Yellow Fever

February 2010

What is Yellow Fever?

Yellow fever is a disease caused by a virus that is transmitted by the bite of an infected mosquito.  It gets its name from the yellowing of the skin and eyes (jaundice) that occurs when the virus attacks the liver. Yellow fever is a vaccine-preventable illness.  

 

 

 

Symptoms

• Can take 3 to 6 days to appear.
  
• Usually include sudden onset of fever, headache, joint pain, loss of appetite, abdominal pain, vomiting and dehydration. Most patients recover after this stage.
  
• In severe cases, can lead to shock, internal bleeding, jaundice (yellowing of the skin and eyes) and organ failure. This occurs in about 15% of patients. The case fatality ratio for those who develop severe yellow fever disease is 15-50%.
  

Transmission

• Yellow fever is spread through the bite of infected mosquitoes — mainly Aedes aegypti but with other Aedes species in Africa and Haemagogus species in South America also playing a role in transmission.
  
• These mosquitoes are either domestic (i.e. they breed around houses), wild (they breed in the jungle), or semi-domestic types (they display a mixture of habits). Any region populated with these mosquitoes can potentially harbour the disease.
  
• Non-human primates (monkeys) can also be infected with the yellow fever virus; this allows for the virus to remain present in rural or jungle areas without human hosts.
  
• Yellow fever epidemics occur in urban areas when infected people carry the disease from rural or jungle areas into densely populated areas where there are mosquitoes capable of spreading the disease.

Where is Yellow Fever a Concern?

• Yellow fever is endemic (always present) in many tropical areas of South America and Africa.
  
  • In South America, the countries considered to have the greatest risk of contracting yellow fever include Bolivia, Brazil, Colombia, Ecuador and Peru. Several Caribbean islands are also at low risk for epidemics.
    
  • Countries at risk for yellow fever in Africa are typically situated on or around the equator.
    
  • Yellow fever is not endemic in Asia, however since both the mosquitoes and the non-human primates are present in different parts of Asia, there is potential for future epidemics.

A list of countries where yellow fever transmission occurs and a map of the areas where yellow fever transmission occurs are available from the World Health Organization.

Related Travel Health Notices

Yellow Fever in Brazil

Recommendations for Travellers

1. Get vaccinated
   
   1. It is recommended that you get vaccinated against yellow fever.
      
      • The vaccine is available in Canada at designated Yellow Fever Vaccination Centres.
        
      • The yellow fever vaccine is not routinely recommended for pregnant women or nursing mothers, babies under the age of nine months, individuals with depressed immune systems and people with allergies to eggs, chicken, or gelatin. In addition, primary vaccination is not routinely recommended for adults over the age of 60 and people with a history of thymus disease.
        
      • Many countries will not allow travellers to enter without proof of vaccination (International Certificate of Vaccination).
        
2. Protect yourself from mosquito bites. Mosquitoes that spread yellow fever usually bite during the day, particularly two to three hours after dawn and during the early evening:
   
   1. Cover up: Wear light-coloured, long-sleeved, tucked-in shirts, long pants, shoes (not sandals), and a hat
      
   2. Use insect repellent on exposed skin:
      
      • Of the insect repellents registered in Canada, those containing DEET are the most effective
        
      • Use as directed by the manufacturer
        
      • Do not apply to cuts, abrasions or irritated skin
        
      • Do not spray directly on the face
        
      • Wash hands after application, to avoid contact with lips and eyes
        
      • When using sunscreen: do not use insect repellent and sunscreen combination products
        
      • If application of sunscreen and repellent with DEET is required, apply the sunscreen first and let it soak into the skin for about 20 minutes, then apply repellent with DEET
        
      • After returning indoors, wash off repellent.
        
   3. Sleep under a bed net, preferably treated with insecticide:
      
      • Ensure the net is intact (no tears or large holes)
        
      • Tuck it under the mattress
        
      • Ensure it is not touching you (or you still may be bitten through the net)
        
   4. Consider your accommodations: Stay in a well-screened or completely enclosed air-conditioned room
      
   5. Apply a permethrin insecticide to tents and clothing and other travel gear for greater protection
      • Permethrin-treated clothing is effective for up to 2 weeks or 6 washings
        
      • Although permethrin is not available in Canada, travel health clinics can advise you on how to purchase permethrin and pre-treated gear before or during your trip
      • This could be considered for playpens, crib, or strollers to protect young children

More information on precautions to take to avoid mosquito bites while travelling…

Don't Forget …

1. Consult a doctor, nurse, or health care provider or visit a travel health clinic at least six weeks before you travel.
   
2. What to do if you get sick when you are travelling.
   
3. What to do if you get sick after you return to Canada
   
4. Know what vaccines you need and when to get them

Other Related Information

Public Health Agency of Canada (PHAC) – Vaccine-Preventable Diseases: Yellow Fever

CATMAT – Statement on Personal Protective Measures to Avoid Arthropod Bites

World Health Organization (WHO) – Fact Sheet: Yellow Fever

WHO – Map of the Areas Where Yellow Fever Transmission Occurs

WHO – International Health Regulations