Yellow Fever Virus

Snapshot

• A 40-year-old man presents to a hospital after flying from sub-Saharan Africa. He had been on a safari and had sustained multiple mosquito bites. He had not gotten his necessary vaccines, as the trip was planned last-minute. For the past 2 days, he has had fevers, chills, myalgias, and some vomiting. After landing, he had an episode of bloody vomiting. On physical exam, he has a high fever. He also has gingival bleeding, jaundice, and scleral icterus. On abdominal exam, he has hepatosplenomegaly. He is admitted for supportive care and close monitoring.

Introduction

• Classification
  • yellow fever virus
    • a positive-stranded, linear RNA virus
    • a flavivirus and arbovirus with icosahedral capsid
    • transmitted by Aedes mosquito
    • reservoir is human or monkey
• Epidemiology
  • incidence
    • endemic in South America and Africa
  • risk factors
    • exposure to endemic areas
    • mosquito bites
• Pathogenesis
  • the virus spreads via blood
  • it infects the liver
    • liver cells die via apoptosis
    • coagulopathy occurs due to loss of hepatic synthesis of clotting factors
• Associated conditions
  • hemorrhagic fever
• Prevention
  • live-attenuated virus vaccine
    • given at age 9-12 months in endemic areas
    • given 10 days prior to travel to endemic areas
• Prognosis
  • most patients recover without complications
• however, in severe cases, mortality rate is up to 60%    

Presentation

• Symptoms 
  • most patients are asymptomatic
  • if symptomatic
    • flu-like prodrome
    • headache
    • myalgias
    • nausea
    • black vomitus
• Physical exam
  • high fever
  • jaundice
  • scleral icterus
  • hepatomegaly
  • minor hemorrhage
    • epistaxis
    • mucosal bleeding
• melena

Studies

• Labs
  • diagnostic
    • reverse transcriptase-polymerase chain reaction
    • serology with enzyme-linked immunosorbent assay
  • transaminitis (AST > ALT)
  • elevated prothrombin and partial thromboplastin times
  • hyperbilirubinemia
• Guaiac stool testing
  • occult blood
• Liver biopsy
  • Councilman bodies 
    • eosinophilic apoptotic globules
  • typically found on autopsy
• Making the diagnosis
• most cases are clinically diagnosed, especially in those who have recently traveled to an endemic area

Differential

• Dengue fever 
  • distinguishing factor
    • may also be hemorrhagic but does not affect the liver
    • will not present with jaundice, scleral icterus, and hepatomegaly
• Chikungunya 
  • distinguishing factor
• typically does not present with hemorrhage

Treatment

• Conservative
  • supportive care
    • indication
      • all patients
    • modalities
      • rehydration
      • close monitoring
• pain control

Complications

• Shock
• Death
• Prolonged weakness and fatigue