This alteration is caused by a shift to pathological values of the hypothalamus regulation system, due to the action of endogenous chemical mediators: pyrogenic cytokines. These endogenous pyrogens are released in response to the action of infectious agents and their products (exogenous pyrogens) or to inflammatory and necrotic foci of a non-infectious nature. Fever is, therefore, an acute phase immune response to various causes capable of inducing infection and / or disease and is a common clinical sign of many medical conditions.
The most common example of a pathology characterized by fever is seasonal flu, to which the organism responds with an increase in temperature, such as to neutralize the action of the viruses involved in the infectious disease.