Yellow fever the introduction of sugar plantations created the conditions for mosquito and viral reproduction, and subsequent outbreaks of yellow fever. Deforestation reduced populations of insectivorous birds and other creatures that fed on mosquitoes and their eggs. Although yellow fever is most prevalent in tropical-like climates, the northern United States were not exempted from the fever. The first outbreak in English-speaking North America occurred in New York City in 1668, and a serious one afflicted Philadelphia in 1793. English colonists in Philadelphia and the French in the Mississippi River Valley recorded major outbreaks in 1669, as well as those occurring later in
Yellow fever vaccine It should not be given to those with very poor immune function. Yellow fever vaccine came into use in 1938. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale price in the developing world is between US$4.30 and US$21.30 per dose as of 2014. In the United States it costs between US$50 and US$100. The vaccine is made from weakened yellow fever virus. Some countries require a yellow fever vaccination certificate before entry from a country where the disease is common. People most at risk