Yellow Fever in New Zealand: Symptoms, Causes & Treatment | aihealz
Tropical Medicinesevere
Yellow Fever.Care & specialists in New Zealand
In New Zealand, yellow Fever is managed by tropical medicines. Yellow fever is an acute viral hemorrhagic fever caused by a flavivirus transmitted by Aedes and Haemagogus mosquitoes in tropical Africa and South America. WHO estimates 84,000-170,000 severe cases and 29,000-60,000 deaths each year despite the availability of a highly effective single-dose live-attenuated vaccine licensed since 1937.
aliases · Yellow fever· Vomito negro / Black vomit· Fièvre jaune· Febre amarela· reviewed May 14, 2026
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Reviewed by AIHealz Medical Editorial Board · Tropical MedicineLast reviewed May 13, 2026
Yellow fever (ICD-10: A95) is an acute viral hemorrhagic fever caused by yellow fever virus (YFV), a single-stranded positive-sense RNA virus in the Flaviviridae family that is closely related to dengue, West Nile, and Zika viruses. The virus is transmitted to humans through bites of infected female mosquitoes in three distinct transmission cycles: jungle (sylvatic) yellow fever between forest mosquitoes (Haemagogus and Sabethes in the Americas; Aedes africanus in Africa) and non-human primates, with humans occasionally infected when entering the forest; intermediate (savannah) yellow fever in moist savannah regions of Africa where multiple Aedes species transmit virus between humans and monkeys in small villages; and urban yellow fever, in which Aedes aegypti transmits virus among humans in densely populated cities and produces large explosive outbreaks. The first phase of disease (period of infection) follows a 3-6 day incubation and consists of fever, headache, myalgia, backache, nausea, and conjunctival injection over 3-4 days. Roughly 85% of symptomatic patients recover at this point.
key facts
Prevalence
Estimated 84,000-170,000 severe cases and 29,000-60,000 deaths per year (WHO 2024)
Demographics
47 countries endemic in Africa, 13 in Central and South America; over 90% of cases reported from Africa
Avg. age
Working-age adults dominate documented case counts; vaccine coverage in children under 5 averages 50-70% in endemic countries
Global cases
Case-fatality rate 30-60% in those with severe disease; over 1 billion people targeted by WHO EYE strategy by 2026
Specialist
Tropical Medicine
§ 02
How you might notice it
The key symptoms of Yellow Fever are: Sudden onset of fever above 39 °C with rigors, severe headache (often retro-orbital and frontal), and back pain 3-6 days after a mosquito bite in an endemic region., Severe muscle pain particularly in the back and legs, malaise, and prostration during the first 3-4 days (period of infection)., Conjunctival injection without exudate, facial flushing, and a tongue with red edges and white furred center — historical clinical descriptions., Relative bradycardia despite high fever (Faget's sign), an early clue that distinguishes yellow fever from many other tropical febrile illnesses., Apparent improvement on day 3-4 with defervescence and reduced symptoms — the brief remission., Return of fever, vomiting (sometimes with frank hematemesis — historic 'vomito negro' or 'black vomit'), and jaundice 24-48 hours after remission, marking the period of intoxication., Worsening jaundice and right-upper-quadrant abdominal pain from acute hepatic injury..
01Sudden onset of fever above 39 °C with rigors, severe headache (often retro-orbital and frontal), and back pain 3-6 days after a mosquito bite in an endemic region.
02Severe muscle pain particularly in the back and legs, malaise, and prostration during the first 3-4 days (period of infection).
03Conjunctival injection without exudate, facial flushing, and a tongue with red edges and white furred center — historical clinical descriptions.
04Relative bradycardia despite high fever (Faget's sign), an early clue that distinguishes yellow fever from many other tropical febrile illnesses.
