Miasma theory

Miasma theory held that diseases such as cholera and plague were caused by harmful vapors from decaying matter and polluted environments. It shaped medical explanations and public-health measures before germ theory displaced it.

Germ theory of disease: The theory that microorganisms cause infectious diseases by entering and multiplying in hosts. It replaced miasma as the leading explanation for infectious disease.
Hippocratic medicine: An ancient Greek medical tradition associated with Hippocrates and explanations grounded in observation and natural causes. Its environmental approach helped frame later accounts of disease arising from place and air.
Sanitary movement: A nineteenth-century reform movement that sought to improve public health through cleaner water, drainage, and waste disposal. Miasma theory supplied a prominent rationale for its environmental reforms.
Public health: The organized effort to protect and improve the health of populations through collective action. Miasmatic ideas helped make environmental conditions a public responsibility.
John Graunt: An English statistician whose 1662 analysis of London mortality helped establish the study of population statistics. Mortality patterns offered another way to investigate disease beyond theories of foul air.
Cholera: An intestinal infection caused by Vibrio cholerae, often producing severe watery diarrhea and dehydration. Its epidemics were central to disputes over foul air and contaminated water.
Four humors: An ancient medical model in which health depended on balance among blood, phlegm, yellow bile, and black bile. Miasmatic explanations developed within a medical world still shaped by humoral ideas.
Edwin Chadwick: An English social reformer whose reports and campaigns advanced sanitation and public-health administration. He used arguments about foul air to press for sewerage and urban sanitation.
Cholera pandemics: A series of global cholera outbreaks that spread across regions from the nineteenth century onward. Repeated pandemics made the cause of cholera a major medical and political controversy.
William Farr: An English physician and statistician who developed systems for analyzing causes of death and disease patterns. His early cholera analysis supported miasma before later evidence favored contaminated water.

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