About Fever (Pyrexia)

What causes Fever

Fever or Pyrexia is defined as an elevation of the body temperature that exceeds the normal daily variation of 36.5°C -37.5 °C or (97.7°F -99.5°F). 98.6° F (37° C) is usually considered a normal body temperature

Types of Fever

Fever is classified based on the duration and height of the temperature

1. Based on Duration of Fever

Classification of fever based on the duration

Acute<7 days› Malaria
› Viral
SubacuteUp to 2 weeksTyphoid fever
Chronic>2 weeksTuberculosis

2. Based on Height of Temperature

Classification of fever based on temperature height

TemperatureFahrenheit (°F)
Mild/low-grade fever100.5–102.2
Moderate grade fever102.2–104.0
High-grade fever104.1–106.0

Causes of Fever

Any substance that induces fever is called a pyrogen.

The disorders that may cause fever are

  • Infectious Diseases (Viral, bacterial, fungal (most common cause))
    • Respiratory tract infections
    • Gastrointestinal infections
    • Urinary tract infections (UTIs)
    • Skin infections
    • Malaria
  • Inflammatory conditions
    • Rheumatoid arthritis
    • Lupus
  • Cancer
  • Physiological stress
  •  Environmental Factor
    • Heatstroke
  • Drugs
    • Cocaine, Amphetamines, etc

What are the symptoms

  • Shivering
  • Lack of appetite and generalized weakness & malaise
  • Sleepiness
  • Headache
  • Inability to concentrate

Warning Signs of Fever

  • Temperature >103oF
  • Shortness of breath
  • Mental clouding
  • Persistent headache
  • Fever does not subside in 48 hrs

Diagnostic Evaluation

dentifying the cause of fever by doing lab tests can help treat the patient better.

  • CBC (complete blood count )
  • Blood cultures/ Widal test
  • Chest x-ray
  • Urinalysis and urine culture

Treatment at Home