§ 03
How it’s diagnosed
diagnosis
Diagnosis combines compatible clinical illness, exposure history (recent travel to or residence in a yellow fever transmission zone), and laboratory confirmation. Routine bloods in the toxic phase typically show leukopenia followed by neutrophilia, very high transaminases (AST often greater than ALT and rising into the thousands), conjugated and unconjugated hyperbilirubinemia, prolonged prothrombin time, thrombocytopenia, and rising creatinine. The specific diagnostic standard is detection of viral RNA by RT-PCR within the first 7-10 days of illness on blood or, in fatal cases, post-mortem liver tissue. Yellow fever IgM antibody is detectable from day 5-7 of illness and persists for months to years; cross-reactivity with other flaviviruses (dengue, Zika, Japanese encephalitis, West Nile) is significant and requires plaque-reduction neutralization testing (PRNT) at reference laboratories for confirmation. Vaccinated travellers retain IgG for life, so serology alone cannot diagnose acute infection in vaccinated patients without paired sera demonstrating a rise. Detection of yellow fever viral antigen (NS1) and immunohistochemistry of liver tissue (showing characteristic mid-zonal hepatocyte necrosis with Councilman bodies — eosinophilic apoptotic hepatocyte remnants) is a hallmark in post-mortem confirmation. Differential diagnosis is broad and includes other viral hemorrhagic fevers (Ebola, Lassa, Marburg, dengue, Crimean-Congo), severe malaria, leptospirosis, viral hepatitis (especially fulminant hepatitis A and E), severe sepsis, and toxic exposures. All suspected cases require notification to public-health authorities.
Key tests
01
RT-PCR for yellow fever virus RNAConfirms acute infection during the first 7-10 days of illness
02
Yellow fever IgM antibody (ELISA)Detects recent infection from day 5-7 of illness
03
§ 04
Treatment & cost
medical treatments
✓Aggressive intravenous fluid and electrolyte resuscitation
✓Renal replacement therapy (hemodialysis or continuous renal replacement)
✓Hepatic supportive care (glucose, vitamin K, lactulose, N-acetylcysteine)
surgical options
Liver transplantation in fulminant yellow fever hepatitisCase-series survival approximately 40-70% in carefully selected patients; very limited published experience
§ 05
Causes & risk factors
known causes
Yellow fever virus (YFV) transmitted by Aedes aegypti in the urban cycle
Aedes aegypti is the principal urban vector and feeds on humans during daytime. Urban transmission cycles support explosive outbreaks in densely populated cities and account for the historical global spread of yellow fever via shipping during the 18th-19th centuries.
Yellow fever virus transmitted by Haemagogus and Sabethes mosquitoes in the South American sylvatic cycle
Forest canopy mosquitoes (Haemagogus janthinomys, Sabethes chloropterus) transmit YFV between non-human primates and humans entering forest areas for work, hunting, or recreation. Drives sporadic cases and outbreaks in Brazil, Bolivia, Peru, Venezuela, Colombia, and adjacent countries.
Yellow fever virus transmitted by Aedes africanus and other Aedes species in the African sylvatic and intermediate cycles
Aedes africanus maintains the forest cycle between monkeys and humans in tree canopies. Aedes furcifer-taylori, Aedes luteocephalus, and other Aedes species drive intermediate transmission in moist savannah regions of Africa where humans live in villages near forest edges.
Insufficient vaccination coverage in endemic populations and travellers
Yellow fever vaccine has been licensed since 1937 and provides lifelong immunity in over 95% of recipients. Outbreaks recur where vaccine coverage falls below 60-80%, including during stock-outs, vaccine hesitancy, conflict, and rapid urbanization. Unvaccinated travellers to endemic regions remain a documented source of imported cases.
Ecological and demographic change
Deforestation, urban expansion into forest, climate-change-driven extension of Aedes vector range, and rapid urbanization create new conditions for both sylvatic and urban transmission. The 2017-2019 Brazilian sylvatic outbreak followed monkey die-offs in regions long considered low-risk.
risk factors
§ 06
Living with it
01Receive a single dose of 17D yellow fever vaccine at least 10 days before travel to or residence in an endemic country.
02Carry the International Certificate of Vaccination or Prophylaxis (yellow card) for cross-border travel; many countries require it for entry from yellow-fever-endemic regions.
