What was the deadliest disease in the 1700s?

Smallpox: The Deadly Scourge of the 18th Century

Long before modern medicine reshaped global public health, smallpox reigned as one of the most lethal and feared diseases on Earth. Throughout the 1700s, this highly contagious virus swept through cities and towns across the globe, leaving behind high death rates, permanent scarring, and widespread panic.

Colonial America was hit particularly hard, with urban centers suffering devastating losses. Boston became a major epicenter for the virus, enduring severe epidemics in 1721, 1752, 1764, and 1775. During these recurring outbreaks, business ground to a halt and whole families were wiped out. The terror was so intense that early attempts at variolation—an early method of immunization that involved exposing healthy people to material from smallpox sores—caused massive public debates and social unrest.

It was not until Edward Jenner introduced the cowpox-based vaccine in 1796 that humanity finally gained a reliable weapon against the disease. Until that breakthrough, smallpox remained an uncontrolled killer, defining an era marked by medical helplessness and catastrophic loss.