Yellow fever is a mosquito-borne viral hemorrhagic fever caused by the yellow fever virus (YFV), a flavivirus endemic to tropical Africa and South America. It presents as a biphasic illness ranging from mild undifferentiated febrile illness to fulminant hepatorenal failure with hemorrhage, carrying a case-fatality rate of 30–60% in severe cases.[1-2] No specific antiviral therapy exists; management is entirely supportive.[1]
1. History
- Incubation period: 3–6 days after mosquito bite (Aedes or Haemagogus species)[1-2]
- Phase 1 (infection/viremic phase): Abrupt onset of high fever (up to 40°C), chills, severe headache, lumbosacral/back pain, generalized myalgias, nausea, vomiting, anorexia, dizziness, and prostration; lasts ~3 days[1-2]
- Brief remission: ≤48 hours of apparent improvement
- Phase 2 (toxic/intoxication phase): Recurrence of fever with jaundice, epigastric pain, hemorrhagic manifestations (hematemesis, melena, epistaxis, gingival bleeding, petechiae), renal insufficiency, and cardiovascular instability; occurs in ~12–15% of infected patients[1-2]
- Key HPI: Travel to endemic areas (sub-Saharan Africa, tropical South America), vaccination status, outdoor/forest exposure, timing of symptom onset relative to travel, occupational exposures[2]
- Ask about bleeding from any site, dark urine, decreased urine output, confusion, abdominal pain
2. Alarm Features
- Jaundice developing after initial febrile illness[1][3]
- Hemorrhagic manifestations: hematemesis ("coffee-grounds" or frank), melena, hematuria, petechiae, ecchymoses, oozing from puncture sites[2]
- Oliguria/anuria suggesting acute renal failure[4]
- Altered mental status, agitated delirium, seizures, or hepatic encephalopathy[5]
- Hypotension/shock refractory to fluids[4]
- Severe metabolic acidosis, hypoglycemia, hyperkalemia[4]
- Rapidly rising AST/ALT (AST >1,841 IU/L and creatinine >1.2 mg/dL independently associated with death)[6]
3. Medications
- No specific antiviral therapy is effective (ribavirin, sofosbuvir, interferon alpha all failed to improve outcomes)[1]
- Avoid aspirin and NSAIDs — elevated bleeding risk[2][7]
- Acetaminophen is preferred for fever and myalgias[2]
- In severe cases: IV proton pump inhibitors (therapeutic dose) to prevent GI bleeding[3][5]
- Prophylactic anticonvulsants when ammonia >70 μmol/L[5]
- Prophylactic antibiotics in severe hepatic insufficiency (e.g., cefotaxime + fluconazole)[8]
- YF-VAX (17D vaccine): Single subcutaneous dose of 0.5 mL for prevention; provides long-lasting immunity[9]
4. Diet
- Maintenance of nutrition and prevention of hypoglycemia are critical in severe disease[4]
- NPO or nasogastric suction may be required to prevent gastric distension and aspiration in severe cases[4]
- IV dextrose-containing fluids for hypoglycemia management
- No specific dietary triggers; hydration is essential during the febrile phase
5. Review of Systems
- GI: Nausea, vomiting, epigastric pain, hematemesis, melena, abdominal pain (pancreatitis reported in 24% of severe cases)[5]
- Renal: Decreased urine output, dark urine, flank pain
- Neurologic: Headache, photophobia, confusion, seizures, altered consciousness[5]
- Hematologic: Easy bruising, bleeding from gums, heavy menses (metrorrhagia), blood in urine[2]
- Cardiac: Palpitations, chest pain (myocardial involvement possible)[10]
- Musculoskeletal: Severe myalgias, arthralgias, back pain[2]
6. Collateral History and Family History
- Travel companions with similar symptoms (cluster of febrile illness from same endemic area)
- Vaccination history — prior YF vaccination essentially excludes wild-type disease
- Occupational exposure: forestry workers, farmers, military personnel in endemic zones[2]
- No hereditary predisposition, though neutralizing antibody response may vary by ethnicity[3]
- Social context: unvaccinated travelers, migrants from endemic regions
7. Risk Factors
- Travel to or residence in tropical Africa or South America without vaccination[2]
- Unvaccinated status (vaccine is highly effective; few breakthrough cases among 540 million doses administered)[3]
- Outdoor/sylvatic exposure in forested areas (jungle transmission cycle)[2]
- Older age — independently associated with mortality[8]
- Male sex — 80–92% of severe cases in outbreaks were male, likely reflecting occupational exposure[11-12]
- Diabetes mellitus — associated with higher case fatality (80% vs 65%)[5]
- Mosquito season and rainy periods in endemic areas
