The only problem with this definition is that it exludes people with gradual onset disease. But what you describe is ME for me. Before I got severely and chronically sick 10 years ago I had PVFS lasting 4-6 months many times. It was always triggered by a serious virus like chicken pox, measles or influenza, never colds. This was not just fluey tiredness but neuroimmune disease with cognitive dysfunction, dysautonomia, neuropathic pain, flu-like malaise, PEM, alcohol intolerance, etc. The reason why I became so ill this time around is because the triggering influenza infection was REALLY severe. But the present illness is the same one I've been getting on and off for years.
What you are describing sounds like the typical flare ups of ME as described by Ramsay. I think the cause of much of the confusion is thinking of ME in the same way as CFS. With CFS requiring long term fatigue or problems functioning for six months it doesn't allow for the periods of normal/almost normal health that ME often has. Remember ME was described from epidemics so they knew their patients had it right from the start and were able to follow them. Many seemed normal much of the time.
It is like MS. With the use of MRIs MS is being diagnosed much sooner than it used to be. People have episodes then are well and it can be years later that they develop what used to be recognized as MS. But they have had MS from the outset.
In many people with ME the ONSET is sudden, but the disease progression is GRADUAL with each infection or period of overactivity leading to more severe disease.
The CFS definitions are more likely to pick up EBV type infections where the initiating infection never seems to lift but that is not typical in ME. The initial illness can be trivial, the initial ill health minimal but the damage is done and you have the disease eating away at you causing damage that is not readily apparent.
Mithriel