficult to diagnose even based on symptoms. A complete history and physical exam are needed to rule out conditions that mimic CFS. In certain cases, blood tests may be ordered to rule out diseases like multiple sclerosis and lupus (systemic lupus erythematosus) that take years to show symptoms. Even after a tentative diagnosis of CFS, new symptoms might show that the problem is something other than CFS.

Scientists are not sure what causes CFS, although many theories have been put forth. It's clear that CFS is not caused by anemia, hypoglycemia, allergies, yeast infections, or the Epstein-Barr virus. At this time, no one knows the cause, although CFS seems to involve interactions between the immune and central nervous systems. It does not appear to be an infectious disease, passed from one person to another.

No specific treatment is available for CFS. But cognitive behavioral therapy and graded exercises may help. CBT involves talking about the condition a qualified counselor. Graded exercise is exercise therapy that starts slowly and gradually adds more activity over time. Certain medicines can ease some of the symptoms. Nonsteroidal anti-inflammatory medicines (NSAIDs) can ease body aches and fever. Antihistamines can alleviate a runny nose and other allergy-like symptoms. Low doses of antidepressants may help with sleep problems and depression from the illness. A rehab specialist can help plan activities for the times when a person with CFS has the energy to do them.

These statements are all rumors that have circulated about CFS, but none has been proved.