Germ theory of disease

germ theorygermsbacteriological revolutiongermgerm-contaminated watergerm theory of diseasesbacterial infectionbacterial theorybiological theory of infectious diseasesdiscovery of actual infectious agents
The germ theory of disease is the currently accepted scientific theory for many diseases.wikipedia
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Pathogen

pathogenspathogenicpathogenicity
It states that microorganisms known as pathogens or "germs" can lead to disease. "Germ" may refer to not just a bacterium but to any type of microorganism or even non-living pathogen that can cause disease, such as protists, fungi, viruses, prions, or viroids.
A pathogen may also be referred to as an infectious agent, or simply a germ.

Virus

virusesviralvirion
"Germ" may refer to not just a bacterium but to any type of microorganism or even non-living pathogen that can cause disease, such as protists, fungi, viruses, prions, or viroids.
At the time it was thought that all infectious agents could be retained by filters and grown on a nutrient medium—this was part of the germ theory of disease.

Microorganism

microorganismsmicrobemicrobes
It states that microorganisms known as pathogens or "germs" can lead to disease.
Thus, Pasteur refuted the theory of spontaneous generation and supported the germ theory of disease.

Louis Pasteur

PasteurPasteur, LouisPasteurian
A transitional period began in the late 1850s with the work of Louis Pasteur.
His medical discoveries provided direct support for the germ theory of disease and its application in clinical medicine.

Robert Koch

KochDr Robert KochKoch, Robert
This work was later extended by Robert Koch in the 1880s.
His work with anthrax is notable in that he was the first to link a specific microorganism with a specific disease, rejecting the idea of spontaneous generation and supporting the germ theory of disease.

Girolamo Fracastoro

FracastoroFracastoriusFracastoro’s Homocentrica
Basic forms of germ theory were proposed in the late Middle Ages by physicians including Ibn Sina in 1025, Ibn Khatima and Ibn al-Khatib in the 14th century, and Girolamo Fracastoro in 1546, and expanded upon by Marcus von Plenciz in 1762.
His theory remained influential for nearly three centuries, before being superseded by a fully developed germ theory.

Smallpox vaccine

smallpox vaccinationsmallpox inoculationvaccination
By the early nineteenth century, smallpox vaccination was commonplace in Europe, though doctors were unaware of how it worked or how to extend the principle to other diseases.
In the early empirical days of vaccination, before Pasteur's work on establishing the germ theory and Lister's on antisepsis and asepsis, there was considerable cross-infection.

Bacteriology

bacteriologistbacteriologicalbacteriologic
Eventually, a "golden era" of bacteriology ensued, during which the theory quickly led to the identification of the actual organisms that cause many diseases.
Bacteriology evolved from physicians needing to apply the germ theory to test the concerns relating to the spoilage of foods and wines in the 19th century.

Scientific theory

theoryscientific theoriestheories
The germ theory of disease is the currently accepted scientific theory for many diseases.

Ignaz Semmelweis

SemmelweisIgnaz Philipp SemmelweisIgnác Semmelweis
Ignaz Semmelweis, a Hungarian obstetrician working at the Vienna General Hospital (Allgemeines Krankenhaus) in 1847, noticed the dramatically high maternal mortality from puerperal fever following births assisted by doctors and medical students.
Semmelweis's practice earned widespread acceptance only years after his death, when Louis Pasteur confirmed the germ theory, and Joseph Lister, acting on the French microbiologist's research, practised and operated, using hygienic methods, with great success.

Bacteria

bacteriumbacterialEubacteria
"Germ" may refer to not just a bacterium but to any type of microorganism or even non-living pathogen that can cause disease, such as protists, fungi, viruses, prions, or viroids.
(Yeasts and moulds, commonly associated with fermentation, are not bacteria, but rather fungi.) Along with his contemporary Robert Koch, Pasteur was an early advocate of the germ theory of disease.

Agostino Bassi

Bassi
The Italian Agostino Bassi was the first person to prove that a disease was caused by a microorganism when he conducted a series of experiments between 1808 and 1813, demonstrating that a "vegetable parasite" caused a disease in silkworms known as calcinaccio which was devastating the French silk industry at the time.
He preceded Louis Pasteur in the discovery that microorganisms can be the cause of disease (the germ theory of disease).

