Typical fever curves

The height of the fever is not proportionate with the underlying cause.

So high fever alone does not mean a serious illness. The same virus once may cause a very high fever in the same child and in another time none at all. So, low fever may also mean a disease that needs to be taken seriously (such as pyelitis); but a simple toothache can also cause very high fever.

Fever usually takes not one, but a few days with a few short breaks.

However, there are typical febrile episodes that can be associated with certain diseases. Thus, the fever may partially help to identify the cause.

  • a) Febris continua: persistent high fever with daily fluctuations below 1°C. (e.g. may be caused by pneumonia on a large surface, central fever, Far Eastern infections)
  • b) Febris remittens: daily fluctuations higher than 1.5°C, but the temperature does not fall below the normal range. (e.g. may be caused by viruses, bacterial pus, or malaria)
  • c) Febris intermittens: temperature fluctuations are high, and temperatures sometimes return to normal. (e.g. may be caused by sepsis (commonly known as blood poisoning), or abscess)
  • d) Subfebrility: slight elevation in temperature with daily fluctuations below 1.5°C. (e.g. may be caused by reaction to cold/stress, or viruses)
  • e) Febris undulans: fever lasts for days alternating with longer non-febrile periods for more than five days. (e.g. may be caused by rare pathogens)
  • f) “Modified fever” means an affected fever resulting from the pharmacological control of a fever.
  • g) “Persistent and recurrent fever” means persistent fever, fever of unknown origin (FUO), recurrent fever, and periodic fever. For example, “fever of unknown origin”, which refers to fever periods of at least 38.5°C over a period of at least three days lasting longer than three weeks, and yet its cause remains unknown. (Investigating this is a careful specialist task, since about 90% of their origins can be found today. These include PFAPA syndrome (formerly known as Marshall's syndrome), and cyclic neutropenia.)


Refer to the literature by numbers in this document here: References

Version update: 08th March 2020