Both, actually! I had experienced two or three flu-like illnesses in the spring before I first experienced crushing fatigue. A few months after those illnesses I slowly realized that I wasn't feeling quite right, and by the end of the summer I was barely functioning. However, after a little over a year of CFS symptoms I gradually recovered. But then after a year of being mostly well, I woke up one morning feeling terribly fatigued, and that's how I've been ever since.