Chronic fatigue syndrome beginning suddenly occurs seasonally over the year

The fact that many patients with chronic fatigue syndrome (CFS) have an inf ectiouslike sudden onset to their illness has led to the hypothesis that CF S is a medical illness. If CFS were, on the other hand, a psychiatric disor der related to symptom amplification, one would expect illness onset to occ ur randomly over the calendar year. This study tested that hypothesis with 69 CFS patients whose illness was on the more severe side of the illness sp ectrum; all patients reported sudden illness onset with the full syndrome o f sore throat, fatigue/malaise, and diffuse achiness developing over no lon ger than a 2-day period. Date of illness onset was distinctly nonrandom. It peaked from November through January and was at its lowest from April thro ugh May. These data support the hypothesis that an infectious illness can t rigger the onset of CFS.