Lassa Fever

Aka: Lassa Fever

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II. Pathophysiology

  1. Lassa virus is an arenavirus that is classified as a hemorrhagic fever
  2. First recognized Outbreak: Lassa, Nigeria (1969)
  3. Endemic to West Africa
    1. Nigeria
    2. Liberia
    3. Sierra Leone
    4. Senegal
    5. Gambia
    6. Guinea
    7. Ghana
    8. Burkina Faso (Upper Volta)
    9. Mali
    10. Ivory Coast
  4. Transmission
    1. Multimammate Rats (Mastomys natalensis) are reservoir
      1. Contamination of food with rodent urine
    2. Person to person blood or body fluid contact
      1. Urine
      2. Feces
      3. Vomit
      4. Saliva
  5. Incubation: 1-24 days

III. Symptoms

  1. Early, Insidious symptoms
    1. Fever (100%)
    2. Chills
    3. Rigors
    4. Headache (50%)
    5. Malaise (100%)
    6. Myalgia (50%)
  2. Second week symptoms
    1. Lower Abdominal Pain
    2. Intractable Vomiting
  3. Other symptoms
    1. Tinnitus
    2. Epistaxis
    3. Bleeding Gums
    4. Maculopapular rash
    5. Cough
    6. Dizziness

IV. Signs

  1. Early
    1. Fever
    2. Flushing of face and V-neck area
    3. Pharyngitis (progressive over first week)
      1. Raised patch of whitish exudate on Tonsillar Pillar
      2. Pseudomembranes may develop
      3. Oral Ulcerations (50%)
    4. Generalized non-tender Lymphadenopathy (50%)
  2. Later
    1. Facial and neck swelling
    2. Conjunctivitis
  3. Severe, Acute Phase
    1. Systolic Blood Pressure below 90 (60-80%)
    2. Pulse Pressure less than 20
    3. Relative Bradycardia

V. Labs

  1. Complete Blood Count
    1. Hematocrit normal
    2. White Blood Cell Count low (Leukopenia)
      1. Relative Neutrophilia
  2. Erythrocyte Sedimentation Rate normal
  3. Liver Function Tests
    1. Aspartate Aminotransferase (AST, SGOT) elevated
    2. Creatinine phosphokinase (CPK) elevated
    3. Lactate Dehydrogenase (LDH) elevated
  4. Urinalysis
    1. Severe Proteinuria
  5. Lassa Virus Antibody titer
    1. Fourfold rise between acute and convalescent phase

VI. Radiology

  1. Chest XRay
    1. Basilar pneumonitis
    2. Pleural Effusions

VII. Diagnostics

  1. Electrocardiogram
    1. May show diffuse Myocardial Disease

VIII. Complications

  1. Oculogyric Crisis (rapid involuntary eye movement)
  2. Deafness
  3. Alopecia

IX. Course

  1. Illness lasts 7 to 31 days (average 12-15 days)

X. Prognosis

  1. Mortality: 8 to 52%
  2. Signs suggestive of poor prognosis or death
    1. Shock
    2. Altered Level of Consciousness
    3. Auscultated Rales
    4. Pleural Effusion
    5. Grand Mal Seizures

XI. Differential Diagnosis

  1. Hemorrhagic FeverViruses

XII. Management

  1. Supportive care
  2. Ribavirin (Virazole)
    1. See Viral Hemorrhagic Fever for protocol
    2. Appears highly effective
  3. Infusion of immune plasma from convalescent patients
  4. Isolation Procedures
    1. Respiratory isolation
    2. Blood and Body fluid precautions

XIII. References

  1. Seeyave (2015) Crit Dec Emerg Med 29(5): 13-21
  2. Wilson (1991) Harrison's PIM, Mcgraw Hill, pp. 740-1

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