Fever: blessing or curse? A unifying hypothesis.

Considerable data indicate that fever and its mediators have the capacity both to potentiate and to inhibit resistance to infection. It is difficult to reconcile these apparently contradictory observations if they are viewed solely from the standpoint of the individual. However, when viewed from the perspective of the species, both fever's salutary effects on mild to moderately severe infections and its pernicious influence on fulminating infections become teleologically plausible. If one accepts preservation of the species, rather than survival of the individual, as the essence of evolution, fever and its mediators might have evolved as mechanisms both for accelerating recovery of individuals from localized or mild to moderately severe systemic infections in the interest of continued propagation of the species and for hastening the elimination of fulminantly infected individuals who pose a threat of epidemic disease to the species.