Yellow Fever outbreaks in South America and Africa


Recent outbreaks of Yellow Fever are continuing in South America and Africa

Yellow Fever (YF) is a disease caused by infection with yellow fever virus. It is considered to be one of the most lethal viral diseases. It is transmitted to humans through the bite of infected Aedes and Haemogogus mosquitoes. YF occurs in tropical regions of Africa and in parts of South America. Endemic regions include countries (or areas within countries) where there is the potential for human infection because of the presence of the mosquito vector and of the YF virus in non-human primates. To date YF has not appeared in Asia or the Pacific region. 

The WHO estimates that there are approximately 200,000 cases of yellow fever, causing 30,000 deaths, worldwide each year, with 90% occurring in Africa. 

Although ongoing cases and outbreaks of YF are occurring in Africa and South America, the disease is preventable by vaccination and remains a very rare cause of illness in travellers to these areas. From 1970 through 2015, a total of 10 cases of yellow fever were reported in unvaccinated travellers from the United States and Europe who travelled to West Africa (5 cases) or South America (5 cases). Eight (80%) of these 10 travellers died. There has been only 1 documented case of yellow fever in a vaccinated traveller. This nonfatal case occurred in a traveller from Europe who visited several West African countries in 1988. 

YF vaccination has two aims:

  1. To prevent the international spread of the disease by protecting countries from the risk of importing or spreading the yellow fever virus.
  2. To protect individual travellers who may be exposed to yellow fever infection.

Countries that require proof of vaccination are those where the mosquito vector and potential non-human primate hosts of YF are present. Any importation of the virus into such countries by infected travellers could result in its propagation and establishment, leading to a permanent risk of infection for the human population.

A single dose of yellow fever vaccine is enough to confer protection for life against yellow fever and a booster dose of the vaccine is not needed. The vaccine provides effective immunity within 30 days for 99% of persons vaccinated. 

Immunisation against yellow fever is indicated for the following groups:

  • Those travelling to, passing through or living in an endemic area
  • Those travelling to any country that requires an International Certificate of Vaccination or Prophylaxis for entry
  • Those handling potentially infectious materials (e.g. laboratory personnel) 

People who are usually excluded from YF vaccination include:

  • babies under nine months of age
  • pregnant and breastfeeding women
  • people over the age of 60
  • people with weakened immune systems – such as those with HIV
  • people who are very allergic to any of the ingredients in the vaccine – including people with an egg allergy 

Travellers to affected areas are advised to ensure that they:

  • receive the yellow fever vaccine at least 10 days before travelling to an affected area and
  • take precautions against mosquito bites, day and night, including:
  • Use of anti-mosquito devices (insecticide-treated bed nets, spray, repellents) and wear long sleeves and trousers
  • Mosquito repellent based on a 30% DEET concentration is recommended. Before using repellents, pregnant women and children under the age of 12 years should consult a physician or pharmacist
  • For new-born children under three months, repellents are not recommended. Insecticide-treated bed nets and protective clothing should be used instead 

Further sources of useful information:

  • The Centers for Disease Control and Prevention (CDC), US provides maps of Yellow Fever affected areas
  • World Health Organization (WHO) country list of YF vaccination requirements and recommendations
  • WHO suite of information on yellow fever in Portuguese 

Country requirements for YF vaccination are subject to change at any time.