The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases. Although highly controversial when first proposed, it is now a cornerstone of modern medicine and clinical microbiology, leading to such important innovations as antibiotics and hygienic practices.^[1] The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... A disease is any abnormal condition of the body or mind that causes discomfort, dysfunction, or distress to the person affected or those in contact with the person. ... An agar plate streaked with microorganisms Microbiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. ... An antibiotic is a drug that kills or slows the growth of bacteria. ... Hygiene refers to practices associated with ensuring good health and cleanliness. ...

History

The ancient historical view was that disease was spontaneously generated instead of being created by microorganisms which grow by reproduction.^[1] The Atharvaveda is the first ancient text dealing with medicine. It identifies the causes of disease as living causative agents such as the yatudhānya, the kimīdi, the kṛimi and the durṇama. The atharvāns seek to kill them with a variety of drugs in order to counter the disease (see XIX.34.9). One of the earliest western references to this latter theory appears in On Agriculture by Marcus Terentius Varro (published in 36 BC) wherein there is a warning about locating a homestead in the proximity of swamps: Abiogenesis, in its most general sense, is the hypothetical generation of life from non-living matter. ... For other uses, see Reproduction (disambiguation) Reproduction is the biological process by which new individual organisms are produced. ... The Atharvaveda (Sanskrit: अथर्ववेद, , a tatpurusha compound of , a type of priest, and meaning knowledge) is a sacred text of Hinduism, and one of the four Vedas, often called the fourth Veda. According to tradition, the Atharvaveda was mainly composed by two groups of rishis known as the Bhrigus and the... Marcus Terentius Varro ([[116 BC]–27 BC), also known as Varro Reatinus to distinguish him from his contemporary Varro Atacinus, was a Roman scholar and writer, who the Romans came to call the most learned of all the Romans. ... Centuries: 2nd century BC - 1st century BC - 1st century Decades: 80s BC 70s BC 60s BC 50s BC 40s BC - 30s BC - 20s BC 10s BC 0s 10s 20s Years: 41 BC 40 BC 39 BC 38 BC 37 BC 36 BC 35 BC 34 BC 33 BC 32 BC...

In The Canon of Medicine (1020), Abū Alī ibn Sīnā (Avicenna) stated that bodily secretion is contaminated by foul foreign earthly bodies before being infected.^[3] He also discovered the contagious nature of tuberculosis and other infectious diseases, and introduced quarantine as a means of limiting the spread of contagious diseases.^[4] A Latin copy of the Canon of Medicine, dated 1484, located at the P.I. Nixon Medical Historical Library of The University of Texas Health Science Center at San Antonio. ... (c. ... Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. ... Tuberculosis (abbreviated as TB for tubercle bacillus or Tuberculosis) is a common and deadly infectious disease caused by mycobacteria, mainly Mycobacterium tuberculosis. ... This false-colored electron micrograph shows a malaria sporozoite migrating through the midgut epithelia. ... This article does not cite any references or sources. ...

When the Black Death bubonic plague reached al-Andalus in the 14th century, Ibn Khatima discovered that infecious diseases are caused by microorganisms which enter the human body. Another 14th century Andalusian physician, Ibn al-Khatib, wrote a treatise called On the Plague, in which he stated:^[3] This article concerns the mid fourteenth century pandemic. ... The bubonic plague or bubonic fever is the best-known variant of the deadly infectious disease caused by the enterobacteria Yersinia pestis. ... Al-Andalus is the Arabic name given the Iberian Peninsula by its Muslim conquerors; it refers to both the Caliphate proper and the general period of Muslim rule (711–1492). ... A cluster of Escherichia coli bacteria magnified 10,000 times. ...

"The existence of contagion is established by experience, investigation, the evidence of the senses and trustworthy reports. These facts constitute a sound argument. The fact of infection becomes clear to the investigator who notices how he who establishes contact with the aftlicted gets the disease, whereas he who is not in contact remains safe, and how transmission is affected through garments, vessels and earrings."

