Yellow fever is a viral hemorrhagic disease transmitted primarily by mosquitoes. It poses a significant threat in tropical and subtropical regions, especially in parts of Africa and South America. This guide provides essential information about yellow fever, including its symptoms, transmission, prevention, and treatment.

What is Yellow Fever?

Yellow fever is caused by the yellow fever virus, a flavivirus, which is transmitted to humans through the bites of infected mosquitoes, particularly Aedes aegypti. The disease gets its name from the jaundice that affects some patients, causing their skin and eyes to turn yellow.

Yellow fever virus taken using an electron microscope

Yellow Fever Risk Countries

  1. Africa:
    Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Rep., Chad, Côte d'Ivoire, Dem. Rep. of the Congo, Equatorial Guinea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Mali, Mauritania, Niger, Nigeria, Republic of the Congo, Senegal, Sierra Leone, South Sudan, Sudan, Togo, Uganda

  2. South America:
    Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago (Trinidad only), Venezuela

Symptoms of Yellow Fever

Symptoms of yellow fever typically appear 3-6 days after infection. The illness has three phases:

  1. Initial Phase:

    • Fever
    • Chills
    • Severe Headache
    • Back Pain
    • General Body Aches
    • Nausea and Vomiting
    • Fatigue and Weakness

  2. Remission Phase:

    • Temporary Improvement whereby symptoms may subside for a few hours or days.

  3. Toxic Phase:

    • Return of Fever
    • Jaundice (yellowing of the skin and eyes)
    • Abdominal Pain
    • Vomiting, sometimes with blood
    • Bleeding from the mouth, nose, eyes, or stomach
    • Kidney and Liver Dysfunction
    • Shock and Organ Failure

Approximately 15% of patients enter the toxic phase, which can be fatal. However, 50% of those who progress to this phase die within 7-10 days.

Transmission of Yellow Fever

Yellow fever is transmitted primarily through the bites of infected Aedes mosquitoes, which are active during the daytime. The virus can also be transmitted through:

  • Jungle (Sylvatic) Cycle: Involves transmission between non-human primates (monkeys) and mosquitoes in tropical rainforests.
  • Urban Cycle: Involves transmission between humans and mosquitoes in densely populated areas.
  • Intermediate (Savannah) Cycle: Involves transmission between humans or monkeys and mosquitoes in semi-domestic areas of Africa.
    A female Aedes aegypti mosquito obtaining a blood meal from a human host.

Diagnosing Yellow Fever

Diagnosis of yellow fever is based on symptoms, recent travel history, and laboratory tests. Common diagnostic methods include:

  • Blood Tests: To detect the presence of yellow fever virus or antibodies.
  • Polymerase Chain Reaction (PCR): To detect viral RNA in blood samples.
  • Serology: To identify specific antibodies against the virus.

Preventing Yellow Fever

Prevention focuses on vaccination and mosquito control measures. Here are some effective strategies:

  1. Vaccination:

    • Yellow Fever Vaccine: A single dose of the yellow fever vaccine provides lifelong immunity and is recommended for people aged 9 months and older who are traveling to or living in areas at risk. Some countries require proof of vaccination for entry.
      Person being vacinated against Yellow Fever virus
  2. Avoid Mosquito Bites:

    • Use Insect Repellents: Apply repellents containing DEET, Picaridin, or IR3535 to exposed skin.
    • Wear Protective Clothing: Long sleeves, long pants, and socks provide a physical barrier against mosquito bites.
    • Use Mosquito Nets: Sleep under insecticide-treated mosquito nets (ITNs) to prevent bites while sleeping.
    • Stay Indoors During Peak Activity: Mosquitoes are most active at dawn and dusk. Stay indoors or take precautions during these times.
      Mosquito net installed on a bed to prevent insect bites at night
  3. Eliminate Mosquito Breeding Sites:

    • Remove Standing Water: Empty and clean containers that collect water, such as flower pots, buckets, and bird baths.
    • Maintain Clean Surroundings: Keep your environment clean to reduce mosquito breeding sites.
  4. Community Efforts:

    • Participate in Community Clean-Up Campaigns: To eliminate mosquito breeding sites.
    • Support Local Health Authorities: In their efforts to control mosquito populations.

Treating Yellow Fever

There is no specific antiviral treatment for yellow fever. Treatment focuses on relieving symptoms and supporting vital functions:

  • Hospitalization: Patients with severe symptoms or complications may require hospitalization.
  • Supportive Care: Includes intravenous (IV) fluids, oxygen therapy, and maintaining blood pressure.
  • Medications: Use pain relievers and fever reducers such as acetaminophen (paracetamol). Avoid aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, as they can increase the risk of bleeding.
  • Monitoring: Close monitoring for complications like liver and kidney failure.

Yellow Fever Conclusion

Yellow fever is a serious and potentially fatal disease that requires prompt medical attention. By understanding the symptoms, transmission, and preventive measures, you can protect yourself and your loved ones from yellow fever. Vaccination is the most effective way to prevent the disease, and taking precautions to avoid mosquito bites is crucial.

For more information on yellow fever prevention and treatment, consult your healthcare provider or visit reputable health websites such as the World Health Organization (WHO) and the Hospital for Tropical Diseases (HTD)