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