Skip to main content

Miasma Theory


Miasmas are poisonous emanations, from putrefying carcasses, rotting vegetation or molds, and invisible dust particles inside dwellings. They were once believed to enter the body and cause disease. This belief dates at least from classical Greece in the fourth or fifth century b.c.e., and it persisted, alongside other theories and models for disease causation, until the middle of the nineteenth century. To some extent the belief still persists today. It was most clearly enunciated by Italian physician Giovanni Lancisi (16541720) in De noxiis paludum effluviss (Of the poisonous effleuvia of malaria, 1717).

The miasma theory was advanced to explain many important diseases, including tuberculosis and malaria (from mala aria, meaning "bad air"). Many eminent leaders of medical opinion were convinced that the cholera epidemics of the nineteenth century were caused by miasmas, even as the evidence mounted for the germ theory, which was gathering momentum at that time. William Farr stated firmly in his annual report on vital statistics in Great Britain in 1852 that the inverse association of cholera mortality with elevation above sea level confirmed the miasma theory as its cause. Farr rejected John Snow's argument, based on evidence and logical reasoning, that cholera was caused by contaminated drinking water. Though the miasma theory soon proved to be a wrong explanation for the cause of cholera, it was partially sustained as an explanation for malaria. Some malaria control measures based on miasma theory, particularly draining swamps and marshes, are part of modern control strategies; though not, of course, because miasmas cause malaria, but because mosquito breeding sites are eliminated.

John M. Last

(see also: Farr, William; Snow, John; Theories of Health and Illness )

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Miasma Theory." Encyclopedia of Public Health. . 22 Mar. 2019 <>.

"Miasma Theory." Encyclopedia of Public Health. . (March 22, 2019).

"Miasma Theory." Encyclopedia of Public Health. . Retrieved March 22, 2019 from

Learn more about citation styles

Citation styles gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

The Chicago Manual of Style

American Psychological Association

  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.