Fever is a common symptom characterized by an elevated body temperature above the normal range. It is typically a sign that the body is fighting an infection or responding to an inflammatory process.

Definition

Fever is generally defined as an increase in body temperature above the normal daily variation. The threshold for fever can vary slightly depending on the method of measurement, but it is typically considered to be an oral temperature above 38°C or 100.4°F.

Etiology

Infectious Causes

Infections are the most common cause of fever and can be categorized as:

• Viral infections: Such as influenza, common cold, or COVID-19
• Bacterial infections: Including pneumonia, urinary tract infections, or sepsis
• Parasitic infections: Like malaria or toxoplasmosis
• Fungal infections: Such as histoplasmosis or candidiasis

Non-Infectious Causes

• Autoimmune disorders: Lupus, rheumatoid arthritis, or inflammatory bowel disease
• Malignancies: Various types of cancer, particularly lymphomas and leukemias
• Medications: Drug-induced fever from antibiotics, anticonvulsants, or other medications
• Hormonal disorders: Thyroid storm or pheochromocytoma
• Blood disorders: Sickle cell crisis or thrombosis
• Neurological conditions: Brain injury, stroke, or status epilepticus

Clinical Presentation

Fever is often accompanied by other symptoms, which may include:

• Chills and shivering
• Sweating
• Fatigue and weakness
• Headache
• Muscle aches
• Loss of appetite
• Dehydration

The pattern and duration of fever can provide clues about the underlying cause.

Diagnostic Approach

History Taking

• Onset and duration of fever
• Associated symptoms
• Recent travel history
• Medication use
• Exposure to infectious agents

Physical Examination

• Vital signs, including temperature measurement
• Systemic examination to identify potential sources of infection or inflammation
• Skin examination for rashes or other abnormalities
• Neurological assessment

Laboratory Tests

• Complete blood count
• C-reactive protein and erythrocyte sedimentation rate
• Blood cultures
• Urinalysis and urine culture
• Liver function tests
• Specific tests based on clinical suspicion (e.g., malaria smear, viral PCR)

Imaging Studies

• Chest X-ray for suspected pneumonia
• Abdominal ultrasound or CT scan for intra-abdominal sources of infection
• Other imaging as indicated by clinical presentation

Additional Investigations

• Lumbar puncture if meningitis is suspected
• Biopsy of lymph nodes or other tissues if malignancy is a concern
• Autoimmune markers for suspected rheumatological disorders

Management

The approach to managing fever depends on the underlying cause:

• Treating the primary infection or condition
• Antipyretic medications for symptomatic relief
• Ensuring adequate hydration
• Monitoring for complications

It’s important to note that fever itself is often a beneficial response of the body and doesn’t always require treatment unless it’s causing significant discomfort or is dangerously high.