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Yellow fever: a tropical disease that’s often underestimated

Published on January 29, 2019 at 13:30

If you’re planning to travel to a country where yellow fever is present, it is important to get vaccinated before you go, not only to protect yourself against the disease, but also to avoid getting turned away at the border. Be aware that some countries can refuse entry to travellers who do not show proof of yellow fever vaccination.

A mosquito-borne virus

Yellow fever is present in 44 countries, primarily in sub-Saharan Africa (for example in Burkina Faso, Ivory Coast, Kenya, and Senegal) and South America (notably Argentina, Brazil, Peru, and Venezuela). 

Like many tropical diseases, yellow fever is caused by a virus (flavivirus) that is transmitted to humans by infected mosquitos, which are found mostly in rural areas, but also in some urban and suburban environments. 

In the jungle or forest, mosquitos must first have bitten a monkey carrying the virus to be able to transmit it to humans. In urban settings, transmission can occur from one infected human to another, which can lead to yellow fever epidemics. 

To check whether yellow fever is a problem in the country you plan to visit, consult the Government of Canada’s travel health website at


In many cases the infection causes no symptoms. However, it can cause flu-like symptoms: sudden fever, headache, muscle pain, nausea, or vomiting. The symptoms usually appear 3 to 6 days after being bitten. 

Approximately 15% of people who are infected develop very serious symptoms that include severe vomiting, jaundice (which causes yellowing of the skin, hence the name of the infection), internal bleeding, and organ failure, which can be fatal. These severe symptoms appear rapidly, usually within 48 hours of the mosquito bite, and require emergency care.


There is no specific treatment for yellow fever, because the antiviral medicines available are not effective against flavivirus infections. Less serious symptoms such as fever and nausea can be relieved with over-the-counter medication. Avoid taking aspirin and non-steroidal anti-inflammatory drugs like ibuprofen, as they increase the risk of bleeding.


The yellow fever vaccine can be given even to children as young as 9 months. For maximum efficacy, you should get the vaccine at least 10 days before the date you plan to arrive in the at-risk country. The single-dose vaccine provides long-term immunity. 

Depending on your travel destination, vaccination may be recommended or mandatory. Some countries require travellers to show proof of yellow fever vaccination before they are allowed to enter the country, even if their only possible contact with the disease was during an airport stopover. Be sure to inquire in advance so you don’t get turned away at the border. 

It is important to book an appointment at a travel health clinic at least two months before your departure date, as other vaccines may also be recommended and may require more than one dose. What’s more, the vaccines may not be immediately available, for example in the case of a shortage.

Protect yourself against mosquitos, even if you’ve been vaccinated

In countries with tropical climates, insects can also transmit a host of other diseases for which there is no vaccine, e.g., malaria, dengue fever, leishmaniasis, and Zika virus. So, it is crucial to protect yourself against insect bites:

  • Use an insect repellent containing DEET (20 to 30%) or icaridin (20%). 
  • Wear light-colored clothing that covers your arms and legs (to make it easier to spot mosquitos) and that has been ideally treated with permethrin.
  • Tuck shirts into pants and tuck pants into socks.
  • Wear closed shoes.
  • Sleep under a mosquito net, and check regularly to ensure it has no tears or holes.

Your pharmacy: your travel health destination

Your pharmacist can prescribe various medicines to treat or prevent some health problems associated with travel, including malaria, traveller’s diarrhea, or acute altitude sickness. Many pharmacies also offer vaccination services. 

If you plan to travel in a country where health infrastructures are minimal, it is important to take along a first aid kit tailored to your destination and needs. Ask your pharmacist for advice to make sure you’ve got all the essentials. It is also an excellent idea to take a first aid course before you leave. 

If you take prescription medicine, your pharmacist can prepare a list of all your medications and provide you with enough of each product to cover a few extra days in the event of unexpected delays. 

If you’re planning a trip that will take you off the beaten path, be sure to inquire in advance about any specific medical risks associated with your destination so you come home in great health and with lots of happy memories! 

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