Pyrexia (or fever) is a clinical sign, indicated by an abnormally elevated core body temperature, which is defined by several medical societies as ≥38.3°C (≥101°F). The temperature elevation may be persistent or episodic. If the body temperature is greater than 41.5°C - a rare phenomenon - it is known as hyperpyrexia.

The commonest cause of fever is infection, in one study of hospital inpatients accounting for ~70% cases 1. Other frequent causes are inflammatory disease, malignancies and medication-related fevers. Pyrogenic is the term used for anything that causes pyrexia. When the cause of a fever remains unexplained it is termed a pyrexia of unknown origin (PUO).


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Article information

rID: 67278
Section: Signs
Synonyms or Alternate Spellings:
  • Antipyretics
  • Antipyretic
  • Pyrogenic
  • Fevered
  • Feverish
  • Febrility
  • Febrile
  • Pyrexias
  • Fevers
  • Pyrexial
  • Ague
  • Fever

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