03Use DEET-, picaridin-, or IR3535-based insect repellent during daytime in endemic regions; Aedes aegypti bites during the day.
04Sleep under insecticide-treated bed nets and stay in screened or air-conditioned accommodation where Aedes density is high.
05Eliminate standing water around dwellings (tyres, flower pots, water containers) where Aedes mosquitoes breed.
06Participate in mass preventive vaccination campaigns where offered.
07Maintain ongoing surveillance for monkey die-offs and febrile illness in endemic regions and report suspected cases promptly.
recommended foods
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When to seek help
why see a tropical medicine
Suspected yellow fever requires urgent evaluation by infectious disease and intensive care services. Severe disease (toxic phase) demands ICU-level care with hepatology and nephrology support. Travel medicine clinics deliver pre-travel vaccination and certification.
03Disseminated intravascular coagulation with severe hemorrhage.
04Septic shock and secondary bacterial infections during prolonged ICU stay.
05Yellow-fever-vaccine-associated viscerotropic disease (YEL-AVD) — rare (1 per 100,000-400,000) but with high mortality, especially in adults over 60.
06Yellow-fever-vaccine-associated neurotropic disease (YEL-AND) — rare immune-mediated CNS reaction usually with good recovery.
Asymptomatic infectionRoughly 50% of infections produce no symptoms; recognized only by serology in outbreak investigations.
Mild yellow fever (period of infection only)Approximately 30-40% of symptomatic patients have a single 3-4 day febrile illness with headache, myalgia, conjunctival injection, and bradycardia despite fever (Faget's sign), then recover.
Severe yellow fever (period of intoxication)Approximately 15% of symptomatic patients enter the toxic phase after a brief remission: jaundice, hemorrhage, vomiting (sometimes hematemesis — 'black vomit'), renal failure, hepatic encephalopathy. Mortality 30-60%.
Hemorrhagic yellow feverSevere end of the spectrum with disseminated intravascular coagulation, gastrointestinal bleeding, epistaxis, gum bleeding, and ecchymoses; classical historical phenotype.
Sylvatic (jungle) yellow feverTransmission cycle between forest mosquitoes and non-human primates with occasional human spillover. Dominates South American transmission and accounts for sporadic and outbreak cases in Bolivia, Brazil, Peru, Colombia, and Venezuela.
Urban yellow feverAedes aegypti-mediated person-to-person transmission in dense human populations; produces explosive epidemics. Most recently re-established in Luanda, Angola in 2015-2016 with imported cases reaching China for the first time.
Living with Yellow Fever
Timeline
Mild yellow fever (period of infection only): full recovery within 1-2 weeks. Severe yellow fever survivors: hospital stay typically 2-3 weeks; full convalescence over 1-3 months. Liver function normalizes over 4-12 weeks; renal function over 4-8 weeks. Fatigue and reduced exercise tolerance can persist for several months after severe disease.
Lifestyle
01Follow medical advice and travel-clinic instructions about vaccination, boosters, and certification.
02Stay in screened or air-conditioned accommodation during travel to high-risk areas.
03Wear long-sleeved shirts and long trousers in endemic regions, particularly during daytime.
04Avoid the toxic-phase pitfalls — no aspirin or NSAIDs during a febrile tropical illness.
05Report any febrile illness within 14 days of travel from an endemic region to a clinician promptly.
06Continue regular medical follow-up if you have had a documented yellow fever vaccine adverse event; future live-vaccine decisions will need expert input.
Daily management
01Monitor temperature and report relapse after apparent improvement immediately.
02Drink at least 2-3 L of fluids per day to support kidney recovery.
Complementary approaches
Investigational antivirals (sofosbuvir, favipiravir, TY014 monoclonal antibody)Compassionate-use case reports and early-phase trials. No approved antiviral for yellow fever as of 2026; treatment remains supportive.
Choosing a doctor
Pre-travel vaccination requires a designated yellow fever vaccination centre that can issue the International Certificate of Vaccination or Prophylaxis (yellow card). For suspected disease, seek care at a national reference laboratory or tertiary infectious disease unit.
