Yellow fever : a current threat
- Geographical distribution
- Yellow fever resurgence : impact of mass vaccination campaigns
- Increased risk of urban yellow fever outbreaks in Africa
- Risk of international spread
The vast majority of cases and deaths take place in sub-Saharan Africa, where yellow fever is a major public health problem occurring in epidemic patterns. Africa also experiences periodic yet unpredictable outbreaks of urban yellow fever. Thirty-two African countries are now considered at risk of yellow fever, with a total population of 610 million people, among which more than 219 million live in urban settings.
Yellow fever is endemic in ten South and Central American countries and in several Caribbean islands. Bolivia, Brazil, Colombia, Ecuador, and Peru and Venezuela are considered at greatest risk. Although the disease usually causes only sporadic cases and small outbreaks, nearly all major urban centres in the American tropics have been reinfested with Aedes aegypti and most urban dwellers are vulnerable because of low immunization coverage. Latin America is now at greater risk of urban epidemics than at any time in the past 50 years.
The density and habitats of Aedes aegypti have expanded both in urban and rural areas. This mosquito is once again infesting regions from which it was previously eradicated. The disease was originally imported into the Americas from Africa, but became widely established there. Yellow fever has never been reported from Asia, but, should it be accidentally imported, the potential for outbreaks exists because the appropriate mosquito vector is present.
The boundaries and names shown and the designations used on these maps do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement.