Yellow fever – the full guide to the responsible traveller

So, what is yellow fever? What is the name of the virus that causes it?

Yellow fever is an infection that is transmitted by the bite of a mosquito, similarly to the Dengue fever, West Nile virus and Zika (and many other diseases, of course). The virus belongs to the family of flaviviruses (similarly to Dengue and West Nile) and mainly affects the liver.
Keep in mind that most people that get infected do not develop symptoms and some develop a short illness that includes fever, headaches and muscle pain.
But some people develop a severe illness, with high fever, jaundice (this is where the yellow part of the name comes from), bleeding, encephalitis (infection of the cerebellum) and rarely – death.
Fortunately, children are more protected and develop a sub-clinical disease more commonly than adults.

What is the incubation period for disease?

The incubation period (the duration of time from the mosquito bite to the onset of symptoms) is approximately 3-6 days.

How is yellow fever diagnosed?

With the use of serology testing for antibodies or a PCR test in the blood or tissue.

What is the treatment for yellow fever?

There is no specific treatment for yellow fever, the only treatment that can be offered is supportive (reduction of fever, fluids, electrolyte corrections, acid-base balances and more). Therefore, the best way to protect ourselves is to simply avoid catching the infection.

Where is yellow fever common around the world?

The infection is found mostly in the tropical areas in Africa and South America. The countries that carry a higher risk for infection include Ghana, Kenya, Uganda, Nigeria, Peru, Brazil, Columbia and more. The mosquitos in these countries often carry the virus, and so anyone travelling to these countries could be exposed to a bite and subsequently to the infection.
The maps for yellow fever vary depending on the different outbreaks, so it is very important to search for the countries where there is a risk of infection prior to making travel plans. You can find teliable, up to date information, including cities and regions that are at higher risk on the American CDC website and the WHO website.

So how can we avoid yellow fever?

By protecting ourselves against mosquito bites and by getting vaccinated.

How can you protect yourself against mosquito bites?

Mosquitos can transmit yellow fever during the day and night. Therefore:
# Use nets and stay in air-conditioned rooms
# Use anti-bite products. Take a good look at the concentration of the active ingredient in the product and make sure to use one with a higher concentration so that it is more efficacious.
# Wear long sleeved clothes and avoid spending time outdoors in the evenings.

Is there a vaccine against yellow fever?

Certainly.
Certain countries have stringent rules about yellow fever vaccines, some countries require proof of vaccination prior to entry (it is also referred to as “international vaccine certificate”).
This requirement is not just a means to protect you, but also to protect the locals – so as not to bring in the virus from a different country. Obviously, it is also to prevent an outbreak in areas that have not yet had yellow fever.
For example, if you are staying in Africa and planning to fly to Brazil, you may need to present a certificate before entering Brazil. This requirement also applies if you just had a brief stop in a country that poses a high risk.

So, when and where can we get vaccinated?

It depends on your destination and where you are travelling from. Practically speaking, we can classify the destinations/countries in the world according to five different categories:
Areas where the vaccine is required and recommended:
1. When the travel destination is known to be a country that is endemic to yellow fever
Areas where the vaccine is required:
2. When the destination country requires anyone traveling to it to present a valid confirmation of having received the vaccine
3. When the destination country requires a person travelling from an endemic country to present a valid confirmation of having received the vaccine
4. When the destination country requires a person who was in transit (for any duration of time) at the airport of an endemic country to present a valid confirmation of having received the vaccine.
5. When the destination country requires a person who was in transit for longer than 12 hours at the airport of an endemic country to present a valid confirmation of having received the vaccine.

There are further exceptions to the above categories. For example, India requires anyone who visited or was in transit through a country known to be at risk, within the previous 6 days, to present a valid confirmation of having received the vaccine.

Which countries will require a vaccine certificate?