Girolamo Fracastoro proposed in 1546 that epidemic diseases are caused by transferable seedlike entities that could transmit infection by direct or indirect contact or even without contact over long distances. Girolamo Fracastoro (Fracastorius) (1478‑1553) was an Italian physician, scholar and poet. ... // Events Spanish conquest of Yucatan Peace between England and France Foundation of Trinity College, Cambridge by Henry VIII of England Katharina von Bora flees to Magdeburg Science Architecture Michelangelo Buonarroti is made chief architect of St. ...

Microorganisms were first directly observed by Anton van Leeuwenhoek, who is considered the father of microbiology. Anton van Leeuwenhoek Anton van Leeuwenhoek (October 24, 1632 - August 30, 1723, full name Thonius Philips van Leeuwenhoek (pronounced Layewenhook) was a Dutch tradesman and scientist from Delft, Netherlands. ... An agar plate streaked with microorganisms Microbiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. ...

The Italian Agostino Bassi is often credited with having stated the germ theory of disease for the first time, based on his observations on the lethal and epidemic muscardine disease of silkworms. In 1835 he specifically blamed the deaths of the insects on a contagious, living agent, that was visible to the naked eye as powdery spore masses; this microscopic fungus was subsequently called Beauveria bassiana in his honor. Agostino Bassi. ... Binomial name Beauveria bassiana (Bals. ... Binomial name Bombyx mori Linnaeus, 1758 For the band named Silkworm, see Silkworm (band). ... Binomial name Beauveria bassiana (Bals. ...

Italian physician Francesco Redi provided proof against spontaneous generation. He devised an experiment where he used three flasks. He placed a meat loaf in each of the three flasks. He had one of the flasks open, another one tightly sealed, and the last one covered with gauze. After a few days, he observed that the meat loaf in the open flask was covered by maggots, and the flask covered with gauze had maggots on the surface of the gauze. However, the tightly sealed flask had no maggots inside or outside it. He also noticed that the maggots were only found on surfaces that were accessible by flies. From this he concluded that spontaneous generation is not a plausible theory. Redi is featured in many modern-day science textbooks due to his experiment. ... Abiogenesis, in its most general sense, is the hypothetical generation of life from non-living matter. ...

John Snow contributed to the formation of the germ theory when he traced the source of the 1854 cholera outbreak in the Soho neighbourhood of London. The statistical analysis of the affected cases showed that the outbreak was not consistent with the miasma theory which was prevalent at the time. Contrary to the contagion model, he identified drinking water as the vessel for transmission of the disease. He found that cases occurred in the homes which obtained their water from the Broad Street pump, which, not coincidentally, was at the center of the outbreak. Dr. Vagina Face John Snow (16 March 1813 - 16 June 1858) was a British physician and a leader in the adoption of anaesthesia and medical hygiene, and is considered one of the fathers of epidemiology for his work in tracing the source of a cholera outbreak in Soho, Westminster, England... Cholera (or Asiatic cholera or epidemic cholera) is a severe diarrheal disease caused by the bacterium Vibrio cholerae. ... The miasmatic theory of disease held that diseases such as cholera or the Black Death were caused by a miasma (Greek language: pollution), a noxious form of bad air. In general, this concept has been supplanted by the more scientifically founded germ theory of disease. ... Broadwick Street showing the John Snow memorial and pub Sited at the junction of Broad Street (today Broadwick Street) and Cambridge Street (today Lexington Street) in Soho, London W1, close to the rear wall of what is today is the John Snow pub. ...

Louis Pasteur further demonstrated between 1860 and 1864 that fermentation and the growth of microorganisms in nutrient broths did not proceed by spontaneous generation. He exposed freshly boiled broth 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. Louis Pasteur (December 27, 1822 – September 28, 1895) was a French chemist best known for his remarkable breakthroughs in microbiology. ... For other uses, see Fermentation. ...