Miasma theory

miasmamiasma theory of diseasemiasmas
However, such views were held in disdain in Europe, where Galen's miasma theory remained dominant among scientists and doctors. John Snow was a skeptic of the then-dominant miasma theory.
The theory was eventually given up by scientists and physicians after 1880, replaced by the germ theory of disease: specific germs, not miasma, caused specific diseases.

Nicolas Andry

AndryNicholas AndryNicolas Andry Award
In 1700, physician Nicolas Andry argued that microorganisms he called "worms" were responsible for smallpox and other diseases.
Andry's early medical work lies within the nascent germ theory of disease.

Microbiology

microbiologistmicrobiologicalbacteriology
Microorganisms are said to have been first directly observed in the 1670s by Anton van Leeuwenhoek, an early pioneer in microbiology, considered "the Father of Microbiology".
Koch is best known for his contributions to the germ theory of disease, proving that specific diseases were caused by specific pathogenic microorganisms.

Marcus von Plenciz

Basic forms of germ theory were proposed in the late Middle Ages by physicians including Ibn Sina in 1025, Ibn Khatima and Ibn al-Khatib in the 14th century, and Girolamo Fracastoro in 1546, and expanded upon by Marcus von Plenciz in 1762.
Marcus von Plenciz (1705-1786) was a Vienna physician credited with advancing the germ theory of disease.

Contemporary reaction to Ignaz Semmelweis

fellow doctors rejectedrejectedResponse to Semmelweis
Despite this evidence, he and his theories were rejected by most of the contemporary medical establishment.
His unpalatable observational evidence was only accepted when seemingly unrelated work by Louis Pasteur in Paris some two decades later offered a theoretical explanation for Semmelweis's observations: the germ theory of disease.

Soho

Soho, LondonBroad Street pumpSoho district
In 1855 he published a second edition of his article, documenting his more elaborate investigation of the effect of the water supply in the Soho, London epidemic of 1854.
This is an early example of epidemiology, public health medicine and the application of science—the germ theory of disease—in a real-life crisis.

Epidemiology

epidemiologistepidemiologicalepidemiologists
It is regarded as one of the founding events of the science of epidemiology.
The development of a sufficiently powerful microscope by Antonie van Leeuwenhoek in 1675 provided visual evidence of living particles consistent with a germ theory of disease.

John Snow

Dr John SnowDr. John SnowJohn Snow (physician)
John Snow was a skeptic of the then-dominant miasma theory.
The germ theory of disease had not yet been developed, so Snow did not understand the mechanism by which the disease was transmitted.

Germ theory denialism

denial of the germ theory of diseasedenieddo not believe
Germ theory denialism is the pseudoscientific belief that germs do not cause infectious disease, and that the germ theory of disease is wrong.

Boil-water advisory

boil water advisoryboil orderboil water notice
Snow's 1849 recommendation that water be "filtered and boiled before it is used" is one of the first practical applications of germ theory in the area of public health and is the antecedent to the modern boil-water advisory.
John Snow's 1849 recommendation that water be "filtered and boiled before it is used" is one of the first practical applications of the germ theory of disease in the area of public health and is the antecedent to the modern boil water advisory.

Joseph Lister

Joseph Lister, 1st Baron ListerListerLord Lister
In the 1870s, Joseph Lister was instrumental in developing practical applications of the germ theory of disease with respect to sanitation in medical settings and aseptic surgical techniques—partly through the use of carbolic acid (phenol) as an antiseptic.
A surgeon was not required to wash his hands before seeing a patient; in the absence of any theory of bacterial infection, such practices were not considered necessary.

Richard Bradley (botanist)

Richard Bradley
In 1720, Richard Bradley theorised that the plague and 'all pestilential distempers' were caused by 'poisonous insects', living creatures viewable only with the help of microscopes.
Though spread across a handful of his papers, when taken together, a unified, biological theory of infectious diseases spanning all life – from plants and animals to humans – emerges.

Dot distribution map

dot mapDot maps
Snow later used a dot map to illustrate the cluster of cholera cases around the pump.
The map helped the germ theory of disease transmission supplant miasma theory as the widely accepted view.