An American Plague: The True and Terrifying Story of the Yellow Fever Epidemic of 1793

The final chapter relocates the setting to New York in 1858 amidst another yellow fever outbreak. Murphy stresses that little more is known about the disease than when it struck Philadelphia in 1793, and the consensus remains that it is imported. One difference is that a quarantine hospital is set up, but a mob who blames the Irish patients for bringing in the sickness burns it down.

Yellow fever continues to spread throughout several American cities during the 1800s, including Philadelphia. It also strikes other countries. France’s ambitions to expand their New World empire under Napoleon are foiled in the early 1800s, when tens of thousands of French soldiers fighting a Haitian slave revolt succumb to yellow fever. The fever also appears in South America, Europe, Russia, and West Africa. It emerges with warmer weather and large populations of people.

Throughout the 19th century, there are very few new developments regarding the disease. In 1848, Dr. Josiah Nott, a doctor in Alabama, observes that when the swamps are drained to kill mosquitoes, the fever seems to die off as well. Nott’s theory do not catch on until 1880, when Dr. Carlos Finlay decides to test it. He lets mosquitoes who have bitten sick patients feed from healthy people and finds that 20 percent of the latter group fall ill. While his peers do not see enough of a correlation to take the theory seriously, other findings in the 1880s regarding the discovery of bacteria and viruses open the door to revisiting the ideas of Nott and Finlay.

In 1900, Dr. Jesse Lazear, a doctor who is part of the US Army’s Yellow Fever Commission, investigates yellow fever in Cuba following the Spanish-American War. Several thousand US soldiers died of the fever during the war, while only a few hundred died from fighting. Lazear’s attention to the mosquito is also fueled by the recent discovery that mosquitoes carry the deadly disease malaria, which bears many similarities to yellow fever. Although Lazear has a hard time getting solid test results, he becomes convinced that the mosquito is to blame after the near death of a test subject, as well as one of his colleagues, James Carroll, following bites from mosquitoes. Lazear dies of yellow fever before his report is finished, but Carroll sends it along to Walter Reed, the head doctor of the Army commission.

Reed initiates experiments, finding that healthy test subjects placed in a tent with infected mosquitoes became sick. Reed also pinpoints the cause to the female Aedes aegypti mosquito. Although his results are initially met with some skepticism, his findings are eventually validated by other scientists. It will not be known that the original source of the disease is monkeys from the rainforests of Africa and South America until 1929, and a vaccine is not discovered until 1937. However, Reed’s experiments provide enough information to begin taking precautions, such as putting netting around infected patients. They also treat water with oil that kills mosquito larvae.

Due to its large number of open water sources, Philadelphia in 1793 is a perfect breeding ground for infected mosquitoes, which had been carried aboard ships and transported to the city. After discoveries in the 1900s, attempts are made to control yellow fever, but there is still no effective way to eradicate it. In 1947, efforts from the Pan American Sanitary Bureau to rid the Western Hemisphere of Aedes aegypti result in the indiscriminate spraying of a pesticide known as dichloro-diphenyl-trichloroethane, or DDT. The pesticide receives criticism in the 1960s and is eventually banned in 1972. The pesticide campaign also failed, as the mosquitoes who survived DDT produced offspring who were resistant to the chemical compound.

The mosquito is now understood to be responsible for spreading several different diseases, including West Nile and dengue fever, in addition to malaria and yellow fever. In the present day, increased encroachment on rainforests exposes humans to monkeys and mosquitoes potentially carrying disease. International travel can bring the infection to the United States, which is unprepared for a major outbreak; vaccination supplies are insufficient to handle a mass epidemic and there is still no cure. Although much has been learned from the past about controlling the disease, it remains “a struggle with no real end” (139).