Concepts of Contagion and Epidemics
Fighting the Pneumonic Plague in Manchuria, Under the Red Cross Flag at Home and Abroad. From the holdings of Harry Elkins Widener Memorial Library—Harvard College Library.
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The concept of “contagion,” together with the concept of “contagiousness,” is thousands of years old. The meanings of both the word and the concept have changed over time. Two of the oldest diseases associated with contagiousness are leprosy, which is mentioned in the Hebrew Bible, and smallpox. Historically, both the plague and syphilis were believed to be contagious.
Before the late 19th century, many diseases that we now know to be contagious (such as cholera and tuberculosis) were considered non-contagious by educated physicians. In fact, in many cases, a belief in contagiousness was associated with folk traditions and unsophisticated laypeople.
The Causes of Contagion: An Historical View
Modern germ theory, developed between 1870 and 1900, associates most diseases with specific entities. But earlier systems of medicine held the belief that one disease could change into another or might manifest itself differently in different people.
Diseases—both individual and epidemic—did not result from action on the human body by a disease-causing agent, but, instead, were the results of individual susceptibilities and individual interactions with the environment. In turn, these considerations were often affected by the education, moral values, class, and politics of physicians and the societies in which they lived.
Explaining Disease Transmission Before the Germ Theory
It has always been the case that not everyone exposed to a particular germ gets sick, and that some people are more likely to become ill than others. Certain kinds of sickness are associated with particular places, such as the tropics, or with certain times of the year, such as the summer. Some socioeconomic groups shoulder very different disease burdens than others, even within the same society. The disease burden in urban areas can be different from the disease burden in a rural environment. A person infected with a disease germ can spread it to others, but may not show any sign of the disease.
For hundreds of years prior to the acceptance of germ theory, public health officials, scientists, physicians, and other writers had been observing and explaining the incidence and prevalence of health and disease without any awareness of disease-causing microorganisms. The Contagion collection includes a significant number of these works.
Miasmas, Zymosis, and Bad Smells
Before the last decades of the 19th century, disease was often assumed to be caused by the airborne emanations of rotting plant and animal matter, filth, and decay. These emanations were sometimes known as “miasmas.” A miasma could be local, or it could be associated with a large geographic area. A miasma could also be the temporary result of some disturbance, or it could be permanently associated with a particular place, such as a swamp. (As an example, malaria—a word that means “bad air”—was long associated with proximity to swampy environments.) Miasmas could be altered by changes in weather, season, humidity or dryness, composition of the soil, or makeup of plant species in a particular area.
Zymotic diseases were associated with fermentation, which could generate what were sometimes called “organic poisons”—tiny bits of animal or vegetable matter that could transmit disease through personal contact.
Bad smells associated with filth and decay were considered to be an essential part of their infectiousness, so eliminating the source of a bad smell could also be associated with removing a source of disease.
To become infected at all, however, a person’s humoral makeup, or “constitution,” had to be imbalanced in a way that made that person susceptible to the infection in the first place. Imbalance involved not only the bodies of individual people but also each person’s relationship to his or her environment.
Contingent Contagionism, Seasoning, and Climate
Sometimes a disease was considered contagious in some circumstances but not others. Or it might be viewed as contagious only to individuals or groups. This is sometimes known as “contingent contagionism.”
The related concept of “seasoning” arose during the periods of European colonialism and American westward expansion—roughly between the 15th and 19th centuries. Newcomers to particular climates or geographic regions were observed to become sick more readily than more “seasoned” individuals who had lived in a given area or climate over time. Once newcomers were “seasoned,” they would no longer become ill so easily.
Sin and Morality
Ideas relating sickness to personal morality have long been important in European and American thought. In the Judeo-Christian tradition, sickness has often been seen as divine punishment for sin. Cures for sexually transmitted diseases, including syphilis, have been criticized in the belief that cures would encourage immoral behavior. Moral and ethical issues associated with sex, food, drink, work, and emotions have also been connected with the possibility of contracting or spreading disease.
Puerperal Fever
Puerperal, or “child-bed” fever—a post-childbirth infection that often caused fatal septicemia in the mother—was not considered contagious until the late 19th century, even though some lying-in hospitals experienced epidemics with nearly 100% mortality.
In 1843, Oliver Wendell Holmes proposed that physicians, who typically did not wash their hands or change their clothes as they worked, were transmitting the disease from patient to patient. His idea was ridiculed.
In 1844, Ignaz Semmelweis noticed that women who gave birth at home or who delivered in his hospital with the help of midwives, rather than physicians, rarely contracted puerperal fever. He noted cases in which physicians had completed autopsies on patients dead of puerperal fever and then attended births without washing their hands. Midwives were not allowed to perform autopsies. Semmelweis experimented with various cleaning methods and the puerperal fever rate in his ward dropped signifcantly. His work was also ridiculed by physicians.
Heredity and Race
Reasons related to race and ethnicity have long been employed in explaining why particular individuals or groups become sick or appear to be resistant to certain diseases. Race and ethnicity have also been used as the basis to scapegoat particular groups for causing epidemics.
After the Germ Theory
Though the germ theory brought many fundamental changes to the understanding of diseases and epidemics, society has continued to assess contagious diseases in terms of ideas that have a much longer history. Personal susceptibilities, cleanliness, morality, social environments, race, heredity, gender, and politics continue to play a prominent role in explanations of contagion, diseases, and epidemics.
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Selected Contagion Resources
This is a partial list of digitized materials available in Contagion: Historical Views of Diseases and Epidemics. For additional materials on the topic “Concepts of Contagion and Epidemics,” click here or search the collection’s Catalog and Full Text databases.
Web Pages
Manuscripts
Records of the American Academy of Arts and Sciences, 1775–1800
“Considerations on the methods by which the sickening and pestilential exhalations from dead animal
and vegetable substances are overcome,” by Samuel L. Mitchell, June 5, 1800.
Publications
Explaining Disease Transmission Before the Germ Theory
Miasmas, Zymosis, and Bad Smells
Contingent Contagionism, Seasoning, and Climate
Sin and Morality
Puerperal Fever
Holmes, Oliver Wendell, 1809–1894. The Contagiousness of Puerperal Fever. Boston: Boston Society for Medical Improvement, 1843.
Heredity and Race
Atkinson, I. Edmondson (Isaac Edmondson). Early Syphilis in the Negro. Baltimore: J.H. Foster, [1877].
References
The following sources were used in writing this page.
Ackerknecht, Erwin. “Anticontagionism Between 1821 and 1867.” Bulletin of the History of Medicine, 22 (1948), 562–93.
Baldwin, Peter. Contagion and the State in Europe, 1830–1930. Cambridge: Cambridge University Press, 2005.
Barnes, David S. The Great Stink of Paris and the Nineteenth–Century Struggle Against Filth and Germs. Baltimore: Johns Hopkins University Press, 2006.
Barnes, David S. The Making of a Social Disease: Tuberculosis in Nineteenth-Century France. Chicago: University of Chicago Press: 1995.
Cooter, Roger. “Anticontagionism and History’s Medical Record.” In Peter Wright and Andrew Treacher, Eds., The Problem of Medical Knowledge: Examining the Social Construction of Medicine, pp. 87-108. Edinburgh: Edinburgh University Press, 1982.
Delaporte, Francois, trans. Arthur Goldhammer. Disease and Civilization: The Cholera in Paris, 1832. Cambridge, MA, and London: MIT Press, 1986.
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