Patient support resources
WHO Yellow Fever →Global epidemiology, EYE strategy progress, vaccination policy, and outbreak situation reports.
Yellow fever is an acute viral hemorrhagic disease caused by a flavivirus transmitted by Aedes and Haemagogus mosquitoes in tropical Africa and South America. Most infections are mild or asymptomatic, but about 15% of symptomatic cases develop a toxic phase with jaundice, kidney failure, and bleeding, with 30-60% mortality.
How is yellow fever spread?▾▴
Yellow fever virus is transmitted to humans by bites of infected female mosquitoes. Aedes aegypti drives urban epidemics, while Haemagogus and Sabethes mosquitoes drive sylvatic (jungle) transmission between primates and humans in South America. The disease is not spread directly person-to-person.
What are the symptoms of yellow fever?▾▴
Symptoms begin 3-6 days after a bite with sudden fever, headache, muscle and back pain, nausea, and conjunctival injection. About 15% progress after a brief remission to the toxic phase with jaundice, severe vomiting (sometimes black vomit), bleeding, and acute kidney injury, with high mortality.
Is yellow fever curable?▾▴
There is no specific antiviral therapy for yellow fever; treatment is entirely supportive. Most patients recover with rest, fluids, and observation. Severe disease requires intensive care with renal replacement therapy, blood product support, and hepatic supportive care. The most effective intervention is prevention through vaccination.
Where is yellow fever found?▾▴
Yellow fever is endemic in 47 countries in tropical Africa and 13 in Central and South America. Over 90% of cases are reported from Africa, with Nigeria, Democratic Republic of Congo, Ethiopia, and Sudan accounting for the largest burdens. The disease is not found in Asia or Australia despite Aedes aegypti's presence.
Do I need a yellow fever vaccine for travel?▾▴
Many countries require proof of yellow fever vaccination for entry of travellers arriving from endemic regions. WHO recommends vaccination for all travellers aged 9 months and older going to endemic countries. Vaccinate at least 10 days before travel. Check current country-specific requirements before your trip.
How long does yellow fever vaccine protect you?▾▴
A single dose of 17D yellow fever vaccine produces protective antibody in over 95% of recipients within 10 days and provides lifelong protection per WHO 2013 position. Some special populations (HIV-positive, vaccinated during pregnancy, post-hematopoietic stem-cell transplant) may benefit from booster doses.
What are yellow fever vaccine side effects?▾▴
Most recipients experience only mild side effects: low-grade fever, headache, or injection-site soreness for a few days. Rare serious events include anaphylaxis (1 per 130,000-250,000) and vaccine-associated viscerotropic disease (1 per 100,000-400,000, mostly in adults over 60). Vaccinate at designated centres with pre-vaccination assessment.
Who should not get the yellow fever vaccine?▾▴
Contraindications include severe egg allergy, severe immunosuppression (advanced HIV, chemotherapy, transplantation), thymic disorders, and infants under 6 months. Pregnancy is a relative contraindication — vaccinate only if travel to high-risk areas cannot be deferred. Adults over 60 require additional pre-vaccination evaluation.
How long does yellow fever last?▾▴
The period of infection lasts 3-4 days. About 85% of symptomatic patients recover at this stage. The 15% who enter the toxic phase have a critical 7-10 day course with high mortality; survivors typically need 2-6 weeks for full convalescence. There is no chronic infection.
What is the toxic phase of yellow fever?▾▴
The toxic phase is a return of severe illness 24-48 hours after apparent recovery in roughly 15% of symptomatic patients. It features jaundice, severe vomiting (sometimes hematemesis), kidney failure, mucocutaneous bleeding, and hepatic encephalopathy. Mortality is 30-60% even with intensive care.
Is yellow fever the same as hepatitis?▾▴
No, although yellow fever can cause acute viral hepatitis with jaundice and very high transaminases. Yellow fever is caused by a flavivirus transmitted by mosquitoes and is vaccine-preventable. Viral hepatitis (A, B, C, D, E) is caused by different unrelated viruses with different transmission routes and treatments.
