Yellow Fever in Africa: Cause, Symptoms, and Treatment

By: Foluke Akinwalere.  Health & Wellness Writer. Medical review and editorial support provided by the DLHA Team.

 

Composite pictures of the close-up of the face of a black man with yellow eyes, the infected mosquito that causes yellow fever (Aedes aegypti) and a 3D image of the yellow fever virus (Flavivrus).. Click on image to enlarge.

 

Highlights

• Yellow fever is a serious mosquito-borne viral disease caused by a Flavivirus and transmitted primarily by the Aedes aegypti mosquito, especially in urban areas.
• Symptoms range from mild to severe, starting with fever, muscle pain, and nausea, and progressing in some cases to jaundice, bleeding, organ failure, and death.
• Africa remains heavily affected, with 13 countries in West and Central Africa considered endemic, particularly during the rainy season.
• Diagnosis involves both a checkup by your doctor, and special lab tests (including ELISA and RT-PCR).  Access to these tests for reliable diagnosis is limited in many parts of Africa.
• There is no specific antiviral treatment, but supportive care, including hydration and symptom management, can significantly improve outcomes.
• Vaccination is the most effective preventive measure, with a single dose offering lifelong protection.  It’s recommended for residents and travelers in endemic areas.
• Prevention also relies on mosquito control (using nets, spraying, and removing stagnant water) and strong outbreak response systems, including mass vaccination and surveillance.

 

Introduction

Yellow fever remains one of the most serious mosquito-borne diseases that is caused by a special type of germ called a virus. It is believed to have originated in Africa and introduced to the Americas during the transatlantic slave trade era. [1]

While modern medicine has made strides in prevention, outbreaks still pose a significant public health threat, particularly in West and Central Africa. With symptoms ranging from mild fever to severe organ failure, yellow fever is not a disease to take lightly.

In this article, you will learn about what causes yellow fever, its transmission, symptoms, how it is treated, and the essential steps for its prevention and control, especially in African communities most at risk.

 

Cause of Yellow Fever

Fig.1 Yellow fever virus transmission cycles in Africa. Image from CDC. Click on image to enlarge.

 

Yellow fever is a vaccine-preventable disease that is capable of causing large outbreaks. It is caused by an arbovirus from the Flavivirus group (a group of viruses mainly spread by mosquitoes and ticks).

The virus is primarily transmitted (spread) to humans through the bites of infected mosquitoes, especially Aedes aegypti, along with other Aedes species [2] (see figure 1).  The term “yellow” in the name refers to the jaundice, or yellowing of the eyes and skin that can develop in some patients. [3]  

Mosquito species involved in yellow fever transmission live in different environments. Some breed around human dwellings (domestic), others in forests or jungle areas (wild), and some in both settings (semi-domestic), which increase the potential for human exposure.

Yellow fever is spread through three main ways as follows:

• Sylvatic (jungle) cycle: The virus circulates between mosquitoes and wild primates like monkeys, occasionally infecting humans who travel or work in the forest areas where the virus is circulating.

• Intermediate (savannah) cycle:  This is the common type of outbreak in Africa. [1] This occurs in rural or semi-urban areas where semi-domestic mosquitoes infect both monkeys and humans.

• Urban cycle: In densely populated areas, infected mosquitoes can transmit the virus rapidly from person to person, leading to major outbreaks.

The following factors contribute to the spread and persistence of yellow fever in Africa:

• Deforestation (rampant wood felling in the forest without tree replanting efforts)
• Climate change 
• Urban overcrowding
• Poor sanitation

 

Patterns of Occurrence of Yellow Fever in Africa

Understanding the epidemiology (or occurrence pattern) of yellow fever in Africa involves looking at where the disease occurs, what factors contribute to its spread, and the scale of its impact.

• Geographical Distribution

According to the World Health Organisation, as of 2023, yellow fever is endemic in 34 African countries and 13 countries in Central and South America, or in specific areas where the disease is endemic. [4] 

However, since the beginning of 2023, and as of February 25, 2024, only 13 countries in the WHO African Region have recorded probable and confirmed cases of yellow fever [2] (See Fig. 2). 

Fig,2: Yellow fever endemic WHO African countries with recorded probable and confirmed cases (2023-2024). Click on image to enlarge.

