Pathogenesis of Yellow Fever
Viral Characteristics and Infection
- Yellow fever virus is an RNA virus belonging to the genus Flavivirus, antigenically related to West Nile virus, St. Louis encephalitis virus, and Japanese encephalitis virus, as reported by the Centers for Disease Control and Prevention 1, 2.
- Following mosquito inoculation, the virus enters the bloodstream and replicates in target tissues, producing high levels of viremia that peak shortly before fever onset and persist for 3-5 days, according to the Centers for Disease Control and Prevention 1, 3.
- The incubation period ranges from 3-6 days before clinical manifestations appear, as stated by the World Health Organization 4, 5.
Organ System Pathology
- Massive hepatocyte infection and destruction leads to jaundice, a hallmark of severe disease, with a case-fatality ratio of 20-50% in patients with hepatorenal dysfunction, as reported by the Centers for Disease Control and Prevention 4, 5, 6.
- Renal failure develops in severe cases through direct viral infection of renal tubular cells and immune-mediated damage, resulting in a case-fatality ratio of 20-50% in patients with hepatorenal dysfunction, according to the Centers for Disease Control and Prevention 4, 5, 6.
- Thrombocytopenia develops through both consumptive processes and direct viral effects on megakaryocytes, contributing to the coagulopathy and hemorrhagic manifestations of severe disease, as stated by the World Health Organization 4, 5.
Clinical Spectrum and Disease Progression
- Approximately 15% of symptomatic patients progress to severe disease with jaundice, hemorrhagic manifestations, and multisystem organ failure, with a fatality rate of approximately 20% overall, reaching 20-50% in those with severe disease, as reported by the Centers for Disease Control and Prevention 4, 5, 6.
- The majority of YFV infections remain asymptomatic or produce only mild, undifferentiated febrile illness, while symptomatic disease manifests abruptly with fever, prostration, headache, photophobia, lumbosacral pain, extremity pain, epigastric pain, anorexia, and vomiting, according to the World Health Organization 4, 5, 6.