Yellow Fever

infant bonobo, now thought to be Man's closest cousin, genetically.  The bonobo is a critically endangered species, with only 10,000 left surviving in isolated patches of forest in the Democratic Republic of Congo.  Like all primates, bonobos are at risk of catching Yellow Fever.  For their protection (as well as yours), it is imperative that all visitors are vaccinated.

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 (formerly known as Aedes) species.

The natural reservoir is monkeys and other primates in the forests of West 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'.

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'.

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 have also been a number of (mainly urban) outbreaks in Central Africa 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.


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.

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?


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 'short consultation' 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. What the visa/public health requirements are of the countries you plan to visit (i.e. do you need it to protect the local population?)
  3. Is it safe to give you the vaccination, considering your past/current medical history?
  4. Would another plan be more appropriate - e.g. delaying travel, Yellow Fever exemption certificate etc?

Nicky Armstrong and Jim Bond  March 2010

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