Approach to fever

After studying this note, you will be able to systematically approach a patient with fever in the Kenyan clinical setting. Always check specific drug doses and local protocols against the Kenya MoH guideline and the hospital formulary.

Definition

Fever, also known as pyrexia, is an elevation of body temperature above the normal range. In clinical practice, a temperature of 38°C (100.4°F) or higher, measured orally or rectally, is generally considered a fever. Axillary temperatures may require a slightly higher threshold (e.g., 37.2°C or 37.5°C) to be considered feverish due to less accurate measurement.

Anatomy and physiology you need

The hypothalamus acts as the body's thermostat. It receives temperature information from thermoreceptors in the skin, spinal cord, and core body. During infection or inflammation, pyrogens (substances that induce fever) are released. These can be exogenous (e.g., bacterial endotoxins) or endogenous (e.g., cytokines like IL-1, IL-6, TNF-α). Pyrogens act on the hypothalamus, increasing the production of prostaglandin E2 (PGE2). PGE2 then resets the hypothalamic set-point to a higher temperature, leading to the physiological mechanisms that generate heat and reduce heat loss, resulting in fever.

Causes and risk factors

In Kenya, fever is a common presenting symptom with a broad differential diagnosis. Key causes and risk factors include:

• Infectious Causes:
  • Malaria: Endemic in many parts of Kenya. Risk factors include living in or travelling to endemic areas, lack of prompt diagnosis and treatment, and insecticide-treated net (ITN) use.
  • Tuberculosis (TB): High prevalence. Risk factors include close contact with an infectious case, HIV co-infection, malnutrition, overcrowding, and delayed diagnosis.
  • HIV/AIDS: Increased susceptibility to opportunistic infections that cause fever. Risk factors include unprotected sexual contact, intravenous drug use, and mother-to-child transmission.
  • Typhoid Fever: Common in areas with poor sanitation and contaminated water. Risk factors include consumption of contaminated food or water.
  • Pneumonia: Bacterial or viral. Risk factors include young age, old age, smoking, underlying lung disease, and immunocompromise.
  • Urinary Tract Infections (UTIs): More common in women. Risk factors include sexual activity, urinary catheterization, and anatomical abnormalities.
  • Meningitis: Bacterial or viral. Risk factors include close contact, overcrowding, and immunocompromise.
  • Viral Exanthems: Measles, rubella, chickenpox (less common with vaccination).
  • Other Tropical Infections: Dengue fever, Chikungunya, Rickettsial infections.

• Non-Infectious Causes:
  • Rheumatic Fever: A post-streptococcal inflammatory condition. Risk factors include untreated streptococcal pharyngitis, genetic predisposition, and crowded living conditions.
  • Sickle Cell Disease: Vaso-occlusive crises can be accompanied by fever, and increased susceptibility to infections. Risk factors include genetic inheritance.
  • Autoimmune Diseases: Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis.
  • Malignancy: Lymphoma, leukaemia.
  • Drug Fever: Reaction to medications.

Pathophysiology

Pyrogen Release ↓ Stimulation of Hypothalamus ↓ Increased PGE2 Synthesis ↓ Resetting of Thermoregulatory Set-Point ↓ Physiological Responses:

• Shivering (Heat Production)
• Vasoconstriction of Skin Blood Vessels (Reduced Heat Loss)
• Behavioral Changes (e.g., seeking warmth)

↓ Elevated Body Temperature (Fever)

Clinical features

History to elicit

• Fever pattern and onset: Ask about duration, continuous versus intermittent spikes, night sweats, and rigors. Rigors indicate bacteremia or malaria; profound night sweats point toward tuberculosis (TB), lymphoma, or brucellosis.
• Localization symptoms: Cough, hemoptysis, dyspnea (respiratory); dysuria, flank pain (urinary); photophobia, neck stiffness, confusion (central nervous system); abdominal pain, diarrhea (gastrointestinal); joint pains or rashes (rheumatologic/arboviral).
• Exposure and geography: Travel to endemic malaria zones, freshwater contact (schistosomiasis), unpasteurized milk or animal contact (brucellosis, anthrax), tick exposure, or cave visits.
• Host vulnerability: Known HIV status (or last test date), antiretroviral therapy (ART) adherence, sickle cell disease, immunosuppressive therapy, diabetes mellitus, or prior TB treatment.
• Medication history: Over-the-counter antimicrobials or antipyretics (masks fever patterns and culture yields), herbal remedies, or recent drug initiations (drug-induced fever).

