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Yellow Fever

Yellow Fever
Yellow Fever Risks in Regions Affected

The regions affected by Yellow Fever are typically tropical destinations surrounding the equator. The vast majority of the approximately 200,000 cases contracted each year occur in countries in equitorial Africa. Some countries in South America also pose a high risk for Yellow Fever, such as Peru, Ecuador, Brazil, Bolivia, and Colombia.

For ease of visualization, you may consult these two maps from the World Health Organization (WHO) showing the countries, highlighted in red, where Yellow Fever vaccination is recommended:


Yellow Fever Risks based on Traveler Activities

In the countries affected, Yellow Fever risk is typically low for travelers staying in highly developed urban areas, although there are known urban transmission cycles in both Africa and South America.
In contrast, risks for travelers visiting rural, jungle, or savannah areas are higher, and those staying in these areas for extended periods face the greatest risk.

Yellow Fever Overview

What is Yellow Fever?

Yellow Fever is a serious and potentially fatal flavivirus disease, which is similar to the West Nile Virus and Dengue Fever. Once infected, the virus attacks the liver, causing a yellowing of the infected's skin, which gave this illness its name.

How do you get Yellow Fever?

The Yellow Fever Virus is transmitted by bites from infected mosquitos.

What are the symptoms of Yellow Fever?

There are various stages of Yellow Fever, but in the initial stages, patients display flu-like symptoms such as fever, aching, headache and nausea. In this initial stage, patients to do not exhibit jaundice, or the yellowing of the skin. Please see the Symptoms section below for further details.

What are the treatments for Yellow Fever?

There is no known treatment for Yellow Fever once an individual is infected.

How can you prevent getting infected with Yellow Fever?
Fortunately, Yellow Fever can be prevented by vaccine, so it is critically important that travelers receive the single dose of vaccine required to be immunized against Yellow Fever at their local travel health clinic at least 10 days before they travel.

Yellow Fever Symptoms

Note that the symptoms described here are for individuals who contract the virus without previously being immunized against it.
Approximately 15% - 50% of people infected with the Yellow Fever virus go on to develop an illness, with flu-like symptoms, about 3 - 6 days after infection.
Of those that are infected, 60% - 85% recover after 3 to 4 days without developing the more serious, full Yellow Fever symptoms.
Of those that develop full Yellow Fever symptoms, they may initially experience fever, headache, joint and back pain, nausea, and dizziness.
Most individuals successfully recover after this stage. Those that do not, about 20% - 50% of the remaining patients, may in a matter of days, experience more serious symptoms such as jaundice, vomiting, haemorrhaging, and multi-organ failure including renal and cardiovascular issues, leading to death.

Yellow Fever Vaccination

Yellow Fever vaccination can only be administered by PHAC-approved clinics, called Yellow Fever Vaccination Centre clinics. These clinics are authorized to issue an International Certificate of Vaccination, which you may show to authorities at your travel destination as proof of your immunization against Yellow Fever.

Following adminstration of a single dose of the Yellow Fever vaccine, immunity quickly develops after 10 days, and persists for more than 10 years. Since immunity requires 10 days to develop, you must get vaccinated against Yellow Fever at least 10 days before you travel.

Yellow Fever Proof of Vaccination

Yellow Fever is one of the few diseases for which travelers are required to show proof of vaccination as a requirement for entry into some countries.
This proof of vaccination is called the International Certificate of Vaccination, and is issued by a designated Yellow Fever Vaccination Centre upon completion of immunization.
Please consult the following PDF document below from the World Health Organization for destination-specific information about which countries require this Certificate of Vaccination for entry. If there is a "Yes" listed in the right-most column next to your travel destination, then you are required to show proof of vaccination before entry into that country.

Here is an explanation of the columns in the above document, assuming you are departing from Canada:

- "Countries with risk of Yellow Fever Transmission"
If you are traveling to these countries, it is important that you be immunized against Yellow Fever.
- "Countries requiring Yellow Fever vaccination for travellers arriving from countries with risk of Yellow Fever transmission"
Canada is not a country with risk of Yellow Fever transmission, so you may ignore this column, unless you are departing from a different country that does have a risk of Yellow Fever transmission.
- "Countries requiring Yellow Fever vaccination for travellers from all countries"
If you are traveling to a country with a "Yes" in this column, you are required to be immunized against Yellow Fever, and additionally, you must show your International Certificate of Vaccination upon entry.

Yellow Fever Prevention

The best way to prevent infection is to be vaccinated against Yellow Fever at least 10 days before you travel at an accredited Yellow Fever Vaccination Centre, which will immunize you from the disease.

Other methods of prevention include:

  • Staying in Urban Areas
  • Discouraging Mosquito Bites by:
    • Cover exposed skin with hats and shoes
    • Wear light-coloured clothing
    • Use mosquito repellent (preferably DEET-based) on exposed skin
    • Apply a permethrin-based insecticide to clothing and tents
    • Sleep under a bed net
    • Stay in a completely-enclosed air-conditioned room
    • Avoid being outside 2-3 hours after dawn and during the early evening