Yellow Fever

Key Features

• Zoonotic viral infection transmitted by the bite of the Aedes mosquito

• Found in tropical and subtropical South America and Africa

• Incubation period is typically 3–6 days

• Adults and children equally susceptible

• Mortality rate of severe disease is 20–50%

Clinical Findings

• Mild form (85%)

  • Fevers

  • Malaise

  • Retroorbital pain

  • Nausea

  • Photophobia

  • Bradycardia

• Severe form (15%)

  • Begins with the same symptoms as the mild form of the disease

  • Then, after initial remission of symptoms, a toxic phase ensues with fever, bradycardia, hypotension, jaundice, delirium, hemorrhage

Diagnosis

• Leukopenia, elevated liver enzymes, and bilirubin can occur

• Proteinuria is present and usually disappears completely with recovery

• Bleeding dyscrasias with elevated prothrombin and partial thromboplastin times, decreased platelet count, and presence of fibrin-split products, can also occur

• In the early stages of the disease (up to 10 days), diagnosis is confirmed if yellow fever virus RNA is detected by (RT-PCR) in blood from a person with no history of recent yellow fever vaccination

• Presence of yellow fever virus-specific IgM antibody and negative ELISA panel for other relevant flaviviruses confirm the diagnosis

• If ELISA is positive for other flaviviruses, plaque reduction neutralization assay, which measures the titer of the neutralizing antibodies in the serum towards the infecting virus, should be done

Treatment

• Supportive measures, including analgesia and hydration

• No specific antiviral therapy

• Prevention

  • A highly effective and safe vaccine is available and should be used when living or traveling to endemic areas

  • Mosquito control measures