Physical examination findings and pathophysiology

• Temperature and hemodynamics: Tachycardia disproportionate to temperature (relative tachycardia) suggests severe sepsis, myocardial involvement, or hypovolemia. Relative bradycardia (Faget's sign) occurs in typhoid fever, yellow fever, and intracellular infections. Hypotension signifies septic shock driven by cytokine-mediated vasodilation.
• Pallor and jaundice: Scleral icterus with pallor indicates brisk intravascular or extravascular hemolysis (severe falciparum malaria, sickle cell hyperhemolytic or aplastic crisis, sepsis-induced DIC, or leptospirosis).
• Lymphadenopathy: Generalized, rubbery, matted nodes indicate TB, HIV seroconversion, or lymphoma. Localized, tender lymphadenitis suggests regional bacterial infection or plague.
• Chest signs: Dullness to percussion, bronchial breathing, and crackles reflect alveolar consolidation (pneumonia). Decreased breath sounds at the lung bases with stony dullness point to pleural effusion (TB, parapneumonic).
• Abdominal examination:
  • Splenomegaly: Reticuloendothelial hyperplasia responding to cleared red cells or intracellular pathogens (malaria, visceral leishmaniasis/kala-azar, brucellosis, schistosomiasis, typhoid).
  • Hepatomegaly or right upper quadrant tenderness: Pyogenic or amoebic liver abscess, acute hepatitis, or congestive hepatopathy from sepsis.
  • Rose spots: Transient erythematous macules on the abdomen reflecting bacterial emboli in Salmonella typhi.
• Neurological examination: Meningismus (nuchal rigidity, positive Kernig’s and Brudzinski’s signs) indicates leptomeningeal inflammation. Depressed GCS, focal deficits, or seizures signal cerebral malaria, bacterial meningitis, or intracranial tuberculoma/toxoplasmosis.
• Dermatologic and mucosal signs: Petechiae, purpura, or ecchymoses suggest meningococcemia, severe sepsis with DIC, or viral hemorrhagic fevers. Oral thrush or hairy leukoplakia points to advanced underlying HIV immunosuppression.

Differential diagnosis

Investigations

Diagnosis and severity

Diagnostic synthesis

Diagnosis requires categorizing the fever by duration (acute <7 days, subacute 1–3 weeks, chronic/FUO >3 weeks), anatomical source (respiratory, CNS, urinary, intra-abdominal, skin/soft tissue, bone/joint), and microbial etiology. In endemic and high-burden settings, prioritize ruling out life-threatening and reversible tropical infections (falciparum malaria, acute bacteremia, TB, cryptococcosis, bacterial meningitis) before entertaining non-infectious rheumatologic or neoplastic etiologies.

Severity assessment (Triage and danger signs)

Use bedside physiological criteria (e.g., quick SOFA) to rapidly stratify risk.

Red flags indicating immediate critical care:

• Altered mental status: GCS <15, confusion, lethargy, or acute delirium.
• Hemodynamic collapse: Systolic blood pressure <90 mmHg or mean arterial pressure <65 mmHg unresponsive to initial fluid challenges.
• Respiratory compromise: Respiratory rate ≥22 breaths/min, central cyanosis, or oxygen saturation <90% on room air (signaling ARDS, severe pneumonia, or metabolic acidosis compensation).
• Bleeding diathesis: Spontaneous mucosal bleeding, purpura fulminans, or petechiae (DIC, severe sepsis, or viral hemorrhagic fever).
• Metabolic failure: Anuria/oliguria (<0.5 mL/kg/h), severe hyperlactatemia, profound hypoglycemia, or macroscopic hemoglobinuria ("blackwater fever").