There are countries, particularly in Africa and South America, that require the person entering to provide an international vaccine certificate against yellow fever. For most countries in Africa (Ghana, Camron, Congo, Ivory Coast, Uganda, Nigeria) this is required for anyone entering. In some countries in south America, such as Bolivia and French Guiana, the requirement is similar. Countries that consider themselves “contaminated” may also require a certificate of vaccine when visiting them after having been at a country considered to be at high risk – including a long transit time.

Note that the rules may change depending on current outbreaks, and therefore before making any travel plans make sure to visit the official websites to find out about updated requirements:
– The American CDC: allows you to find out what countries are at higher risk and whether a vaccine is required
– The World Health Organization (WHO): publishes updates lists of countries where a vaccine is required

Travel offices are usually also able to provide you with this information, particular to your travel plans.

What do I need to know about the yellow fever vaccine?

The yellow fever vaccine is a live attenuated vaccine that is administered as a single intramuscular dose.

How many doses of vaccine do I need to receive?

According to the international regulations, a single dose of the vaccine is sufficient for life. Nonetheless, there are situation where a second dose is required (at least 10 years after the first dose) including:
1. When a patient is first vaccinated when they are under the age of 2
2. When travelling to areas that are at higher risk including Western Africa and areas with active outbreaks
3. When a traveller received the previous dose while being an HIV carrier.

When is a person considered protected after having received the vaccine?

The confirmation of vaccination is valid starting 10 days after receiving the vaccine. Therefore, it is important to make sure you get vaccinated 10 days early.

Who cannot receive the yellow fever vaccine?

• Children under the age of 9 months. Note that infants between the age of 6-9 months are sometimes able to get the vaccine, under certain exceptional situations and after having consulted with a travel physician.
• Travellers who have issues with the thymus cells, including myasthenia.
• People who are allergic to eggs. Getting the vaccine in an allergy clinic can be considered.
• A person who has an acquired or congenital immune deficiency
• Women who are breastfeeding or pregnant
• People over the age of 60 who have never received the vaccine – the benefits and risks of receiving the vaccines should be weighed due to the higher risk of side effects in this age group

So, what happens if the destination country requires proof of vaccine but you are unable to receive the vaccine?

In these situations, where there is a contraindication to receiving the vaccine, but the person is travelling to one of the countries that requires proof of vaccine, you can:
1. Rethink your travel plans – when I turn 70, I am not going to want to travel to a country with high risk of disease if I am not protected
2. The person can attain a vaccine waiver by a physician at the travel clinic.

What are the side effects of the vaccine?

There are several mild side effects including pain local to the area of administration, fever and weakness.

But there are also less frequent side effects that can be more severe when it comes to this live attenuated vaccine, and these include the actual infection and encephalitis.
Since certain groups of people are at higher risk of these severe side effects (immune deficient, babies and elders over the age of 60), the vaccine is only administered to travellers who are healthy and belong to one of the age groups mentioned above.

What about children?

As mentioned above, children over the age of 9 moths can receive the vaccine (and in certain situations, infants above the age of 6 months can receive it), and they are considered protected just like adults are after having received the injection.
Therefore, if you are planning on travelling with your baby at a very young age, I recommend deferring the trip or choosing a different destination.
In addition, children are mostly sensitive to dehydration and high fever, symptoms which may present with the actual infection, and so it is important to protect them as much as possible, both through the vaccine and use of protective measures against mosquito bites.

In summary, what do I need to do before travelling?

1. Check the travel destination – is there a risk of yellow fever? Does the country require proof of vaccination?
2. Approach your healthcare provider or a travel clinic – confirm whether the vaccine is needed and when you can receive it.
3. Keep your international vaccine certificate safe – just like you would with your passport, as you will not be able to travel without it to some of these countries.

And just as important – even if you have received the vaccine, it is still important to protect yourself from mosquito bites, wear long-sleeved clothes and avoid spending time outside at times when these mosquitos are most active. Don’t let a small mosquito ruin your trip, or your life.