Yellow Fever Disease

Yellow Fever vaccine is just one of the travel vaccinations we offer at the Travel Clinic.  Yellow Fever vaccine can only be administered by a registered Yellow Fever Vaccination Centre.

Yellow Fever is an extremely serious viral infection, which can be transmitted to humans in some parts of the world by day-biting mosquitoes, typically Stegomyia (also known as Aedes) species.

The natural reservoir is monkeys and other primates in Africa and South America.  Monkey-to-human transmission (via mosquitoes) leads to sporadic cases of Yellow Fever in people living in or visiting forested areas, for example national parks.  This is sometimes known as 'jungle Yellow Fever' and is the most common route of transmission in South America.

Infected people, leaving the bush to more populated areas can then also cause onward human-human transmission (again via mosquitoes) and more widespread, cyclical outbreaks from time to time - so called: 'urban Yellow Fever'.  This is the more common mode of transmission in Africa.

Since 2015, there has been an epidemic of jungle Yellow Fever in South America, with spread of both monkey and human disease to countries and areas not previously affected or not affected for many decades. There has also been a number of (mainly urban) outbreaks in Central Africa (Angola, DRC, Congo and Uganda) in the past two years. The maps and categories of at-risk areas for Yellow Fever transmission have therefore recently been redrawn to take into account the shifting epidemiology.

How serious Is Yellow Fever?

Although most infections go unnoticed, in others there is a sudden-onset high fever, headache, back and muscle ache, nausea and vomiting.

In 15% of cases, the fever progresses to a more serious phase with liver failure and jaundice (hence 'Yellow'), abdominal pain and haemorrhagic symptoms such as bleeding from eyes, nose, bladder and gut.  Half of these cases die within 10-14 days.


  • Fortunately, there is a very effective vaccine available. This is given both a) to prevent the international spread of disease by protecting countries from travellers who may be carrying the virus, and b) to protect the individual traveller who may be exposed to infection.
  • Avoid getting bitten! Use Insect repellents and cover up exposed skin in at-risk areas. Even if you are protected against Yellow Fever by the vaccination, you may still be at risk from dengue, chikungunya (both spread by the same mosquitoes) and other diseases borne by biting beasties, for which there are no vaccinations available yet.

Mandatory Yellow Fever vaccination

For some regions, a valid 'international certificate of vaccination or prophylaxis' (or an exemption certificate) is required by immigration control to enter the country.  The vaccination certificate only becomes valid ten days after receiving the vaccine, but is now valid for life.

For details of which countries require a certificate, please visit

Please note that just because a country does not require a certificate to enter the country, this does not mean that there is no risk of infection in that country!

Yellow Fever vaccination: is it safe?

  • No vaccination is 100% free of side-effects.
  • Very rarely, encephalitis or liver problems may occur.  The risks of these more serious side-effects are relatively higher in elderly travellers who have not had the vaccine before.


  • Contraindications include: pregnancy, immunodeficiency from medication or disease, severe egg allergy and previous hypersensitivity reaction to the Yellow Fever vaccine.
  • Yellow Fever vaccine is not recommended for children under 9 months of age, (but may, depending on risk, be prescribed as early as six months of age by a specialist.)
  • The risks of more serious side-effects are relatively greater in the elderly.

If, after assessment, the risks to health are considered to outweigh the benefits, an exemption certificate may be issued by a registered Yellow Fever Vaccination Centre, such as the TrExMed Travel Clinic.

Yellow Fever Consultation

Some travellers are surprised to hear that they still need a 'single item appointment' before receiving a Yellow Fever vaccination, even if they have been told they need to have it by their own GP.  This is because, as responsible practitioners, we have to assess:

  1. What your actual risks are of acquiring Yellow Fever infection on your particular itinerary (i.e. do you really need it, to protect your health?)
  2. Is it safe to give you the vaccination, considering your past/current medical history (i.e. would the potential benefits of the vaccination outweigh the potential risks?)
  3. Would another plan be more appropriate - e.g. delaying travel, or issuing a Yellow Fever exemption certificate?

© Jim Bond Jan 2018

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