 

Preliminary data from 2023 show a case fatality (death) rate (CFT) of 11% (i.e. about 10 deaths of every 100 cases).  Although the overall regional risk has been assessed as moderate and the global risk remains low, ongoing active surveillance is essential.  This is due to the potential for further spread through travel and the widespread presence of mosquito vectors capable of transmitting the disease in neighboring areas. [2]

• Burden and Outbreaks

Fig. 3: Countries in Africa where yellow fever vaccination is recommended (Current as of Dec. 2024). Source: CDC. Clcik on image to enlarge.

 

During outbreaks, yellow fever remains a major public health challenge in Africa, with serious consequences. In 2013, the burden of yellow fever was 84,000-170,000 severe cases and 29,000-60,000 deaths. [4] 

Sub-Saharan Africa has consistently recorded the highest cases of yellow fever, along with the fastest decline in cases. This downward trend is largely linked to strengthened global public health efforts, particularly through vaccination and mosquito control. While yellow fever cannot be eradicated completely because it persists in non-human primates, vaccination including in endemic areas remains a powerful tool for eliminating the disease among humans [1] (See figure 3).

 

Risk Factors for Yellow Fever

Several factors increase the likelihood of yellow fever transmission and outbreaks. These include: 

• Unvaccinated individuals:  People who have not received the yellow fever vaccine are at high risk, especially in endemic areas.

• Living in or traveling to endemic areas: Both residents and travelers can contract the disease if they are not protected.

• Urbanisation:  Rapid urban growth in many African countries often leads to crowded living conditions, poor sanitation, and stagnant water, all of which attract and support mosquito populations.

• Inadequate mosquito control:  Poor waste disposal, open water containers, and lack of insecticide use allow mosquitoes to thrive, especially in urban slums and rural communities.

• Climate change:  Rising temperatures and erratic rainfall patterns influence the geographic spread and survival of mosquitoes, which expand yellow fever risk zones into previously unaffected areas.

• Activities in endemic areas:  Occupational or recreational activities in wild or forested areas (like harvesting, ecotourism) can also increase the risk of mosquito bites.

• Cross-border movement:  Increased travel and migration across borders can spread the virus from one region to another.

• Age and health condition:  Some individuals are excluded from vaccination due to age factor or health condition. [3] This makes them at higher risk of contracting the disease.
  • Infant under 9 months 
  • Individual aged 60 and older
  • Pregnant women - except during a yellow fever outbreak when the risk of infection is high
  • Individual with severe allergies to egg protein
  • People with weakened immune systems (like those with HIV/AIDS or other causes)

 

Symptoms of Yellow Fever

Yellow fever symptoms can range from mild to severe (see fig. 4). Common initial symptoms which usually resemble flu or malaria include:

• Fever
• Headache and backache
• Muscle pain (myalgia)
• Fatigue (feeling tired)
• Loss of appetite
• Nausea and vomiting
• Backache
• Chills

Fig. 4: Yellow fever symptoms illustrated. Credit. Click on image to enlarge.

 

In severe cases, which often indicate a more serious illness, symptoms include:

• Jaundice: Yellowing of the eyes and skin, hence the name “yellow” fever.
• Bleeding: From the mouth, nose, eyes, or stomach (may be present in vomit or stool)
• Dark urine: Due to kidney problems.
• Abdominal pain
• Organ failure: Including liver and kidney failure
• In about half of the cases with severe symptoms, death can occur within 7 to 10 days if untreated. [2]

Important considerations:

• Once contracted, the yellow fever virus incubates in the body for 3 to 6 days. Many people infected with yellow fever may not experience any symptoms at all, or they may have very mild symptoms that are easily mistaken for other illnesses. [2]
• The severity of symptoms can vary greatly.

 

Diagnosis of Yellow Fever

Early diagnosis of yellow fever can be challenging because symptoms can be mild or mimic other illnesses, and more severe cases can be confused with malaria, dengue, or hepatitis. Therefore, diagnosing yellow fever involves a combination of clinical observation and laboratory testing.

Clinical Evaluation

• Travel History:  To find out whether the person has recently visited or lived in a region where yellow fever is common.
• Symptoms Check: Healthcare providers assess for typical symptoms such as high fever, headaches, muscle pain, yellowing of the skin or eyes (jaundice), and any signs of bleeding.
• Physical Examination:  During the exam, doctors check for physical indicators like elevated temperature, and bleeding-related symptoms.

