Germ theory
Disease is caused by tiny living things — so wash your hands
See it on the timeline →In depth
Semmelweis showed as early as 1847 that handwashing cut puerperal fever dramatically, but was dismissed because he had no mechanism. Pasteur supplied the mechanism, Lister applied it in surgery, and Koch gave a method for linking a specific microbe to a specific disease. Combined with sewers, clean drinking water and later vaccines, this produced the largest rise in life expectancy in human history — from around 40 to over 70 years within a century.
For children
Doctors did not know why people got sick and often blamed "bad air". Pasteur and Koch showed that tiny bacteria are the cause. Once doctors began washing their hands and boiling instruments, people stopped dying from simple operations.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org