Interfers- activity. Chronic fatigue syndrome or cfs is essentially is too much fatigue to function in your daily life. The fatigue interfers with your activities and stops you from doing them. It is defined as a "debilitating and complex disorder characterized by profound fatigue that is not improved by bed rest and that may be worsened by physical or mental activity." - reference cdc website cdc/gov/cfs.
Not easy. This condition, perhaps as a sequel to a viral illness, causes tiredness, muscle aching, joint pain and mental fatigue. More common in women, it can affect all age groups, responds poorly to medication, and in extreme cases leaves the patient mostly bedridden. There is no laboratory testing that makes the diagnosis. There are strong psychological underpinnings.