Laboratory Diagnosis

To confirm yellow fever, several laboratory methods are used:

Virus Detection

• PCR (Polymerase Chain Reaction) Testing:  This method identifies the virus’s genetic code it uses to reproduce and spread inside the body; that is the virus’s RNA (Ribonucleic Acid) in a blood sample. This is effective during the early stage of infection, typically within the first few days.
• Virus Isolation:  In highly specialised laboratories, the virus can be cultured using cell lines or laboratory animals, though this is not commonly done for routine diagnosis.

Antibody Detection

• Serological Tests: Tests such as ELISA (enzyme-linked immunosorbent assay) and PRNT (plaque reduction neutralisation tests) are used to detect antibodies the immune system produces against the virus. IgM antibodies often appear early in the course of the disease.
• Consider Vaccination History: Reviewing the individual’s vaccination history is important, as IgM antibodies may appear due to a previous infection or as a response to vaccination.

Other Tests

• Complete Blood Count:  A low white blood cell count is often seen in the early phase of yellow fever.
• Blood Clotting Tests: Problems with how the blood clots may also be detected.
• Liver Tests:  High levels of bilirubin and liver enzymes can signal liver damage.

Important considerations

• Cross-Reactivity: Blood test such as serological tests can sometimes give false-positive results because the body’s response to other similar viruses like dengue or Zika virus, can look the same. [5]
• Short Presence of Virus in Blood:  The virus stays in the blood for only a short time, so a negative PCR test doesn’t always mean the person doesn’t have yellow fever. [5]
• Diagnosis in Fatal Cases:  In people who die from the disease, yellow fever can be confirmed by testing liver tissue samples. Also, other investigations depend on what organ is involved.

 

Treatment of Yellow Fever

There is no specific antiviral treatment for yellow fever.  Care focuses on relieving symptoms and supporting the functions of vital organs such as liver and kidney.

Supportive treatment includes:

• Intravenous (IV) fluids to prevent dehydration
• Pain and fever relief (avoiding aspirin due to bleeding risk)
• Monitoring and managing liver or kidney complications
• Blood transfusion in cases of severe bleeding

Early hospitalisation and professional care significantly improve chances of survival in severe cases.

 

Prevention and Control of Yellow Fever

Yellow fever can be prevented mainly through vaccination, avoiding mosquito bites, and controlling mosquitoes in the environment.

Vaccination

Getting vaccinated is the best way to prevent yellow fever.  Outbreaks can be avoided if most people are vaccinated.  The vaccine is very effective, low cost, and just one dose can protect you for life. People who recover from yellow fever also have lifelong protection. [6]

• How It Works: One dose of the WHO-approved yellow fever vaccine gives you full protection for life against the disease.

• Who Should Get It: It is recommended for people living in or traveling to places where yellow fever is found.

• Safety Tips: The vaccine is generally safe, but mild side effects like headaches, muscle aches, and low-grade fevers may occur. [7] People over 60 years old, those with weak immune systems, or certain medical conditions should talk to a doctor before getting vaccinated.

Avoiding Mosquito Bites

Here are the most effective ways to avoid mosquito bites:

• Use Repellents:  Apply mosquito repellent on exposed skin (Click here for more  CDC prevention tips on mosquito bites)

• Wear Protective clothing: Long sleeves and pants.

• Treat clothing:  Spray clothes with permethrin for added protection.

• Sleep under nets:  Use bed nets treated with insecticide, especially where mosquitoes bite during sleep.

• Limit exposure: During peak mosquito activity, stay inside and choose accommodations with screen/air-conditioning.

Mosquito Control

Here are effective ways to control mosquitoes in your environment:

• Eliminate mosquito breeding sites: Empty containers and old tires with standing water, and other potential habitats where mosquitoes can breed.

• Use larvicides: These are chemical substances that can stop mosquito larvae from developing in water storage areas.

• Spray insecticides:  These are chemicals substances that are sprayed to kill and reduce adult mosquito populations, especially during outbreaks.

• Get the community involved:  Encourage local efforts like clearing gutters, and covering water containers to reduce breeding sites.