Management

Immediate Stabilisation

• Triage & Airway, Breathing, Circulation (ABC): Secure the airway if the Glasgow Coma Scale (GCS) is reduced. Administer high-flow oxygen to maintain saturations above 94%. Establish wide-bore intravenous access immediately.
• Fluid Resuscitation: Administer balanced crystalloids (e.g., Ringer's lactate or Normal Saline) for hypoperfusion, shock, or severe dehydration. Assess volume status frequently using blood pressure, capillary refill, chest auscultation, and urine output.
• Antipyresis: Use paracetamol for patient comfort, reduction of metabolic demand, and prevention of febrile encephalopathy. Avoid non-steroidal anti-inflammatory drugs (NSAIDs) if dengue, viral haemorrhagic fevers, peptic ulcer disease, or renal impairment are suspected.
• Empirical Antimicrobial Therapy: Draw blood cultures and thick/thin blood smears before drug administration, but do not delay treatment in the unstable patient:
  • Suspected severe malaria: Intravenous artesunate immediately (preferred over quinine due to lower risk of hypoglycaemia and superior parasite clearance).
  • Suspected bacterial sepsis/bacteraemia: Broad-spectrum IV beta-lactams (e.g., ceftriaxone) to cover common Gram-negative and Gram-positive pathogens.
  • Suspected bacterial meningitis: High-dose IV ceftriaxone plus IV dexamethasone (started before or with the first dose of antibiotics). Add ampicillin if Listeria monocytogenes is a consideration (neonates, elderly, immunocompromised).
• Glycaemic and Electrolyte Control: Check point-of-care blood glucose promptly; malaria, sepsis, and hepatic dysfunction frequently induce severe hypoglycaemia. Correct hypokalaemia or hyponatraemia identified on baseline panels.

Definitive Management

• Targeted Therapy: De-escalate or switch antimicrobials once microscopy, GeneXpert, serology, or culture and sensitivity results return.
  • Uncomplicated Malaria: Artemisinin-based combination therapy (ACT, such as artemether-lumefantrine).
  • Tuberculosis: Standard four-drug anti-TB regimen (rifampicin, isoniazid, pyrazinamide, ethambutol).
  • Enteric (Typhoid) Fever: IV or oral ceftriaxone, azithromycin, or ciprofloxacin (guided by local resistance patterns).
• Source Control: Drain abscesses, debride infected tissue, remove infected intravascular lines, and relieve urinary or biliary obstruction.

Monitoring and Follow-Up

• Vital Signs: Continuous or hourly pulse oximetry, automated blood pressure, temperature charting (4-hourly), and GCS monitoring.
• Urine Output: Catheterise unstable patients; maintain urine output above 0.5 mL/kg/h to monitor end-organ perfusion.
• Laboratory Re-evaluation: Daily full blood count, renal function tests, and repeat blood slides for malaria to confirm clearance of parasitaemia.
• Follow-up: Review at 48 to 72 hours for defervescence. If fever persists, search for drug fever, deep-seated abscesses, nosocomial infections, or wrong initial diagnosis.

Contraindications and Safety

• Artesunate vs. Quinine: If using IV quinine, monitor with serial ECGs (risk of QT prolongation/arrhythmias) and blood sugars (induces hyperinsulinaemic hypoglycaemia).
• Fluid Overload: Exercise extreme caution with aggressive fluids in patients with severe malaria (risk of non-cardiogenic pulmonary oedema) and acute renal failure.
• NSAID Avoidance: Absolute contraindication in undifferentiated tropical fevers with thrombocytopenia due to catastrophic bleeding risks.

