The U.S. Centers for Disease Control and Prevention (CDC) have suggested that CFS may be the end stage of multiple different conditions, rather than one unique condition. In fact, 10 to 12 percent of people with Epstein-Barr virus, Ross River virus, and Coxiella burnetti develop a condition that meets the criteria for a CFS diagnosis.
People with CFS sometimes have weakened immune systems, but doctors don’t know whether this is enough to cause the disease. Additionally, people with CFS sometimes have abnormal hormone levels, but doctors haven’t yet concluded whether this is significant.
The symptoms of CFS vary from person to person and based on the severity of the condition. The most common symptom is fatigue that is severe enough to interfere with your daily activities. For CFS to be diagnosed, fatigue must last for at least six months and must not be curable with bed rest, and you must have at least four other symptoms as well.
You may also experience illness or extreme fatigue after physical or mental activities. This can last for more than 24 hours after the activity.
People are sometimes affected by CFS in cycles, with periods of feeling worse and then better again. Symptoms may sometimes even disappear completely (remission). However, it’s still possible for them to come back again later (relapse). The cycle of remission and relapse can make it difficult to manage your symptoms.