Contagion and Moral Purity
Written by Nancy Selwood-Metcalfe
Edited by Marc Casey Staiano
Historically, humans have been afflicted by a plethora of illnesses, but examining how these infectious diseases were perceived across civilizations reveals our changing perceptions of illness itself.
Before modern microbiology, diseases were strongly linked to morality on account of limited understanding of what caused widespread illness and death. Illness was often explained through the concept of miasma, which linked disease to polluted or corrupted air (1). Miasma was associated with filth and decay thought to contaminate the air rather than the poor sanitation that produced it (1). In Ancient Greek, the term ‘miasma’ could also refer to the consequences of immoral acts such as murder, which might bring misfortune or plague as punishment from the gods. Contagions therefore blurred the line between physical infection and moral corruption. For thousands of years, disease was interpreted through both biological and moral frameworks, connecting illness with moral impurity or social disorder (1).
Photo from Polina Tankilevitch. Curated by Julia Leavitt (jal569@cornell.edu).
Despite early recognition of disease transmission in the Hippocratic era, the germ theory—that microorganisms cause disease—was not validated until the mid-19th century (2,3). Medical institutions relied heavily on ancient authorities, evidence for microorganisms was limited, and physicians struggled to link them directly to disease (4). Competing explanations for illness included witchcraft, demons, gods, comets, earthquakes and especially miasma (2). Industrialisation and urbanisation accelerated the spread of infectious diseases because of crowded living conditions and poor sanitation. Even when evidence challenged miasma theory, epidemics such as cholera and yellow fever were still attributed to bad air (1). These outbreaks often occurred during hot months when city air was humid and filled with the smell of waste, garbage, and decomposing animals, reinforcing the belief that foul air caused disease (2).
Because miasma linked decay with disease, illness became associated with poverty and ‘immoral’ neighborhoods. Historically, lower-class populations were more vulnerable to disease due to poor living conditions and limited access to healthcare. Groups considered morally suspect, such as criminals or prostitutes, were therefore associated with these environments and thought to be more susceptible to disease. As a result, they were often portrayed as sources of contamination and marginalized from wider society (1). Religious traditions reinforced these connections between disease and morality, interpreting illness as divine punishment or spiritual impurity, similar to Ancient Greek beliefs (1). Physical illness could be viewed as a failure of moral or religious conduct. In the Bible, for example, leprosy is repeatedly associated with ritual impurity and social exclusion (1,2). Social hierarchy and religious beliefs therefore reinforced the idea that moral corruption could infect both the body and the wider community.
As these ideas of moral corruption and miasma have circulated for thousands of years, they have influenced not just medicinal practices, but also people’s day-to-day lives, including those of artists (3). The association between immorality and disease is intertwined with troves of literature and art across history, many of which are still devotedly studied today. Shakespeare depicts evil or moral corruption to spread like a disease in his play ‘Macbeth’ (5). Under Macbeth's rule of Scotland, the country is described as ‘sick’ as the tragic hero’s immorality spreads throughout the kingdom like an illness. This can also be seen in the character Lady Macbeth, whose famous line ‘Out damned spot!’ symbolises moral contamination after an evil deed, as she obsessively washes her hands clean of blood (7). ‘The Picture of Dorian Gray’ by Oscar Wilde also plays with the concept of sin as physical corruption (8). Dorian's vanity and increasing immorality causes his portrait to become grotesque and decayed, spreading like an infection across the image of himself. The novel conceptualizes ideas of negative morality producing physical degeneration, similar to the Victorian urbanisation occurring at the time it was written. Miasma can also be seen in pieces of art such as ‘The Triumph of Death’ by Pieter Bruegel, a magnificent painting showing society through the plague outbreak (8). It shows the death and destruction the disease caused to the community, emphasising the fact that no social class could escape it. During the time when the piece was painted, the church was very prominent in people's beliefs, and the ideas of divine judgement were widely accepted. It can only be assumed that the artist interpreted this epidemic as punishment for human sin, reinforcing the belief that moral corruption could lead to widespread physical suffering.
Photo from Ketut Subiyanto. Curated by Julia Leavitt (jal569@cornell.edu).
Contagions have been understood both scientifically and morally throughout history. Initially, many ideas of where diseases originated from could only be believed blindly, as society understood little more than they were told. Although scientific advancement has charged humanity’s recognition of microorganisms, these past beliefs haven’t been erased and are still preserved in literature and culture through metaphors of disease and infection. Over time, our increase in epidemiological study has called attention to the importance of social and economic conditions in shaping disease patterns, and has allowed some of the blame and shame to be taken off the victims (1). Therefore, the evolution of modern science and the contagion theory illustrates the complex relationship between science, society, and morality in shaping how disease has been understood over time.
Nancy Selwood-Metcalfe ‘27 is a Biological Sciences major in the College of Agriculture and life sciences, on exchange from London for the year. She can be reached at ns2233@cornell.edu.
Sources:
Krieger N. Epidemiology emerges: Early theories and debating determinants of disease distribution—Poison, filth, class, & race 1600–1900. Epidemiology and the People’s Health: Theory and Context; Oxford University Press: New York, NY, USA. 2011:58-94.
Karamanou M, Panayiotakopoulos G, Tsoucalas G, Kousoulis AA, Androutsos G. From miasmas to germs: a historical approach to theories of infectious disease transmission. Infez Med. 2012 Mar 20;20(1):58-62.
Morabia A. Eras in Epidemiology: The Evolution of Ideas: By Mervyn Susser and Zena Stein.
DeLacy M. The germ of an idea: Contagionism, religion, and society in Britain, 1660-1730. Basingstoke: Palgrave Macmillan; 2016 Mar 5.
Macbeth’s Moral Conflict. English Works. [Accessed 2026 Mar 6]. Available from: https://www.englishworks.com.au/macbeths-moral-conflict/
Dorian Gray’s Moral Corruption and Tragic Downfall - eNotes.com. eNotes. 2026. [Accessed 2026 Mar 6]. Available from: https://www.enotes.com/topics/picture-dorian-gray/questions/hubs/dorian-grays-moral-corruption-and-tragic-downfall
Shakespeare W. Macbeth. In: Wells S, Taylor G, editors. The Oxford Shakespeare: Macbeth. 3rd ed. Oxford: Oxford University Press; 2008
Du Plessis A. Artincontext. “The Triumph of Death” by Pieter Bruegel the Elder - Art Analysis. artincontext.org. 2023. [Accessed 2026 Mar 6]. Available from: https://artincontext.org/the-triumph-of-death-by-pieter-bruegel-the-elder/