Can yellow fever be treated with antibiotics?▾▴
No. Yellow fever is caused by a virus, so antibiotics have no direct effect on the disease. Empirical antibiotics are sometimes used to treat secondary bacterial infections during severe yellow fever, but treatment of the underlying viral disease remains supportive.
How is yellow fever diagnosed?▾▴
Diagnosis uses RT-PCR on blood within the first 7-10 days of illness, yellow fever IgM serology from day 5-7 onwards, and confirmatory plaque-reduction neutralization testing for definitive diagnosis. Post-mortem liver histology shows characteristic mid-zonal necrosis with Councilman bodies.
Is yellow fever contagious?▾▴
Yellow fever does not spread directly from person to person under normal circumstances. Transmission requires an infected mosquito vector. Rare laboratory-acquired cases and breast-milk transmission to infants have been documented. Standard infection-control measures are still applied to confirmed cases in hospitals.
Why is it called yellow fever?▾▴
The name 'yellow fever' refers to the jaundice that develops in the toxic phase, giving the skin and eyes a yellow color. Spanish colonial chroniclers used the term 'fiebre amarilla' from the 17th century. In Brazil and parts of Latin America the disease was historically called 'vomito negro' (black vomit) for its hemorrhagic feature.
Can you get yellow fever twice?▾▴
Recovery from yellow fever produces lifelong immunity, so reinfection is essentially unheard of. The vaccine likewise produces lifelong protection in over 95% of recipients per WHO 2013 position. There is no chronic carrier state.
Is yellow fever a major problem in 2026?▾▴
Yellow fever remains a significant global health threat. WHO estimates 84,000-170,000 severe cases per year. Recent outbreaks in Angola (2015-2016), DRC (2016), Brazil (2017-2019), and Nigeria (2017-2020) have triggered emergency vaccination campaigns. The WHO EYE strategy aims to protect 1 billion people by 2026.
What should I do if I think I have yellow fever?▾▴
Seek urgent medical care if you develop fever within 14 days of travel to an endemic region. Tell the clinician about your travel history immediately. Avoid aspirin and other NSAIDs. Do not delay care if you experience jaundice, vomiting, reduced urine output, or any bleeding — toxic-phase disease requires intensive care.
Can I travel to areas with yellow fever?▾▴
Yes, with appropriate vaccination at least 10 days before travel. Carry the International Certificate of Vaccination or Prophylaxis (yellow card). Use insect repellent, sleep in screened or air-conditioned rooms, and avoid daytime mosquito bites. Consult a travel medicine clinic 4-6 weeks before departure.
Is yellow fever vaccine safe in HIV?▾▴
Yellow fever vaccine can be given to HIV-positive individuals with CD4 counts above 200 cells/µL and well-controlled HIV. Vaccine response may be weaker than in HIV-negative people, so booster doses are sometimes recommended. Severe immunosuppression (CD4 below 200 or active AIDS-defining illness) is a contraindication.
Apparent improvement on day 3-4 with defervescence and reduced symptoms — the brief remission.
06Return of fever, vomiting (sometimes with frank hematemesis — historic 'vomito negro' or 'black vomit'), and jaundice 24-48 hours after remission, marking the period of intoxication.
07Worsening jaundice and right-upper-quadrant abdominal pain from acute hepatic injury.
08Reduced urine output, dark or smoky urine, and rising creatinine from acute kidney injury.
