Chapter 1, Problem 1CCS

In the late 18th century, Philadelphia was one of the larger and wealthier cities in the United States and served as the capital. That changed in 1793. The city had an unusually wet spring, which left behind stagnant pools that became breeding grounds for mosquitoes. At about the same time, refugees from the slave revolution in Haiti fled to Philadelphia, carrying the yellow fever virus. In late August 1793, a female Aedes aegypti mosquito bit an infected refugee and then bit a healthy Philadelphian. This began a yellow fever epidemic that killed 10% of the city’s population within three months and led another 30% to flee for their lives. Victims suffered from high fever, nausea, skin eruptions, black vomit, and jaundice.

The treatment for yellow fever in the 18th century was often worse than the disease: physicians administered potions to purge the victims' intestines and drained up to four-fifths of their patients’ blood in the mistaken belief the bloodletting would stem fever. These attempted remedies often left patients tired, weak, and unable to fight the virus. Without effective treatments, the epidemic stopped only when the first frost arrived.

1. 1. People who left the city seemed to have milder cases of yellow fever or avoided the infection altogether. Explain why.
2. 2. The story mentions that the coming of the first frost brought an end to the epidemic. Discuss the possible reasons why this would provide at least temporary relief from the epidemic.