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Infectious Diseases

Yellow Fever

An acute viral haemorrhagic fever caused by the yellow fever virus (a Flavivirus), transmitted by infected mosquitoes (primarily Aedes species in urban cycles, Haemagogus/Sabethes in jungle cycles). A notifiable disease.

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Referral and warning signs

When to refer

Refer ALL suspected cases to Hospital (RR) for diagnosis confirmation, supportive management, and monitoring for complications, especially if jaundice or bleeding develops. Immediate NOTIFICATION to public health authorities.

Red flags

  • Jaundice.
  • Any signs of bleeding (epistaxis, haematemesis, melena, petechiae).
  • Oliguria / Anuria.
  • Signs of shock.
  • Altered mental status.
  • Persistent vomiting.

Signs and symptoms

  • Incubation period: 3-6 days.
  • Phase 1 (Acute Phase):
  • - Sudden onset of fever, chills, severe headache.
  • - Back pain, generalized myalgia.
  • - Nausea, vomiting.
  • - Fatigue, prostration.
  • - Facial flushing, conjunctival injection.
  • - Relative bradycardia (Faget's sign: high fever with slow pulse) may occur.
  • - Most patients improve and recover after this phase (3-4 days).
  • Phase 2 (Toxic Phase - occurs in ~15% of cases, 1-2 days after initial remission):
  • - Recurrence of high fever.
  • - Jaundice (liver damage) - hence the name 'yellow fever'.
  • - Haemorrhagic manifestations: Epistaxis, gum bleeding, haematemesis ('black vomit'), melena, petechiae, ecchymoses, bleeding from injection sites.
  • - Renal failure: Oliguria/anuria, proteinuria.
  • - Abdominal pain (epigastric).
  • - Deterioration of clinical status, delirium, shock, multi-organ failure.
  • - High mortality (~20-50%) in patients entering toxic phase.

Risk factors

  • Lack of vaccination.
  • Living in or travelling to endemic areas (tropical South America, sub-Saharan Africa).
  • Exposure to infected mosquitoes (Aedes aegypti in urban areas, forest mosquitoes in jungle cycle).
  • Activities in forested areas (hunters, loggers).

Diagnosis

Clinical assessment

Suspicion based on acute febrile illness with jaundice and/or haemorrhagic signs in a person living in or recently returned from an endemic area, especially if unvaccinated.

Differential diagnosis

  • Severe Malaria.
  • Other Viral Haemorrhagic Fevers (Ebola, Marburg, Lassa, Dengue).
  • Leptospirosis.
  • Viral Hepatitis (acute A, B, E).
  • Rickettsial infections.
  • Meningococcaemia.
  • Toxic shock syndrome.

Investigations

  • Laboratory Testing (Requires specialized lab):
  • - RT-PCR: Detects viral RNA in blood during early phase (first ~5 days of illness).
  • - Serology: Detection of Yellow Fever-specific IgM antibodies (appears ~5 days after onset) or IgG (later/convalescent). ELISA common.
  • Other Tests (support diagnosis, assess severity):
  • - LFTs: Markedly elevated AST and ALT (often AST>ALT initially), elevated Bilirubin.
  • - Renal function tests: Elevated Urea/Creatinine.
  • - FBC: Leukopenia, Thrombocytopenia.
  • - Coagulation studies: Prolonged PT/INR, aPTT.
  • - Urinalysis: Proteinuria.

Diagnostic criteria

Clinical suspicion + Epidemiological link + Laboratory confirmation (PCR or IgM serology).

Management

Non-pharmacological management

  • Hospital Admission (especially if toxic phase develops).
  • Supportive Care: (Mainstay of treatment)
  • - Bed rest.
  • - Fluid management (maintain hydration, oral or IV, monitor carefully).
  • - Nutritional support.
  • - Protect patient from further mosquito bites (bed net) during first 5 days of illness to prevent transmission.
  • Management of Complications:
  • - Treat shock (fluids, vasopressors if needed).
  • - Manage bleeding (blood products if available/indicated).
  • - Treat renal failure (dialysis if available/indicated).
  • - Treat secondary bacterial infections.
  • - Intensive care support may be needed.

Pharmacological treatment

  • No specific antiviral drug treatment.
  • Symptomatic Treatment:
  • - Antipyretics: Paracetamol preferred for fever/pain.
  • - Avoid Aspirin and NSAIDs due to increased bleeding risk.
  • - Antiemetics for nausea/vomiting.

Monitoring

Monitor vital signs, hydration status, urine output, signs of bleeding, jaundice, renal/hepatic function.

Complications

  • Hepatic failure.
  • Renal failure.
  • Haemorrhage / DIC.
  • Shock.
  • Myocarditis.
  • Encephalopathy.
  • Secondary bacterial infections.
  • Death.

Prevention

  • Vaccination: Highly effective live-attenuated Yellow Fever vaccine (17D strain) provides long-lasting (likely lifelong) immunity. Recommended for residents of and travellers to endemic areas. Required for entry into many countries (International Health Regulations).
  • Mosquito Control:
  • - Eliminate Aedes breeding sites (stagnant water containers around homes).
  • - Use of insecticides (larvicides, adulticides).
  • - Personal protection measures: Use insect repellent (DEET), wear long sleeves/trousers, use bed nets, screen houses.
  • Surveillance and outbreak response.

Patient education

  • Explanation of the illness and mosquito transmission.
  • Need for hospitalization if severe.
  • Importance of supportive care (fluids, rest).
  • Avoidance of aspirin/NSAIDs.
  • Mosquito protection measures for patient (prevent spread) and community.
  • Importance of vaccination for prevention.

Uganda-specific notes

Yellow Fever is endemic in parts of Uganda, with periodic outbreaks. Vaccination is the cornerstone of prevention and required for international travel from/to Uganda. Diagnosis requires specialized testing (UVRI). Management is supportive.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 2, Section 2.3.6.2

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 18 (Immunization - Yellow Fever Vaccine)

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