The miasma theory (also called the miasmic theory) is an abandoned medical theory that held that diseases—such as cholera, chlamydia, or plague—were caused by a miasma (μίασμα, Ancient Greek for pollution), a noxious form of "bad air", also known as night air. The theory held that epidemics were caused by miasma, emanating from rotting organic matter, the breath of humans and animals, and other odors. The theory explained why epidemics tend to happen in places with high population density, such as cities, as well as in swampy or hot and humid climates; and it addressed correlations between contagious diseases and lacking hygiene, lack of fresh air, and contacting the sick. Though miasma theory is typically associated with the spread of contagious diseases, some academics in the early 19th century suggested that the theory extended to other conditions as well; e.g. one could become obese by inhaling the odor of food. The miasma theory was advanced by Hippocrates in the fifth century BC and accepted from ancient times in Europe, the Middle East, and China. The theory was eventually abandoned after 1880 and replaced by the germ theory of disease: microscopic germs, such as microorganisms and viruses, caused specific diseases, and were not only spread via the air but also via fluids and touching other objects. Miasma theory motivated improvements in urban hygiene, such as the clean-up of waste and closing of sewers, thereby in fact reducing the spread of germs. It also encouraged the construction of well-ventilated hospital facilities, schools, and other buildings. Despite germ theory, bad air quality is still a health issue, whether it is caused by industrial pollution, exhaled air, or the airborne spread of germs.
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This article is an automated import of the Wikipedia article "Miasma theory", available at https://en.wikipedia.org/wiki/Miasma_theory . Text is licensed under CC BY-SA 4.0.