Fever: Classification

It is well known that in an acute febrile reaction, human body temperature (especially in children) rises rapidly to values between 40 to 41°C, but almost never reaches values above about 41°C. This is independent of the cause of the fever or the location of the temperature measurement.

The following is an illustration of the most relevant types of fever:

Fever type	Description	Typical diseases
Febris continua (continuous fever)	The fever is circa 39 °C and diurnal fluctuations < 1 °C. It lasts for several days	Spotted fever, lobar pneumonia, rickettsioses, typhoid fever, paratyphoid fever, scarlet fever, tularemia.
Febris remittens (remittent fever).	The fever with daily fluctuations around 1-2 °C, but also permanently exceeds the normal temperature.	Tuberculosis
Febris intermittens (intermittent fever)	Fever spikes with chills alternate with normal and also hypothermia; diurnal fluctuations >2 °C with chills and/or circulatory regulation	Acute brucellosis, endocarditis, malaria, miliary tuberculosis, osteomyelitis, salmonellosis, sepsis.
Relapsing fever (recurrent fever, recurrent fever).	Short periods of fever are interrupted by fever-free days	Malaria (marsh fever, alternating fever), relapsing fever,
Febris undulans (undulant fever; undulating fever; also called Pel-Ebstein fever).	The fever progresses in waves with fever peaks up to 40 °C Febrile phases of 3-10 days with fever-free intervals of comparable length	Brucellosis, Hodgkin’s lymphoma (synonyms: Hodgkin’s disease, lymphogranulomatosis).
Double peak fever	After a few fever-free days, a second febrile phase occurs after an initial fever peak	Dengue fever, yellow fever, influenza (including pandemic/avian influenza or “new flu“/” swine flu“), measles.