In the book Graveyard Girl, by Anne Meyers, 12-year-olds Eli and Addie struggle to survive during a yellow fever epidemic in 1878, but do thanks to the help of some unexpected visitors.

Yellow fever is a disease spread through the bite of a mosquito. Most outbreaks occur in Africa and South America. People with yellow fever experience symptoms similar to the flu including, headache, fever, vomiting, and aches and pains. If it progresses without the help of a doctor there may be hemorrhaging, jaundice, or yellowing of the skin, which is why it is called yellow fever. If yellow fever goes untreated about 10% of the patients die, but those who survive cannot ever get it again.

Information from:
Berenbaum, May R. Bugs in the System. Addison-Wesley Publishing Company, 1995