Germ Theory of Disease: How Pasteur and Koch Changed Medicine
In short: Louis Pasteur and Robert Koch proved that specific microbes cause specific diseases, replacing miasma theory and opening the way to vaccines, antiseptic surgery and laboratory diagnosis.
Pasteur's contributions
Louis Pasteur showed that microorganisms cause fermentation and spoilage, developed pasteurisation, and created vaccines against anthrax (1881) and rabies (1885). His work convinced scientists that germs, not bad air, cause many illnesses.
Koch's postulates
Robert Koch identified the anthrax bacillus (1876), the tuberculosis bacterium (1882) and the cholera vibrio (1883). His criteria — Koch's postulates — set out how to prove that a microbe causes a disease. 24 March, the day he announced the TB discovery, is now World TB Day.
Antisepsis and hygiene
Joseph Lister applied germ theory to surgery with carbolic acid in the 1860s, while Ignaz Semmelweis had already shown that handwashing reduced deaths from childbed fever. Hand hygiene remains the single most effective infection-prevention measure in hospitals.
Key takeaways
- Germ theory replaced miasma theory in the late 1800s.
- World TB Day (24 March) honours Koch's 1882 discovery.
- Handwashing is a direct legacy of germ theory.
Common questions
What are Koch's postulates?
A set of criteria: the microbe must be found in every case, isolated and grown, cause disease when introduced into a healthy host, and be re-isolated from that host.
Who invented the rabies vaccine?
Louis Pasteur, first used in a human in 1885.
References
Educational content by PHC-Nepal. It does not replace advice from a qualified health professional.