On Aug. 1, 1793, it was reported that a fever, now known as ‘Yellow Fever’ killed more than 5,000 people in Philadelphia between August and November.

Philadelphia, then the nation’s capital, was the most cosmopolitan city in the United States. The Fall frost killed the mosquitoes and ended the epidemic.

Yellow fever is a viral disease that is transmitted to humans by the bites of infected mosquitoes. It is prone to epidemics and today is preventable with a vaccine.