Try doing a Google search of French medicine 1793. There is a little information in the Wikipedia article and more in an article on the Yellow Fever in Philadelphia. American doctors were not used to dealing with tropical fevers at this time. The French had colonies in tropical countries and had experienced first hand the disease and its treatment. Also try Googling the name of the Frenchman Doctor Deveze mentioned in the book. He was a real person who helped handle the outbreak of the disease in Philadelphia in 1793. His emphasis on cleanliness and using natural cures lead to a break through, not only saving the heroine in Fever 1793, but many others in real life.