Sentence:  Endymion and the Secretary, after sitting on a pier-end watching some barges, . . . were stricken with the very crisis of <WSD>spring fever</WSD> and lassitude. They considered the possibility of hiring one of the soldiers' two-tiered beds for the afternoon. 
Meaning of the word marked with <WSD> tags:  A feeling of laziness or listlessness associated with the arrival of the warm, comfortable weather of the spring season.