Robert Koch was the first scientist to devise a series of proofs used to verify the germ theory of disease.^[1] Koch's Postulates were first used in 1875 to demonstrate anthrax was caused by the bacterium Bacillus anthracis. These postulates are still used today to help determine if a newly discovered disease is caused by a microorganism. For the American lobbyist, see Bobby Koch. ... Kochs postulates (or Henle-Koch postulates) are four criteria designed to establish a causal relationship between a causative microbe and a disease. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Binomial name Bacillus anthracis Cohn 1872 Bacillus anthracis is a Gram-positive, facultatively anaerobic, rod-shaped bacterium of the genus Bacillus. ...

Reception

"Science proceeds by the death of scientists", and although Pasteur's demonstration essentially solved the question, the germ theory was not universally immediately accepted. The germ theory of disease was a theoretical foundation of epidemiology, the development and use of anti-microbial and antibiotic drugs, further vaccines after they empirically derived one for smallpox, hygienic practices in hospitals, and public sanitation. The germ theory provided a rationale for some existing practices and enabled others to be established. Epidemiology is the study of factors affecting the health and illness of populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine. ... Staphylococcus aureus - Antibiotics test plate. ... A bottle and a syringe containing the influenza vaccine. ... Hygiene refers to practices associated with ensuring good health and cleanliness. ... Public is of or pertaining to the people; belonging to the people; relating to, or affecting, a nation, state, or community; opposed to private; as, the public treasury, a road or lake. ... E. Coli bacteria under magnification Sanitation is the hygienic disposal or recycling of waste, as well as the policy and practice of protecting health through hygienic measures. ...

Criticism

Though no one seriously disputes the germ theory outright, there are some who believe that it is incomplete as a theory of disease. The most commonly cited reason is the clinical inaccuracy of Koch's third postulate, which states that any susceptible animal infected with a pathogenic microbe should express symptoms. Koch himself later recanted this postulate after evidence showed asymptomatic carriers of typhoid and cholera. Kochs postulates (or Henle-Koch postulates) are four criteria designed to establish a causal relationship between a causative microbe and a disease. ... This is about the disease typhoid fever. ... Cholera (or Asiatic cholera or epidemic cholera) is a severe diarrheal disease caused by the bacterium Vibrio cholerae. ...

Others' theories of disease accentuate the host resistance factors, arguing that germs are too ubiquitous to be viewed as the "cause" of disease, even if they are a necessary component of disease. These approaches typically accept the mechanics of the germ theory, but emphasize that heredity, public health, socioeconomic status, nutritional and/or immunologic status, or lifestyle are more important than germs themselves. Many people with same or similar exposure to same microbes, may not all get similar infection and outcome under normal environment. It can be immune defense strength dependent. But immune strength, susceptibilities and sensitivities related to particular microbes can also be dependent on instabilities and imbalances in the biochemistry of an individual. As such, it can be thought that any deviation from homeostasis can also be a reason to invite and get any infection somewhat justify "miasma" or substance based theory. See Heredity (disambiguation) for other meanings. ... Public health is concerned with threats to the overall health of a community based on population health analysis. ... Socioeconomics or Socio-economics is the study of the relationship between economic activity and social life. ... The Nutrition Facts table indicates the amounts of nutrients which experts recommend you limit or consume in adequate amounts. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ...

Outside of science, previous theories ascribing disease to supernatural or divine agents also continue to have proponents.

See also

• Rudolf Virchow

[[ Rudolf Ludwig Karl Virchow (born October 13, 1821, in Schivelbein (Pomerania); died September 5, 1902, in Berlin) was a German doctor, anthropologist, public health activist, pathologist, prehistorian, biologist and politician. ...

References

The Islamic Medical Association of North America (IMANA) is the largest Muslim medical organization in North America. ...

External links

• Germ Theory of Disease—Supplemental Lecture (98/03/28 update) by Stephen T. Abedon
• The Germ Theory Calendar by William C. Campbell
• Science's war on infectious diseases