[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [RNA arboviruses](https://durgical.com/en/microbiology/groups/rna-arboviruses/) › Yellow fever virus [Microbiology](https://durgical.com/en/microbiology/) · [RNA arboviruses](https://durgical.com/en/microbiology/groups/rna-arboviruses/) # Yellow fever virus - Virus - Enveloped - Exam priority: high A flavivirus kept alive by monkeys and forest mosquitoes. It can cause jaundice, bleeding and organ failure; one vaccine dose protects for life. Updated 2026-11-01 Also called: YFV ## Key points - Flavivirus with a sylvatic cycle (monkeys, Haemagogus, Sabethes) and an urban cycle (Aedes aegypti) - Hepatitis with midzonal necrosis and Councilman bodies - Toxic phase: jaundice, black vomit, kidney failure; Faget sign - Live 17D vaccine, single dose, lifelong; in Colombia's PAI ## At a glance **Shape** Spherical, icosahedral capsid **Genome** Single-stranded, positive-sense RNA **Envelope** Enveloped **Family** Flaviviridae, genus Orthoflavivirus **Size** About 40 to 50 nm ## Morphology - Enveloped virus with protein E; a single serotype - The prototype flavivirus that names the family (flavus, yellow) ## Transmission - Sylvatic cycle: Haemagogus and Sabethes mosquitoes among monkeys; humans are infected on entering the forest - Intermediate cycle: semi-domestic mosquitoes in rural areas near forest - Urban cycle: Aedes aegypti from person to person, the highest epidemic risk **Reservoir:** Non-human primates (howler monkeys, among others); Mosquitoes, which stay infected for life **Vector:** Haemagogus and Sabethes (sylvatic); Aedes aegypti (urban) ### Isolation precautions What the care team adds to standard precautions. - Standard ## Virulence factors - Liver tropism: midzonal lobular necrosis with Councilman (apoptotic) bodies - Liver damage causes jaundice and coagulopathy - Kidney and heart injury and shock in the toxic phase ## Diseases it causes - Yellow fever: mild form and toxic phase with jaundice, bleeding and kidney failure [Yellow fever →](https://durgical.com/en/conditions/yellow-fever/) ## Clinical picture - Many infections are mild: fever, headache, myalgia, nausea - Faget sign: high fever with a relatively slow pulse - Brief remission and then, in a share of cases, a toxic phase with jaundice, bleeding (black vomit), kidney failure and shock - About half of patients in the toxic phase die within 7 to 10 days ## Diagnosis - RT-PCR on blood early in illness - IgM by ELISA and neutralization tests later - Very high transaminases and bilirubin, albuminuria - Vaccination and forest travel history; cross-reaction with other flaviviruses ## Treatment There is no specific antiviral: care is supportive in a unit able to manage liver and kidney failure and bleeding. Aspirin and NSAIDs are avoided. Drug class only; doses and regimens are set by the clinician from the current guideline. ## Prevention - Live attenuated vaccine (17D strain): one dose gives lifelong protection - Bite protection and Aedes aegypti control in cities - Epizootic surveillance: monkey deaths warn of virus circulation **Vaccine:** Live attenuated 17D vaccine, single dose with lifelong immunity; it is in Colombia's childhood PAI schedule and offered to people living in or travelling to risk areas. It is not advised under 9 months, in pregnancy (except in outbreaks), with severe egg allergy or severe immunosuppression. Some countries require the international certificate of vaccination from travellers. ## In Colombia Colombia is one of the endemic countries of the Americas, with risk in the Orinoquía, Amazon, Catatumbo, Sierra Nevada and inter-Andean valleys. From 2024 a high-fatality outbreak centred on Tolima led to stepped-up vaccination. Monkey deaths and human cases are immediately notifiable to SIVIGILA. ## Memory aid Yellow from the liver, black from the vomit: the disease paints the patient in the colours of its toxic phase. ## Test yourself Think of the answer, then tap the question to see it. ## What is the main transmission cycle of yellow fever in the Americas? The sylvatic cycle: Haemagogus and Sabethes mosquitoes pass the virus among monkeys, and people are infected when they enter the forest or its edges. ## Which liver histology finding is classic for yellow fever? Midzonal lobular necrosis with Councilman bodies (apoptotic hepatocytes). ## How many vaccine doses give lifelong protection? A single dose of the live attenuated 17D vaccine; WHO says no booster is needed. ## What is the Faget sign? High fever with a relatively slow pulse, described in yellow fever. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/yellow-fever-virus/) ## Related - [Dengue virus](https://durgical.com/en/microbiology/dengue-virus/) ## Related conditions - [Yellow fever](https://durgical.com/en/conditions/yellow-fever/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. [← Back to the group: RNA arboviruses](https://durgical.com/en/microbiology/groups/rna-arboviruses/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Yellow fever](https://www.who.int/news-room/fact-sheets/detail/yellow-fever) (World Health Organization (WHO), 2025); [Yellow Fever](https://www.paho.org/en/topics/yellow-fever) (Pan American Health Organization (PAHO), 2025); [Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions](https://www.cdc.gov/infection-control/hcp/isolation-precautions/appendix-a-type-duration.html) (CDC, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/yellow-fever-virus/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/yellow-fever-virus/