What are the common symptoms of fever?

Common Symptoms of High Temperature (Fever)

Fever typically presents with a constellation of constitutional and respiratory symptoms, most commonly including fever itself, headache, muscle aches (myalgia), malaise, fatigue, chills or shivering, and often respiratory symptoms like cough, sore throat, and nasal congestion. 1, 2

Core Symptoms in Adults

The hallmark presentation involves:

• Fever - typically high-spiking, often reaching 39-40°C (102-104°F) 3

• Constitutional symptoms:

  • Headache
  • Diffuse muscle aches and pains (myalgia)
  • Malaise and general weakness
  • Fatigue 4
  • Chills, rigors, or shivering 2

• Respiratory manifestations:

  • Nonproductive cough
  • Sore throat
  • Nasal congestion and rhinitis 1

• Other common symptoms:

  • Increased sweating 4
  • Loss of appetite 4
  • Warmth sensation 4
  • Irritability and restlessness 4

Symptoms in Children

Children often present differently than adults, with additional symptoms that are age-specific 2:

• In infants and young children:

  • High fever that may mimic bacterial sepsis 1, 2
  • Febrile seizures (up to 20% of hospitalized children with influenza) 5, 2
  • Otitis media (ear infections) - occurs in approximately 25% of children under 5 years 5
  • Nausea and vomiting 1, 2
  • Irritability or extreme fussiness
  • Lethargy or listlessness 6

• Neurological symptoms in children:

  • Febrile convulsions (more common with influenza than other causes) 5
  • Altered behavior or personality changes 6
  • Confusion in older children 5

Associated Behavioral Changes

Beyond physical symptoms, fever triggers a spectrum of behavioral changes collectively termed "sickness behavior" 7:

• Social withdrawal
• Loss of interest in usual activities
• Sleep disturbances
• Cognitive dysfunction
• Increased breathing rate 4
• Anxiety or palpitations 4

Critical Pitfalls to Recognize

Not all infected patients are febrile - some may be hypothermic or have normal temperatures, particularly 8:

• Elderly patients
• Immunocompromised individuals
• Patients taking antipyretics or anti-inflammatory drugs
• Those with chronic conditions (heart failure, liver disease, renal failure)

In these populations, look for alternative signs of infection even without fever:

• Unexplained hypotension
• Tachycardia
• Tachypnea
• Confusion
• Lactic acidosis
• Leukocytosis or leukopenia 8

Symptom Severity Correlation

Higher temperatures correlate with more associated symptoms 4. The intensity and number of accompanying symptoms can help predict fever severity, though this relationship varies by individual and underlying cause.

Temperature Measurement Considerations

Fever is generally defined as:

• Core temperature ≥38.0°C (100.4°F) 8, 9
• Or ≥38.3°C (101.0°F) as a single measurement 8, 10

Rectal temperatures typically read a few tenths of a degree higher than oral measurements 8. Normal body temperature (37.0°C/98.6°F) varies by 0.5-1.0°C throughout the day due to circadian rhythm 8.