Meanings of feverish concentration in English

And the feverish concentration of the piece-work sewers in the window of the loft building.

Lawanne worked upon his book, but by fits and starts, working when he did work with a feverish concentration.

She licked her lips and returned her attention to me with a look of feverish concentration taking over her face.

Cracknell was sat close to the spectators' pavilion, writing with feverish concentration, wringing every last second of light from the fading day.

Her brows were always wrinkled with the feverish concentration of one anxiously doing one thing while anxiously thinking of another thing waiting to be done.