Yellow fever is a serious viral disease that is usually transmitted by a type of mosquito known as the Aedes aegypti mosquito. Yellow fever mainly occurs in sub-Saharan Africa (countries to the south of the Sahara desert), South America and in parts of the Caribbean. There have not been any recent cases of yellow fever in North America, Europe or Asia. Yellow fever can be fatal. About 5% of people who get yellow fever die from the condition.
Yellow fever was once one of the most feared epidemic diseases in the world with the capacity to bring devastation to almost every continent. Mass vaccination campaigns in the mid 20th Century succeeded in bringing the disease under control for over 40 years but since the late 1980s, this deadly disease has returned, putting at risk a new generation in West and Central Africa and threatening to erupt into devastating urban epidemics i.e., research or public health.