8. Differential Diagnosis
- Must-differentiate conditions in a patient with fever and jaundice from an endemic area:[2][4]
- Leptospirosis — closest mimic; also causes jaundice, hemorrhage, DIC, renal failure; distinguished by conjunctival suffusion, exposure to contaminated water, positive leptospira serology/PCR[4]
- Malaria (P. falciparum/blackwater fever) — thick/thin smear or rapid diagnostic test; can cause jaundice and renal failure but hemorrhage is uncommon[13]
- Dengue hemorrhagic fever — similar arboviral presentation; plasma leak syndrome and hemoconcentration are more characteristic; typically less hepatocellular injury; NS1 antigen/dengue serology[14-15]
- Viral hepatitis (A, B, E — especially fulminant hepatitis E in pregnancy)[4]
- Louse-borne relapsing fever (Borrelia recurrentis) — jaundice, hemorrhage, DIC[4]
- Other viral hemorrhagic fevers: Ebola, Marburg, Lassa, Crimean-Congo HF — usually without prominent jaundice[2]
- Typhoid fever, Q fever, rickettsial diseases[2]
- Surgical, drug-induced, or toxic causes of jaundice[2]
9. Past Medical History
- Prior YF vaccination (single dose provides lifelong immunity in most individuals)[3]
- Previous flavivirus infections (dengue, Zika, West Nile) — may cause serologic cross-reactivity complicating diagnosis[1]
- Immunocompromised states — relevant for vaccine eligibility and disease severity
- Chronic liver disease — may worsen hepatic outcomes
- Diabetes mellitus — higher mortality risk[5]
- Chronic kidney disease — baseline renal impairment affects prognosis
10. Physical Exam
- Vital signs: High fever (up to 40°C); Faget's sign (bradycardia relative to fever) is characteristic; hypotension in severe/toxic phase[2][4]
- Skin: Scleral and dermal icterus, petechiae, ecchymoses[2]
- HEENT: Conjunctival injection, gingival bleeding, epistaxis[2]
- Abdomen: Epigastric tenderness without hepatomegaly (notable absence of hepatic enlargement); assess for signs of pancreatitis[2][5]
- Hemorrhagic signs: Oozing from venipuncture sites, hematemesis, melena, metrorrhagia[2]
- Neurologic: Assess for encephalopathy (confusion, asterixis, agitation, stupor, coma)[4]
- Cardiovascular: Bradycardia, signs of myocardial dysfunction[10]
11. Lab Studies
- CBC: Leukopenia in first week (leukocytosis may appear in second week); thrombocytopenia[2]
- Hepatic panel: Markedly elevated AST and ALT — AST characteristically exceeds ALT (due to myocardial and skeletal muscle injury in addition to hepatic damage); hyperbilirubinemia (direct predominant)[4]
- Fatal cases: mean AST ~2,766 IU/L, ALT ~660 IU/L; ICU patients: median AST 7,000 IU/L, ALT 3,936 IU/L[4-5]
- Coagulation: Prolonged PT/INR, aPTT; decreased fibrinogen; elevated D-dimer and fibrin split products; reduced factors II, V, VII, VIII, IX, X[4][16]
- Renal function: Elevated creatinine and urea (creatinine >1.2 mg/dL associated with death)[6]
- Ammonia: Elevated in hepatic encephalopathy (>70 μmol/L triggers anticonvulsant prophylaxis)[5]
- Lactate, ABG: Metabolic acidosis in severe cases[5][11]
- MELD score can be calculated to assess severity[17]
- Mortality predictors: Older age, neutrophil count ≥4,000/mL, elevated AST, viral load ≥5.1 log₁₀ copies/mL (100% mortality when both neutrophil and viral load thresholds exceeded)[8]
12. Imaging
- Not routinely diagnostic for yellow fever
- CT head: Indicated if altered mental status, seizures, or signs of intracranial hypertension[8]
- Abdominal ultrasound/CT: May reveal hepatomegaly (though classically absent), pancreatitis, or renal changes
- Chest X-ray: Assess for pulmonary edema or ARDS in severe cases
- Transcranial Doppler and optic nerve sheath measurement if intracranial hypertension suspected[8]
13. Special Tests
- RT-PCR for YFV RNA: Best performed early in illness (viremic phase, first ~5 days); by the time jaundice appears, viremia may be undetectable[1]
- Serology: YFV-specific IgM and IgG by ELISA; cross-reactivity with other flaviviruses requires confirmation by plaque reduction neutralization test (PRNT)[1][7]
- Virus isolation: Possible via cell culture (AP61 cells most sensitive) or suckling mouse inoculation — performed at reference laboratories only[4]
- Antigen-detection ELISA: Sensitivity ~69%, specificity ~100% under field conditions[4]
- Histopathology (liver biopsy/autopsy): Midzonal hepatocellular necrosis (pathognomonic), apoptotic hepatocytes (Councilman bodies), microvesicular steatosis, minimal inflammatory infiltrate[7][18]
- Thromboelastography for coagulopathy assessment in ICU[8]
- Contact CDC Arboviral Diseases Branch (970-221-6400) or state health department for diagnostic assistance[1]
14. ECG
- Sinus bradycardia in 24% of patients (Faget's sign)[10]
- ST-T wave abnormalities reflecting myocardial injury[4]
- Significant ECG abnormalities in 52% of mild/moderate and 77% of severe cases[10]
- Holter monitoring: 44% of patients had mean HR <60 bpm[10]
- Echocardiography may reveal LV dysfunction (6%) and myocardial hyper-refringent texture suggestive of infiltration (18–27%)[10]
- Rare: Acute myocarditis confirmed on MRI or necropsy[10]
15. Assessment
- Yellow fever presents as a biphasic illness with an initial nonspecific febrile phase followed by a brief remission and then a potentially fatal toxic phase in ~12–15% of symptomatic patients.[1-2] The toxic phase is characterized by the triad of jaundice, hemorrhage, and renal failure. The disease is highly hepatotropic, with midzonal hepatocellular necrosis being pathognomonic.[18]
Severity stratification
- Mild: Self-limited fever and headache (majority of symptomatic cases)
- Moderate: Fever with jaundice, mild transaminase elevation, no hemorrhage
- Severe: Hepatorenal failure, hemorrhagic diathesis, encephalopathy, shock — CFR 30–67% even with ICU care[1][5]
- Complications: Fulminant hepatic failure, DIC, necrohemorrhagic pancreatitis, seizures/status epilepticus, ARDS, severe metabolic acidosis, secondary bacterial infections[5]
16. Treatment Plan
- No antiviral therapy exists; treatment is entirely supportive:[1-2]
Initial stabilization
- IV fluid resuscitation (individualized; avoid volume overload — patients do not respond dramatically to fluids unlike dengue)[4][19]
- Norepinephrine early for persistent hypotension[19]
- Acetaminophen for fever; strictly avoid aspirin and NSAIDs[2][7]
ICU management for severe disease
- IV PPI (therapeutic dose) to prevent GI hemorrhage[5]
- Anticonvulsant prophylaxis when ammonia >70 μmol/L (reduced seizure frequency from 28% to 17%)[5]
- Early renal replacement therapy — 73% of severe cases required RRT[5]
- Blood products: FFP, cryoprecipitate, platelets guided by hemorrhage severity and coagulation parameters; restrict platelet transfusion per consensus[8][19]
- Plasma exchange: Early institution recommended in severe cases[3][19]
- Prophylactic antibiotics for severe hepatic insufficiency (e.g., cefotaxime + fluconazole)[8]
- Liver transplant team consultation when factor V <50%, encephalopathy, INR >2.5, or ammonia >70 μmol/L[8]
- Strict intra-abdominal pressure monitoring[19]
- Mosquito isolation during viremic phase to prevent transmission[1]
Prevention
- YF-VAX vaccine (live attenuated 17D): Single 0.5 mL subcutaneous dose ≥10 days before travel; provides lifelong immunity for most individuals[1][9]
17. Disposition
- Admit to ICU: Any evidence of toxic phase — jaundice, hemorrhage, renal insufficiency, coagulopathy, encephalopathy, hemodynamic instability[8][19]
- Admit to monitored bed: Confirmed or suspected YF with moderate symptoms, rising transaminases, or coagulopathy
- Observation: Mild febrile illness with travel history and pending diagnostics; serial labs q8h recommended[8]
- Specialist consultation triggers: Hepatology/liver transplant (factor V <50%, encephalopathy), nephrology (AKI requiring RRT), hematology (refractory coagulopathy), infectious disease, critical care[8]
- Public health notification: YF is a nationally notifiable disease — report immediately to state/local health department[1]
18. Follow Up / Return Precautions
- Survivors: Transaminase elevations may persist up to 2 months after onset; follow hepatic and renal function serially[2]
- Discharge criteria: Absence of clinical symptoms with normal or progressively improving laboratory values[8]
- Return precautions: Seek immediate care for recurrence of fever, jaundice, dark urine, bleeding from any site, confusion, decreased urine output, severe abdominal pain
- Counseling: Lifelong immunity after natural infection; mosquito bite prevention during viremic phase; vaccination of close contacts/household members traveling to endemic areas
- Expected recovery: Survivors of mild disease recover fully; survivors of severe disease may have prolonged convalescence with fatigue and hepatic recovery over weeks to months
- Cardiac follow-up may be warranted given evidence of myocardial involvement in a significant proportion of patients[10]
