## Basic Introduction

  • Fever is defined as elevation of core body temperature above the normal circadian or daily range (adults 18 - 40yrs: 36.4 - 337.2 deg C; infants 36.50 - 37.4 deg C).
  • Fever can be categorized into Low fever (37.2 -38 deg C), Moderate fever (38.1- 40 deg C) and High fever (>40 deg C).
  • Some authorities define it as a core body (rectal) temperature ≥ 38.0 deg C
  • Sustained fever ≥ 42.2 deg C leads to unconsciousness and permanent brain damage.
  • The body temperature of a normal human being varies during the day by about 0.5 deg C (with lower temperatures in the morning and higher temperatures in the late afternoon and evening). This is known as circadian rhythm.
  • Fever is normally one of the symptoms of a number of diseases.
  • While the course of some diseases that are accompanied by fever will not be changed directly by prompt treatment of fever, the course of other diseases will be positively affected by the treatment. This applies to fever precipitated diseases such as convulsion, delirium, coma, heart failure, heat stroke, and malignant hyperpyrexia.
  • The Fever of Unknown Origin (FUO) or Pyrexia of Unknown Origin (PUO) is a fever that occurs daily for more than 3 weeks and its cause has not been established after a thorough investigation for at least a week.
  • Fever can be described as Remitting, Intermittent, Sustained, Relapsing and Undulant.
  • Remitting fever is where the daily temperatures fluctuate above the normal range by more than 2 deg C.
  • Continuous fever is where the daily temperatures fluctuate above the normal range by more than 1 deg C.
  • Intermittent fever is where the daily temperature drops into the normal range and then rises back above normal.
  • Hectic fever is a form of intermittent fever that is characterized by wide fluctuations of temperatures that cause chills and sweating
  • Sustained fever is where there is persistently raised temperature with little fluctuation.
  • Relapsing fever is where there is alternating feverish and afebrile periods.
  • Undulant fever is where there is a gradual increase in temperature that stays high for a few days then gradually reduces.

## Epidemiology and Statistics

  • 10-20% of FUO will remain unknown even with extensive investigations
  • FUO has a mortality rate of 5-10%
  • About 50% of FUOs are due to viral infections

## Pathology of fever

  • Cytokines, the endogenous pyogenic mediators, stimulate the hypothalamus to produce prostaglandins, which raise the temperature set point.
  • Fever can worsen an existing pulmonary, cardiac or neurologic disease/condition as it increases metabolic rate and the demands on the cardiopulmonary system.
  • It is also a stimulus of febrile seizures, mostly in children

## Causes of acute fever

  • Infections – (the most common cause)

_Bacterial infections

_Viral infections

_Fungal infections (mainly candidiasis)

  • Noninfectious causes such as heatstroke, thyroid storm, Kawasaki disease, vaccination, Acute Rheumatic Fever, thermoregulatory disorders such as seen in diabetes insipidus and anhidrosis, anticholinergics and to a small extent teething in children.
  • Metabolic disorders such as hyperthyroidism
  • Cancers

## Causes of fever of unknown origin (FUO) or chronic fever

  • TB especially miliary TB (the most common cause of FUO in Kenya)
  • Malaria (especially non - falciparum)
  • Infections by atypical microorganisms such as aspergillus and Q-fever
  • Brucellosis
  • Salmonellosis
  • Osteomyelitis
  • Infective endocarditis
  • Viral infections such as HIV and HBV
  • Cancers (not always)
  • Immunogenic diseases such as rheumatic fever and SLE
  • Liver cirrhosis
  • Drug fever
  • Habitual hyperthermia
  • Cyclic neutropenia
  • TNF receptor–associated periodic syndrome
  • Factitious pyrexia
  • Fever (of known origin)
  • Fever of unknown origin (FUO)

## Fever of known origin

  • Tests to confirm diagnosis e.g. BS for malaria

## Fever of unknown origin (FUO)

  • Repeated clinical evaluation
  • Complete blood count
  • Urinalysis
  • Blood culture & sensitivity
  • Urea & electrolyte
  • LFTs
  • Chest X-Ray
  • ESR
  • CRP
  • Diagnostic laparoscopy
  • Tests directed towards suspected diseases such as Rheumatoid factor (Rh Factor), barium studies of GIT, ECG and liver biopsy, among others
  • Not applicable
  • Prevention of underlying cause if it can be established.

a. Beresford RW, Gosbell IB; Pyrexia of unknown origin: causes, investigation and management. Intern Med J. 2016 Sep; 46(9):1011-6.

b. Consolini, D and Alfred, I.; Fever in Infants and Children. Merck Manual, 2016

c. Kenyan Ministry of Health. Clinical guidelines for management and referral of common conditions at levels 4-6. Hospitals. 2009; 3:259-261.http://apps.who.int/medicinedocs/documents/s21000en/s21000en.pdf

d. Ministry of Health, Kenya. Kenya Essential Medicine List (2016). http://publications.universalhealth2030.org/uploads/KEML-2016Final-1.pdf

  • Management of underlying diseases/condition
  • Antipyretics such as paracetamol and acetylsalicylic acid (oral or parenteral) and ibuprofen among others.
  • For the children, immerse in water at 20-25 deg C or tepid sponging, remove excessive clothing, avoid movement and fanning
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