Travel Regulations

Fig.5: International Certificate of Vaccination or Prophylaxis. Source CDC. Click on image to enlarge.

 

To reduce the spread of yellow fever across regions and countries, the WHO recommends that anyone traveling to or from areas where yellow fever is common should be vaccinated before their trip.  In fact, some countries were given the right to require travellers to provide a certificate of yellow fever vaccination, in accordance with the International Health Regulations (IHR). [3] The certificate (International Certificate of Vaccination or Prophylaxis), see fig. 5, serves as one of the conditions for entry to help protect both the traveler and the destination country from potential outbreaks.

Outbreaks Response

Tackling yellow fever outbreaks in Africa requires a comprehensive strategy that includes preventions, disease monitoring, vaccination efforts, and educating the public.  These include:

• Coordination and Planning

Countries create national plans focused on prevention, early detection, and vaccination. The WHO supports these efforts, working closely with affected nations. A global plan called the Eliminate Yellow Fever Epidemics (EYE) strategy brings partners together to stop yellow fever outbreaks. [2]

• Surveillance and Early Detection

Strong surveillance helps detect cases early. These efforts involve investigating the causes of outbreaks and identifying groups with low immunity to guide focused vaccination campaigns. Some countries, such as Cameroon, the Central African Republic, and Guinea have made progress in improving these systems. [2]

• Vaccination

Vaccination is a key tool in stopping outbreaks. Emergency campaigns respond to active outbreaks, while preventive ones protect people in high-risk areas.  The EYE Strategy aims to vaccinate nearly 1 billion people by 2026. [4]

• Vector Control

To stop the spread, mosquito control is important by eliminating potential mosquito breeding sites.

• Risk Communication and Community Engagement

Raising awareness about yellow fever and promoting vaccination is vital.  Efforts focus on reaching vulnerable groups like nomads, refugees, and displaced people. [2]

• Case Management

Improving hospital care and training health workers helps save lives. Early treatment in medical centers greatly increases survival chances.

• Addressing Challenges

Outbreaks still happen, this shows the need for constant readiness.  Challenges include reaching remote areas, limited healthcare access, and vaccine shortages, which require careful planning and prioritisation.

 

What Can Africans Do?

You can protect yourself and your community from yellow fever by:

• Getting vaccinated and encouraging others to do so.
• Using mosquito repellents, nets, and wearing protective clothing.
• Eliminating mosquito breeding sites around your home.
• Seeking prompt medical care if symptoms arise.
• Supporting community awareness programmes on prevention.

Individual responsibility, combined with community and government action, is key to controlling yellow fever.

 

Wrap Up

Yellow fever remains a major public health threat in Africa, but it is also entirely preventable.

With a safe and effective vaccine, proven mosquito control strategies, and swift outbreak responses, the disease’s burden can be reduced.

Take action by staying informed, protecting yourself and others, and advocating for strong public health systems that can respond quickly and equitably to yellow fever.

 

References

1.   Wang X, Li B, He B, Yan X, Huang L, Li J, Lai R, Lai M, Xie H, Mo Q, Chen L. The Incidence and Trends of Yellow Fever from 1990 to 2021 in Major Endemic Regions: A Systematic Analysis Based on the 2021 Global Burden of Disease Study. Pathogens. 2025 Jun 16;14(6):594. doi: 10.3390/pathogens14060594. Available from: here

2.   World Health Organisation Disease Outbreak News; Yellow fever in African Region (AFRO). [Internet].  20 March 2024. [Accessed July 1, 2025]. Available from  here

3.   World Health Organisation, Yellow Fever. [Internet] Accessed July 1, 2025 Available from here

4.   World Health Organisation. Yellow Fever. [Internet].  31 May, 2023. Accessed July 3, 2025.  Available from here

5.   Centers for Disease Control and Prevention, CDC. Clinical Features and Diagnosis of Yellow Fever. [Internet]. May 15, 2024. Accessed July 6, 2025 Available from here

6.   World Health Organisation, Health Topic, Yellow Fever. [Internet]. Available from here

7.   Centers for Disease Control and Prevention, CDC. Yellow Fever Vaccine, [Internet]. May 15, 2024. Accessed July 9, 2025. Available from here

 

 

Related 

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Click and watch the video below to learn more visually about Yellow Fever

 

 

Published: July 24, 2025

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