Geographical distribution

Yellow fever is an endemic condition in the tropical areas of 44 African and Latin American countries (1).

• around 900 million people are at risk in these countries
  • an estimated 508 million people live in 31 countries at risk in Africa while the rest of the population at risk are in 13 countries in Latin America, with Bolivia, Brazil, Colombia, Ecuador and Peru.
• there are an estimated 200 000 cases of yellow fever resulting in 30,000 deaths worldwide each year
• in countries free of yellow fever, small number of patients may be seen due to imported cases (2)
• no cases of yellow fever were reported by 29 EU and EEA/EFTA countries in 2008 (3)

For reasons which are, as yet, poorly understood yellow fever has not been reported in Asia, despite the fact that the conditions required for transmission are present there (e.g. - the vector, Aedes aegypti)

There are two reservoirs of infection:

• humans:
  • person-to-person infection occurs primarily in cities
  • the mosquito vector is Aedes spp.
• monkeys:
  • monkey-to-monkey spread is in the jungle
  • the vector for monkey-to-monkey spread is A. africanus in Africa and the Haemagogus species in South and Central America
  • the vector for monkey-to-human spread are A. aegypti in Africa and Haemaogogus in South and Central America

Reference:

• (1) Thomas RE et al.The safety of yellow fever vaccine 17D or 17DD in children, pregnant women, HIV+ individuals, and older persons: systematic review. Am J Trop Med Hyg. 2012;86(2):359-72.
• (2) World Health Organization (WHO) 2013. Fact sheet. Yellow fever
• (3) European Centre for Disease Prevention and Control (ECDC). Annual epidemiological report on communicable diseases in Europe 2010.