Germ theory of disease
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The germ theory of disease, also called the pathogenic theory of disease, is a scientific theory that suggests that instead of genetics being the proximal cause of many diseases that the environment plays a significant factor in the form of a pathogen microorganism such as bacteria or virus.
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Historical view of disease
The historical view is that disease was spontaneously generated instead of being created by microorganisms which grow by reproduction. One of the earliest references to this theory appears in On Agriculture by Marcus Terentius Varro (published in 36 BCE) wherein there is a warning about locating a homestead in the proximity of swamps which reads "...and because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases." (Varro On Agriculture 1,xii Loeb)
Microorganisms were first observed by Anton van Leeuwenhoek.
Louis Pasteur demonstrated that fermentation and the growth of microorganisms in nutrient broths was not caused by spontaneous generation. He exposed freshly boiled broths to air in vessels that contained a filter to stop all particles passing through to the growth medium: and even with no filter at all, with air being admitted via a long tortuous tube that would not pass dust particles. Nothing grew in the broths, therefore the living organisms that grew in such broths came from outside, as spores on dust, rather than being generated within the broth.
John Snow believed that the germ theory explained outbreaks of cholera, in opposition to the prevailing miasma theory of cholera.
List of pathogenic theories
- Peptic ulcers / highly suspected pathogenic cause: Helicobacter pylori
- Cervical cancer / highly suspected pathogenic cause: Human papilloma virus
- Schizophrenia / unknown, see pathogenic theory of schizophrenia
Need to mention:
- Ignaz Semmelweis
- vaccination
- Rossignol's challenge to Pasteur