References
1. Yellow Fever. — J. Erin Staples and Kevin O’Laughlin CDC Yellow Book. 2025.
2. Yellow Fever Vaccine: Recommendations of the Advisory Committee on Immunization Practices (ACIP). — J. Erin Staples MD PhD, Mark Gershman MD, Marc Fischer MD Advisory Committee on Immunization Practices (2010). 2010.
3. Prevention of Yellow Fever in Travellers: An Update. — Reno E, Quan NG, Franco-Paredes C, et al. The Lancet. Infectious Diseases. 2020.
4. Yellow Fever: An Update. — Monath TP. The Lancet. Infectious Diseases. 2001.
5. Severe Yellow Fever in Brazil: Clinical Characteristics and Management. — Ho YL, Joelsons D, Leite GFC, et al. Journal of Travel Medicine. 2019.
6. Yellow Fever: Factors Associated With Death in a Hospital of Reference in Infectious Diseases, São Paulo, Brazil, 2018. — Ribeiro AF, Cavalin RF, Abdul Hamid Suleiman JM, et al. The American Journal of Tropical Medicine and Hygiene. 2019.
7. Histopathology of vaccine‐preventable diseases. — Solomon IH, Milner DA. Histopathology. 2017.
8. Predictors of Mortality in Patients With Yellow Fever: An Observational Cohort Study. — Kallas EG, D'Elia Zanella LGFAB, Moreira CHV, et al. The Lancet. Infectious Diseases. 2019.
9. FDA Drug Label. — Food and Drug Administration (DailyMed)..
10. Cardiac Involvement by Yellow Fever(from the PROVAR+ Study). — Paixão GMM, Nunes MCP, Beato BDVG, et al. The American Journal of Cardiology. 2019.
11. Clinical Profiles and Factors Associated With Mortality in Adults With Yellow Fever Admitted to an Intensive Care Unit in Minas Gerais, Brazil. — de Ávila RE, José Fernandes H, Barbosa GM, et al. International Journal of Infectious Diseases : IJID : Official Publication of the International Society for Infectious Diseases. 2020.
12. Yellow Fever: Profile of Cases and Factors Associated With Death in a Hospital in the State of Rio De Janeiro, 2017-2018. — Escosteguy CC, Pereira AGL, Marques MRVE, et al. Revista De Saude Publica. 2019.
13. Malaria: Prevention, Diagnosis, and Treatment. — Shahbodaghi SD, Rathjen NA. American Family Physician. 2022.
14. Dengue in Travelers. — Wilder-Smith A, Schwartz E. The New England Journal of Medicine. 2005.
15. Dengue. — Simmons CP, Farrar JJ, Nguyen vV, Wills B. The New England Journal of Medicine. 2012.
16. Consumptive Coagulopathy of Severe Yellow Fever Occurs Independently of Hepatocellular Tropism and Massive Hepatic Injury. — Bailey AL, Kang LI, de Assis Barros D'Elia Zanella LGF, et al. Proceedings of the National Academy of Sciences of the United States of America. 2020.
17. Systems Immunology Approaches to Understanding Immune Responses in Acute Infection of Yellow Fever Patients. — Gonçalves ANA, Costa PR, Thomazella MV, et al. Journal of Medical Virology. 2024.
18. A Review of Arboviral‐Induced Liver Damage: Acute Manifestations and Speculative Links to Chronic Inflammation. — Wang B, Wang Z. Reviews in Medical Virology. 2025.
19. Colombian Consensus on the Care of Critically Ill Patients With Suspected or Confirmed Severe Yellow Fever. — Forero-Delgadillo AJ, Morales-Olivera JA, Celis-Guzmán JF, et al. Lancet Regional Health. Americas. 2025.