Epidemics in the eighteenth century were regarded with apprehension and terror, understandable because there was little knowledge of their causes or treatment. In 1793, Philadelphia, the largest city in the nation, was in the grip of a yellow fever epidemic. The summer had been hot and dry, and there had been an influx of refugees from a revolution in the French colony of Sant Domingue (now Haiti), many of whom were already infected. Mosquitoes, which bred in stagnant pools of water, spread the disease. Christina Young Leech of Kingsessing, Pennsylvania, noted in her diary the effect of the epidemic on her family and on the city.
September 9th. My eldest son, William Leech, died at 7 o’clock in the morning of yellow fever, at the age of 37 years and two months, after a sickness of five days. Many people in the town died of this disease. …
There died in the town of Philadelphia, between the 1st of August, and November 9, 4031 people of yellow fever or pestilential fever; it bears a great resemblance to that dreadful disease, the plague. 17,000 inhabitants moved out of the City, and at Bush Hill was the Hospital; over 300 children lost father and mother, and were placed in one house to be cared for.
Modern scholars reckon the loss of life was closer to 5,000 people, a tenth of the city’s population of 50,000. The noted physician Dr. Benjamin Rush treated those stricken by bleeding and purges (induced vomiting and diarrhea), attempts to flush the disease out of the body. It was not discovered that yellow fever was spread by infected mosquitoes until 1881.