[potiuper]

Hyperthermia differs from fever in that the body's temperature set point remains unchanged. https://en.wikipedia.org/wiki/Hyperthermia

[sandworm101]

Yes but the extra heat in the body causes the same cascade of chemical changes that will eventually kill. Initial treatment is different, to a point. If a fever is too high it will suddenly need the same treatment as hyperthermia: direct cooling.