Germ theory of disease
From Freepedia
The germ theory of disease, also called the pathogenic theory of disease, is a theory that proposes that microorganisms are the cause of many diseases. Although highly controversial when introduced, it is now a cornerstone of modern medicine, leading to such important innovations as handwashing and antibiotics.
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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.
Fitness cost & the hard environmental view
Some scientists advocate the idea that the cause of any condition or behaviour that results in a significantly high fitness cost, which could be as low as 1% to 10%, is extremely unlikely to be genetic and thus is environmental. For example, if a gene had a fitness cost of 100% (so there could be no chance of offspring) then that gene would die out within one generation.
List of pathogenic / microorganism 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
- Homosexuality / speculative, see pathogenic theory of homosexuality
Need to mention:
- Ignaz Semmelweis
- vaccination
- Rossignol's challenge to Pasteur
