Yellow fever is very much still around. The virus actively circulates in 29 African countries and 13 countries across Central and South America, causing an estimated 200,000 infections and 30,000 deaths each year. As recently as late 2024, Colombia declared a significant outbreak that continued into 2025, with a high number of human deaths in a region where vaccination coverage sat at just 64%.
Where Yellow Fever Exists Today
Yellow fever is endemic across a wide band of tropical Africa and in forested regions of South America. In Africa, the list includes Nigeria, Democratic Republic of the Congo, Ethiopia, Kenya, Uganda, Ghana, Cameroon, and about 20 other nations stretching from Senegal in the west to Ethiopia in the east. In the Americas, Brazil, Colombia, Peru, Bolivia, Ecuador, Venezuela, Guyana, Suriname, French Guiana, Paraguay, Argentina, Panama, and Trinidad and Tobago all have areas where the virus circulates. In many of these countries, risk exists only in certain regions rather than nationwide.
The disease has never established itself in Asia, though the mosquito species capable of spreading it live there. Public health officials consider this a persistent concern, because a single infected traveler could theoretically spark transmission in a region with no population immunity.
Why It Can’t Be Eradicated
Yellow fever persists because of something called the jungle cycle. The virus doesn’t rely solely on humans to survive. It circulates continuously between mosquitoes and monkeys in tropical forest canopies across Africa and South America. When a person enters the forest for work or travel, an infected mosquito can pass the virus to them. That person can then carry it back to a town or city, where a different species of mosquito picks it up and spreads it person to person.
This three-layer transmission pattern (jungle, savannah, and urban) makes yellow fever fundamentally different from a disease like smallpox, which only lived in humans and could be eliminated through vaccination alone. As long as monkeys and forest mosquitoes maintain the virus in the wild, yellow fever will keep finding its way into human populations. Eradication is not a realistic goal. The best strategy is preventing epidemics through vaccination and rapid outbreak response.
Recent Outbreaks
The most notable recent event is the outbreak in Colombia’s Magdalena Valley that began in October 2024 and continued into 2025, involving deaths in both humans and monkey populations. The pattern closely mirrors what happened in Brazil between 2016 and 2018, when the virus surged through areas that weren’t previously considered high-risk, killing more people and primates than any outbreak in that country since 1980. Both outbreaks primarily struck unvaccinated people.
Colombia reported 216 confirmed cases between 2000 and 2023, spread across more than a dozen departments. A particularly deadly outbreak in the Catatumbo region during 2003 and 2004 had a mortality rate between 36% and 44%. These numbers illustrate that yellow fever isn’t a relic of the past. It continues to kill, especially where vaccination gaps exist.
What Happens When Someone Gets Infected
Most people who contract yellow fever either have no symptoms or experience a mild illness with fever, muscle aches, and nausea that resolves on its own. About 1 in 7 people with initial symptoms enter a dangerous second phase after a brief period of feeling better (sometimes just hours). This toxic phase brings high fever, jaundice (the yellowing of the skin and eyes that gives the disease its name), bleeding from the mouth, nose, eyes, and stomach, and organ failure. Between 30% and 60% of people who reach this stage die, typically within 7 to 10 days.
There is no antiviral treatment for yellow fever. Care is entirely supportive, focused on managing dehydration, fever, and organ function. This makes prevention through vaccination critically important.
The Vaccine Works, and One Dose Lasts a Lifetime
The yellow fever vaccine is one of the most effective vaccines ever developed. A single dose provides lifelong protection, and the World Health Organization officially amended international health regulations to reflect this, eliminating the need for booster shots. This makes the challenge largely one of access and delivery rather than science.
The WHO, UNICEF, and Gavi (the Vaccine Alliance) are midway through a 10-year strategy called EYE (Eliminate Yellow Fever Epidemics), which runs through 2026. The goal isn’t to eliminate the virus itself, since that’s impossible with the jungle cycle, but to end large-scale epidemics. The strategy centers on vaccinating every person in at-risk countries, maintaining a global emergency stockpile of 6 million vaccine doses at all times, and building the capacity to contain outbreaks quickly when they appear.
What This Means for Travelers
If you’re traveling to a country where yellow fever circulates, vaccination is not just recommended but often legally required. Some countries demand proof of vaccination from all arriving travelers. Others require it only if you’re coming from a country with yellow fever risk, even if you just had a brief layover there. You’ll need an International Certificate of Vaccination or Prophylaxis (sometimes called a “yellow card”) as documentation.
Travelers who can’t produce this certificate at the border may be denied entry, placed in quarantine, or vaccinated on the spot. If your trip involves rural or forested areas in endemic regions, the stakes go beyond paperwork. The jungle cycle means any time spent near forest areas in tropical Africa or South America carries real exposure risk, and the vaccine is your primary safeguard.
Diagnosis Is Harder Than You’d Think
One complication in tracking yellow fever is that it’s difficult to distinguish from other mosquito-borne infections, particularly dengue and Zika. The blood tests used to detect antibodies for these viruses cross-react with one another, meaning a yellow fever infection (or even a past yellow fever vaccination) can produce a false positive on a dengue test, and vice versa. In countries where these diseases overlap geographically, this makes accurate case counts challenging and likely means yellow fever is underreported in many regions.