Strong's:πυρέσσω to be on fire, i.e. (specially), to have a feverDerivation: from G4443;KJV Usage: be sick of a fever. G4443
πυρέσσω puressō poo-res'-so From G4443; to be on fire, that is, (specifically) to have a feverKJV Usage: be sick of a fever.
πυρετός puretos poo-ret-os' From G4445; inflamed, that is, (by implication) feverish (as noun, fever)KJV Usage: fever.