In some cases the symptoms are so severe that the person becomes disabled and unable to work or attend school for a prolonged, indefinite time.
Research is ongoing around the world to determine the cause.
Many people report they become ill after a viral infection. Others became ill after surgery, an accident, exposure to chemicals, childbirth, severe stress, etc. Research is investigating the role of viruses and other predisposing factors such as genetics, toxins, and other immune stressors. There is not diagnostic test. M.E. may be diagnosed if a person's normal activity has been substantially effected, they exhibit the symptoms, and other causes of the symptoms have been investigated.