Updated: 11/15/2018

Yellow Fever

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Snapshot
  • A 32-year-old woman presents to a local clinic in Nigeria. She had been working in the rainforest as part of a conservation movement and had been bitten multiple times over the past few days by mosquitos and other flying insects. Three days ago, she developed a flu-like viral illness and recently began having minor nosebleeds. She also noted that her skin looked more yellow than normal. On exam, she is jaundiced with scleral icterus. She is also noted to have hepatomegaly and gingival bleeding. Laboratory testing reveals a transaminitis and hyperbilirubinemia. She is told that she needs to be admitted for 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

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