Complications and Prognosis

• Prognosis: Excellent with early presentation, prompt diagnostic testing, and targeted antimicrobial coverage. Mortality rises steeply with delays in antibiotic administration for sepsis/meningitis, presence of multi-organ failure, underlying advanced HIV disease, or severe baseline immunosuppression.

High-Yield Exam Points

• "Sepsis Mimics": Non-infectious causes of acute high fever include thyroid storm, heat stroke, neuroleptic malignant syndrome, and severe drug reactions (DRESS).
• Malaria Blind Spot: Never assume fever in an HIV-positive patient is purely opportunistic (e.g., TB or cryptococcus); severe falciparum malaria can co-exist and kill within hours.
• Steroids in Meningitis: Examiners will grill you on the timing of IV dexamethasone: it must be given prior to or concurrently with the first dose of antibiotics to mitigate neuroinflammation; it has zero benefit if delayed.
• Antimicrobial Reflex: The most common wrong first step is prescribing broad-spectrum antibiotics before taking blood for cultures and malaria films in a clinically stable patient.
• The "Typhoid Spine" or Relapse: Typhoid can cause relative bradycardia (Faget's sign—dissociation between high temperature and normal pulse rate). Examiners love asking you to interpret temperature charts showing this finding.
• Post-Artesunate Haemolysis: Patients treated with IV artesunate for severe malaria can develop delayed haemolytic anaemia 1 to 3 weeks later; warn and review them.

Clinical Case

A 28-year-old male presents to the casualty department with a 5-day history of high-grade fever, chills, severe headache, and vomiting. On examination, he is lethargic, jaundiced, and febrile at 39.2°C. Blood pressure is 88/54 mmHg, pulse is 118 bpm, and respiratory rate is 26 breaths/min. Abdominal exam reveals mild splenomegaly. Point-of-care capillary glucose is 2.4 mmol/L.

Questions and Model Answers

1. What are the immediate life-saving interventions required for this patient?

• Answer: Secure the airway, administer high-flow oxygen, establish large-bore IV access, correct hypoglycaemia immediately with intravenous concentrated dextrose (e.g., 50% or 10% dextrose), initiate aggressive crystalloid fluid resuscitation for septic shock, and draw blood for thick/thin smears and cultures immediately.

**2. The blood slide confirms heavy Plasmodium falciparum parasitaemia. What is the drug of choice for definitive treatment, and what major clinical advantage does it have over older alternatives?**

• Answer: Intravenous artesunate. It produces significantly faster parasite clearance and lower overall mortality compared to intravenous quinine, and it does not stimulate pancreatic beta-cells to trigger refractory hyperinsulinaemic hypoglycaemia.

3. If the patient’s fever persists after 72 hours despite appropriate anti-malarial therapy, what complications or co-pathologies must you investigate?

• Answer: Concomitant bacterial sepsis (secondary bacteraemia/Gram-negative sepsis is common in severe malaria), hospital-acquired infection (e.g., aspiration pneumonia, catheter-associated urinary tract infection), drug-induced fever, or splenic/organ abscess formation.

Practice Questions

Question 1

A 34-year-old woman with advanced HIV infection presents with a two-week history of remittent fever, significant weight loss, night sweats, and dry cough. Examination reveals cervical lymphadenopathy and hepatosplenomegaly. Chest X-ray reveals a diffuse, bilateral, uniform micronodular pattern throughout both lung fields. What is the most appropriate definitive diagnostic step to perform next?

A. Sputum Gram stain and routine bacterial culture B. Sputum or lymph node GeneXpert MTB/RIF assay C. Serum cryptococcal antigen lateral flow assay D. Empirical trial of high-dose intravenous co-trimoxazole

Answer: B. Sputum or lymph node GeneXpert MTB/RIF assay Explanation: The clinical picture and classical micronodular chest X-ray indicate miliary tuberculosis, which is common in advanced HIV; rapid confirmation of Mycobacterium tuberculosis and rifampicin susceptibility via GeneXpert using sputum or lymph node aspirate is the definitive next step.

