Yellow Fever Vaccination Information

Introduction

Yellow fever is found only in parts of Central and South America and Sub-saharan Africa (see Yellow Fever Risk Areas).

The cause is a virus that is spread through the bite of an infected Aedes aegypti mosquito which predominantly bites during daylight hours. It exists in three transmission cycles; Jungle, Urban and Intermediate yellow fever.

Transmission Cycles

Jungle yellow fever - is transmitted among non-human hosts (mainly monkeys) via forest mosquitoes. Humans can become infected when they enter the forest habitat and can become the source of urban yellow fever outbreaks.

Urban yellow fever - is spread to urban areas by mosquitoes, mainly Aedes aegypti, that have bitten monkeys or humans infected with yellow fever. Urban yellow fever can occur in areas populated by man that are in close proximity to forests where infected monkeys and the mosquito vector can be found.

Both jungle and urban cases occur in Africa (especially west Africa). Urban cases are rare in the Americas.

Intermediate yellow fever - occurs only in Africa in humid savannah regions where mosquitoes infected both monkeys and humans causing localised outbreaks.

The Illness

The incubation period is usually short, 3-6 days. Symptoms of the disease include sudden onset of fever, backache, generalised muscle pain, nausea and vomiting. Jaundice can also be seen early in the disease and this intensifies as the disease progresses. Infection with yellow fever results in lifelong protection in individuals who survive. Up to 60% of those infected with yellow fever will die from the disease.

Treatment

There is no specific treatment for yellow fever virus.

Vaccination

Yellow fever vaccination is carried out for two different purposes:

  • To prevent the international spread of the disease by protecting countries from the risk of importing or spreading the yellow fever virus. These are mandatory requirements established by the country. The countries that require proof of vaccination are those where the disease may or may not occur and where the mosquito vector and potential non-human primate hosts of yellow fever are present. Any importation of the virus by an infected traveller could result in its propagation and establishment, leading to a permanent risk of infection for the human population. Proof of vaccination is often required for travellers coming from countries with risk of yellow fever transmission (including, sometimes, for travellers transiting through such countries).
  • Some countries require proof of vaccination from all travellers (see List of Countries with Mandatory Yellow Fever Certificate Requirement).
  • To protect individual travellers who may be exposed to yellow fever infection. As yellow fever is frequently fatal for those who have not been vaccinated, vaccination is recommended for all travellers (with a few exceptions) visiting areas where there is a risk of yellow fever transmission. An individual risk assessment is indicated for all travellers.

    (Reproduced with permission from the World Health Organisation)

Recommendations for Travellers

Travellers should be advised to use personal protective measures when entering areas where yellow fever is present. This includes using insect repellents and wearing appropriate clothing.

A vaccine called Stamaril is available for travellers to protect against yellow fever visiting risk areas. In addition, certain countries have yellow fever certificate requirements. Please refer to individual country records for information and certificate requirements.