Yellow fever in Asia. Since the 1980s, the number of cases of yellow fever has been increasing. This is believed to be due to fewer people being immune, more people living in cities, people moving frequently, and changing climate increasing the habitat for mosquitoes. The disease originated in Africa, from where it spread to South America through the slave trade in the 17th century. Since the 17th century, several major outbreaks of the disease have occurred in the Americas, Africa, and Europe. In the 18th and 19th centuries, yellow fever was seen as one of the most dangerous infectious diseases. In 1927
1793 Philadelphia yellow fever epidemic the personal letters, which are largely held by Quaker colleges in the area. While Powell did not write a scholarly history of the epidemic, his work reviewed its historical importance. Since the mid-twentieth century, scholars have studied aspects of the epidemic, first in papers. For example, Martin Pernick's "Politics, Parties, and Pestilence: Epidemic Yellow Fever in Philadelphia and the Rise of the First Party System," developed statistical evidence to show that Republican doctors generally used Rush's therapies and Federalist doctors used Kuhn's. Scholars celebrated the 200th anniversary of the epidemic with the publication of papers on various aspects of the