Question 2

A 22-year-old male is admitted with fever, worsening headache, neck stiffness, and photophobia. The clinical team decides to perform a lumbar puncture. Which finding on general and neurological examination constitutes an absolute contraindication to an immediate lumbar puncture before obtaining a neuroimaging scan?

A. Presence of petechial rash on the lower extremities B. Temperature of 40.1°C with sinus tachycardia C. Papilloedema on fundoscopy or focal neurological deficits D. Kernig's sign and Brudzinski's sign both positive

Answer: C. Papilloedema on fundoscopy or focal neurological deficits Explanation: Papilloedema, focal neurological signs, new-onset seizures, or severely depressed GCS indicate raised intracranial pressure or an intracranial space-occupying lesion, which places the patient at imminent risk of fatal brain herniation during lumbar puncture.

Question 3

A 45-year-old farmer from an endemic lake region is admitted with severe fever, rigors, dark urine ("blackwater"), and altered sensorium. Thin film confirms severe Plasmodium falciparum malaria. Intravenous artesunate is commenced. Which of the following is the most critical management rule regarding fluid therapy in this patient?

A. Rapidly infuse crystalloids until central venous pressure reaches elevated levels B. Restrict all fluids to prevent cerebral oedema regardless of urine output C. Give balanced crystalloids cautiously, monitoring closely to avoid pulmonary oedema D. Administer low-dose dopamine infusion to preserve renal tubular blood flow

Answer: C. Give balanced crystalloids cautiously, monitoring closely to avoid pulmonary oedema Explanation: Severe malaria increases pulmonary capillary permeability; aggressive over-hydration easily precipitates fatal non-cardiogenic pulmonary oedema (ARDS), requiring careful fluid balance to maintain perfusion without fluid overload.

Question 4

A 19-year-old university student presents with a 9-day history of escalating step-ladder fever, dry cough, constipation followed by watery diarrhoea, and profound malaise. On examination, his temperature is 39.8°C, but his heart rate is 70 beats/min. Abdomen is mildly distended with vague tenderness. Which of the following best explains the cardiovascular examination finding?

A. Myocardial infarction complicating acute systemic infection B. Sphingomyelinase release causing direct AV node suppression C. Relative bradycardia (Faget's sign) classically seen in enteric fever D. High vagal tone associated with underlying severe dehydration

Answer: C. Relative bradycardia (Faget's sign) classically seen in enteric fever Explanation: The presence of an inappropriately low pulse rate in the setting of significant pyrexia is termed relative bradycardia (Faget's sign), which is a classic diagnostic clue for Salmonella enterica serovar Typhi infection, legionellosis, or intracellular pathogens.

Question 5

A 26-year-old patient who is being treated for a severe febrile illness develops diffuse cutaneous purpura, oozing from intravenous puncture sites, and melena. Platelet count is markedly reduced, prothrombin time (PT) is prolonged, activated partial thromboplastin time (aPTT) is prolonged, and plasma fibrinogen is low. What is the underlying pathophysiological mechanism?

A. Selective autoimmune clearance of platelets via IgG antibodies B. Systemic consumptive coagulopathy driven by unregulated thrombin generation C. Vitamin K deficiency secondary to prolonged oral broad-spectrum antibiotic therapy D. Direct endothelial invasion causing primary capillary fragility without clot formation

Answer: B. Systemic consumptive coagulopathy driven by unregulated thrombin generation Explanation: Disseminated Intravascular Coagulation (DIC) in sepsis is driven by widespread tissue factor exposure and systemic cytokine release, causing widespread microvascular thrombosis and consumption of clotting factors and platelets, leading to paradoxical severe haemorrhage.

Drafted with AI assistance from standard references and reviewed for structure. Check details against your lecture notes and the Kenya MoH guideline.