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Yellow Fever


Disease Overview

Yellow fever virus is a ribonucleic acid (RNA) virus of the genus Flavivirus and is transmitted to humans through the bite of infected Aedes or Haemagogus mosquitoes. Yellow fever is endemic and intermittently epidemic in sub-Saharan Africa and tropical South America.1,2

Symptoms

Symptoms can take 3–6 days to appear:3

  • Sudden onset of fever
  • Chills
  • Headache
  • Joint and muscle pain
  • Loss of appetite
  • Abdominal pain
  • Back pain
  • Nausea
  • Vomiting
  • Fatigue
  • Weakness
  • Dehydration

Most patients recover after the initial stage; however, severe cases can occur in about 15% of patients, leading to shock, internal bleeding, jaundice and organ failure. About half of these patients will die within 10–14 days.3

Risk Factors

The risk for acquiring yellow fever is low for most travellers, particularly those staying in highly developed major urban areas. A traveller's risk for acquiring yellow fever is determined by factors such as:2,3

  • Immunization status.
  • Use of personal protection measures against mosquito bites.
  • Location of travel, particularly to rural or jungle areas.
  • Staying for longer periods of time.
  • Activities while travelling, such as camping, hiking, cycling or fieldwork.
  • Local rate of virus transmission.

In Canada and Around the World

In Canada between 2012 and 2021, a total of 15 cases of yellow fever were reported.4

Globally, the World Health Organization (WHO) estimates that approximately 200,000 cases occur annually, with up to 30,000 deaths.2

A total of 203 confirmed and 252 probable cases, including 40 deaths, were reported from January 1, 2021, to December 7, 2022, in 13 countries in the WHO African Region.5

The number of confirmed human cases in endemic countries of the Americas between 1960 and 2022 was 9,397, with a total of 2,451 reported between 2016 and 2022.6

Countries with yellow fever outbreaks in Africa and the Americas5-9
Africa (2021–2025) Americas (2021–2025)

Cameroon

Central African Republic

Chad

Burkina Faso

The Republic of the Congo

Côte d'Ivoire

The Democratic Republic of the Congo

Gabon

Ghana

Ginea

Kenya

Niger

Nigeria

Sierra Leone

South Sudan

Togo

Uganda

Bolivia

Brazil

Colombia

Guyana

Peru

Venezuela

 

NACI Vaccine Recommendations

In Canada, yellow fever vaccines can only be provided by Yellow Fever Vaccination Centres designated by the Public Health Agency of Canada.2

One dose of yellow fever vaccine is recommended for immunocompetent individuals who are 9 months of age and older and who travel to countries with risk of yellow fever transmission.2

According to the National Advisory Committee on Immunization (NACI), the decision to immunize a traveller against yellow fever should take into account considerations including but not limited to:2

  • The traveller's itinerary and associated risk for exposure.
  • Requirements of the destination country, including stopovers and airport transit.

Vaccination may not fully protect all vaccine recipients, and is not used to reduce or treat consequences of a condition following onset of illness.

  1. Centers for Disease Control and Prevention. Transmission of yellow fever virus. January 15, 2019. https://www.cdc.gov/yellowfever/transmission/index.html
  2. National Advisory Committee on Immunization. Yellow fever vaccine: Canadian immunization guide. September 8, 2023. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-25-yellow-fever-vaccine.html
  3. Government of Canada. Yellow fever. December 23, 2022. https://www.canada.ca/en/public-health/services/diseases/yellow-fever.html
  4. Public Health Agency of Canada. Reported cases from 1924 to 2021 in Canada - Notifiable diseases on-line: Yellow fever. Accessed September 18, 2024. https://diseases.canada.ca/notifiable/charts?c=pl
  5. World Health Organization (January 3, 2023). Disease Outbreak News; Yellow fever in East, West, and Central Africa. https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON431
  6. Pan American Health Organization – World Health Organization. Yellow fever: Number of confirmed human cases and deaths in endemic countries of the Americas, since 1960. https://ais.paho.org/phip/viz/ed_yellowfever.asp. Accessed February 16, 2023.
  7. Pan American Health Organization. Public Health Risk Assessment related to yellow fever: implications for the Americas Region. Feb 14, 2025. Retrieved from https://www.paho.org/sites/default/files/2025-02/2025-feb-14-phe-risk-assessment-yellow-fever-final.pdf
  8. World Health Organization (2024). Yellow Fever - African Region (AFRO). Retrieved from  https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON510
  9. World Health Organization (2024). South Sudan IDSR Weekly Bulletin Week 13, 25-31 March 2024. retrieved from https://www.afro.who.int/sites/default/files/2025-02/South%20Sudan%20IDSR%20Weekly%20Bulletin%20Week%2013%20%2C%2025%20-31%20March%202024.pdf

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