Fever of other or unknown origin

**Definition:** An abnormal elevation of body temperature of unknown origin, often as a result of a pathologic process.

**Long definition:** Fever of unknown origin is defined by the following criteria: 1) temperatures of >38.3°C on several occasions; 2) a duration of fever of >3 weeks; 3) failure to reach a diagnosis despite 1 week of inpatient investigation.

**Exclusions:** - fever of unknown origin in newborn - Malignant hyperthermia due to anaesthesia