•Profound hypotension with cold extremities — hemorrhagic or septic shock
•Severe hypoglycemia, lactic acidosis, or rapidly rising INR in the toxic phase
Plaque-reduction neutralization test (PRNT)
Confirms yellow fever-specific antibody and excludes cross-reaction with other flaviviruses
04
Liver function and coagulation panelGrades severity of hepatic injury and identifies impending hepatic failure
05
Renal function and electrolytesDetects acute kidney injury, electrolyte derangement, and metabolic acidosis in the toxic phase
06
Liver biopsy or post-mortem histologyDemonstrates pathognomonic mid-zonal hepatocyte necrosis and Councilman bodies in fatal cases
Outlook
Outcome is determined primarily by whether the patient enters the toxic phase and by availability of intensive supportive care. Approximately 50% of infections are asymptomatic; among symptomatic patients, 85% recover after the period of infection alone. The 15% who progress to the toxic phase face 30-60% mortality — substantially worse in resource-limited settings without intensive care, blood-product support, and renal replacement therapy. Survivors of severe disease usually recover hepatic and renal function over weeks to months, although some retain residual liver-function abnormalities. There is no chronic carriage and no long-term viral persistence outside immune-privileged sites. Yellow fever vaccine produces lifelong protection in over 95% of recipients per WHO 2013 SAGE position, although a small minority of vaccinated travellers may benefit from boosters under specific circumstances (HIV infection, vaccination during pregnancy, post-hematopoietic stem-cell transplant). The 2017 WHO EYE strategy aims to vaccinate 1 billion people in 27 high-risk countries by 2026 through mass preventive campaigns, routine childhood immunization, and outbreak response.
Residence or travel in endemic regionsenvironmental
47 countries in tropical Africa (notably Nigeria, Democratic Republic of Congo, Ethiopia, Sudan, Angola) and 13 in Central and South America (Brazil, Bolivia, Peru, Colombia, Venezuela) are endemic. Risk extends across rural and increasingly some urban areas.
Lack of yellow fever vaccinationmodifiable
Unvaccinated residents and travellers face the highest risk. Vaccine provides lifelong protection in over 95%. Travel medicine clinics routinely vaccinate travellers to risk areas at least 10 days before travel.
Occupational forest exposuremodifiable
Forest workers, hunters, soldiers, miners, ecotourists, and researchers entering jungle areas face elevated sylvatic exposure to canopy mosquitoes.
Urban Aedes aegypti densityenvironmental
Densely populated cities with high Aedes aegypti density (Luanda, Kinshasa, parts of Brazilian cities) are at risk of urban epidemics if virus is reintroduced.
Age extremes (vaccine-associated adverse events)non-modifiable
Yellow fever vaccine carries a slightly elevated risk of viscerotropic disease (YEL-AVD) and neurotropic disease (YEL-AND) in adults over 60 (about 1 per 100,000-400,000), infants under 9 months, and immunocompromised individuals. These groups need careful pre-vaccination evaluation.
Severe immunosuppression (HIV with CD4 under 200, organ transplantation, certain biologics)non-modifiable
Live vaccines including YFV are contraindicated in severe immunosuppression because of risk of disseminated vaccine virus. Risk-benefit assessment required before vaccinating mildly immunocompromised travellers.
Oral rehydration solution or balanced electrolyte drinks during fever
•Bland, easily digestible foods (rice, toast, bananas) during nausea
•Adequate protein intake during convalescence to support hepatic recovery
•Iron- and folate-rich foods for survivors of severe disease with anemia
foods to avoid
•Alcohol during acute illness and recovery — direct hepatic injury
•Aspirin and other NSAIDs
•Raw or undercooked food and unsafe water during travel to endemic regions
•High-fat fried foods during nausea phase
Anaphylactic reactions to the egg-based vaccine — rare and managed by expert vaccination centres.
choosing the right hospital
01Isolation room with mosquito-proof screening
02Critical-care capacity with renal replacement therapy
03Blood bank capable of supporting massive transfusion
03Avoid alcohol and unnecessary hepatotoxic medications during recovery.
04Use mosquito repellent and bed nets in endemic regions during convalescence and re-exposure prevention.
05Attend follow-up liver, kidney, and ophthalmology assessment as advised.
06Document yellow fever vaccination and infection history for future travel medicine consultations.
Exercise
Bed rest during acute febrile illness. Gradual return to physical activity during convalescence over 2-6 weeks; severe disease with hepatic involvement may take 8-12 weeks for full recovery. Avoid contact sports until coagulopathy and thrombocytopenia resolve.