Yellow Fever
	Know before you go!
	Disease profile
	Transmission
	Geographic distribution
	Table 1: YF-endemic countries
	Symptoms
	Treatment
	Vaccine
	International Health Regulations
	Table 2: Countries requiring YF vaccination
	Table 3: Countries requiring YF vaccination in some cases
	Prevention & precautions
	Some things to think about

Yellow Fever

Updated: December 2000

Know before you go!

Infectious diseases not necessarily common in Canada can occur and may even be widespread in other countries. Standards of hygiene and medical care may differ from those at home. Before departure, you should learn about the health conditions in the country or countries you plan to visit, your own risk of disease and the steps you can take to prevent illness.

The risk is yours
Your risk of acquiring a disease depends on several factors. They include: your age, gender, immunization status and current state of health; your itinerary, duration and style of travel (e.g., first class, adventure) and anticipated travel activities (e.g., animal contact, exposure to fresh water, sexual contact); as well as the local disease situation.

Risk assessment consultation
The Public Health Agency of Canada strongly recommends that your travel plans include contacting a travel medicine clinic or physician 6 to 8 weeks before departure. Based on your individual risk assessment, a health care professional can determine your need for immunizations and/or preventive medication (prophylaxis) and advise you on precautions to avoid disease. We can help you locate a travel medicine clinic closest to your home.

Some facts from the experts
The information below has been developed and is updated in consultation with Public Health Agency of Canada's Committee to Advise on Tropical Medicine and Travel (CATMAT). The recommendations are intended as general advice about the prevention of measles for Canadians travelling internationally.

Transmission

Yellow fever is transmitted to humans by the bite of infected mosquitoes from a variety of species, principally the Aedes and Haemagogus species. These mosquitoes are day-time biters.

There is no specific treatment for yellow fever. The overall case-fatality rate may reach 20% to 40% in single outbreaks. Deaths from yellow fever have been reported among unvaccinated travellers.

Vaccine

The single-dose 'live' vaccine for yellow fever is safe, effective and recommended for individuals 9 months of age and older. The vaccine becomes protective after 10 days, and provides immunity to a vaccinated individual for 10 years or more. For individuals who are pregnant, immuno-suppressed or allergic to eggs, the yellow fever vaccination may not be recommended. In Canada, the vaccination is available only at designated Yellow Fever Centres.

Individuals who receive the yellow fever vaccine are provided with an International Certificate of Vaccination as proof that they have been vaccinated against yellow fever.

International Health Regulations

Under the World Health Organization's International Health Regulations, a yellow fever vaccination certificate (i.e., International Certificate of Vaccination) may be required during international travel at border crossings. Some countries require all arriving travellers to show proof of yellow fever vaccination, while other countries require some travellers arriving or in transit from countries where yellow fever occurs to show proof of vaccination.

In order for the International Certificate of Vaccination for yellow fever to be considered valid, it must indicate that the individual was vaccinated at least 10 days prior to the date of entry to the country that requires proof of vaccination. As mentioned above, it takes 10 days for the vaccine to become protective.

Countries requiring the International Certificate of Vaccination for yellow fever are listed in the tables below.

Vaccination
The Public Health Agency of Canada strongly recommends travellers obtain an individual risk assessment with a travel medicine physician to determine both their risk of exposure to yellow fever and their need for official proof of vaccination as determined by their travel itinerary.

Mosquito-control precautions
Taking the following personal precautions may reduce the risk of exposure to day-time biting mosquitoes:

• remain in well-screened or completely enclosed, air-conditioned areas;
• wear light-coloured clothing with full-length pant legs and sleeves; and
• use insect repellent on exposed skin.

The use of insect repellent on exposed skin is strongly recommended. Of the insect repellents registered in Canada, those containing 'N, N diethyl-m-toluamide' (DEET) are the most effective. Although the concentration of DEET varies from product to product, repellency rates are largely equivalent. In general, higher concentrations protect for longer periods of time, but there is little advantage in the duration of repellence with DEET concentrations greater than 50%, and there may be additional risk of toxicity with higher concentrations. New micro-encapsulated products containing 33% DEET are registered in Canada, and they should provide up to 8 hours of protection.

Children and DEET
In rare instances, application of insect repellents with DEET has been associated with seizures in young children (only 14 cases over 30 years of DEET use and billions of applications every year). The actual concentration of DEET varies among repellents and can be as high as 95%. However, repellents with DEET concentrations of 10% are very effective and should last 3 to 4 hours. Therefore, for children, DEET in a concentration of 10% or less should be applied sparingly to exposed surfaces only and washed off after children come indoors.

The likelihood of adverse reactions can be minimized by the following precautions:

• apply repellent sparingly and only to exposed skin;
• avoid applying high concentration products;
• avoid applying repellents to portions of children's hands that are likely to contact the eyes or mouth;
• never use repellents on wounds or irritated skin; and
• wash repellent-treated skin after children come indoors. If a reaction to insect repellent is suspected, wash treated skin and seek medical attention.

In Canada, DEET products are not recommended for use in children less than 2 years of age. For more information on insecticide use, go to: Safety Tips on Using Personal Insect Repellent.

For more information...

• Visit the World Health Organization  - information on yellow fever
• and online publication Yellow fever Written by: Dr. Jari Vainio and Dr Felicity Cutts, London School of Hygiene and Tropical Medicine
• District guidelines for yellow fever surveillance WHO
• For maps of yellow fever-endemic area, visit  Centers for Disease Control and Prevention, USA
• For general information about other immunizations recommended for travel outside of Canada, click here.
• For more Know before you go! information, click here.

• The Travel Immunization Record is a practical booklet that helps you keep track of routine and specialized immunizations. To find out how to order a Travel Immunization Record (cost: $3.50 plus tax, shipping & handling), contact the Health Resources Centre, Canadian Public Health Association by email at hrccds@cpha.ca or by phone at 613-725-3769.