Contingent contagionism

Contingent contagionism was a concept in 19th-century medical writing and epidemiology before the germ theory, used as a qualified way of rejecting the application of the term "contagious disease" for a particular infection. For example, it could be stated that cholera, or typhus, was not contagious in a "healthy atmosphere", but might be contagious in an "impure atmosphere".^[1] Contingent contagionism covered a wide range of views between "contagionist", and "anti-contagionist" such as held by supporters of the miasma theory.^[2]

Background

A form of contingent contagionism was standard in medieval European medicine. Contagion was not conceptualised as restricted to physical contact. A corruption of air could be transmitted from person to person, at short range.^[3]

Contagionists versus anticontagionists

By the 1840s public health policy, at least in the United Kingdom, had become a battleground between contagionist and anti-contagionist parties. The former, in particular, supported quarantine measures against epidemics (such as the cholera pandemic). The latter opposed quarantines. Anticontagionists, for example, argued that infection could be at a distance, from a cause that could be sporadic and possible diffused through the air, and taking advantage of "predisposed" individuals.^[4] Public health measures quite typically combined contagionist and anti-contagionist aspects.^[5] Anti-contagionists, such as Florence Nightingale who was a convinced miasmatist, could collaborate with contingent contagionists on sanitary measures.^[6]

The "filth theory"

Decomposing organic waste, as "filth", was considered implicated in many diseases, because of the gases it generated. The application of contingent contagionism could be that there was a contagious agent that was spread by filthy conditions. Sanitation as cleaning was therefore directly associated with public health.^[7] It has been commented that those involved in public health at this time, successful in bringing down death rates, "often attributed disease causation to levels farther up the causal chain than direct biological mechanisms".^[8]

Ventilation

The Medico-chirurgical Review in 1824 wrote that it had "always advocated" the doctrine of contingent contagion in the case of yellow fever "and indeed in most fevers". Having mentioned William Pym (contagionist) and Edward Nathaniel Bancroft (anti-contagionist) as extremists, it went on to say (italics in the original)

That the yellow fever of the West Indies [...] is rarely contagious, under common circumstances of cleanliness and ventilation, is as well ascertained as any fact in medicine.^[9]

Which it qualified in terms of overcrowding, and an outbreak in 1823 on the sloop HMS Bann.

The influence of atmosphere on contagion was subject to a distinction: a "pure" atmosphere might effectively block airborne contagion, while an "impure" atmosphere was ineffective for that; or on the other hand "impure" atmosphere, as well as crowding and filth, might mean a disease could "acquire" the property of contagion.^[10] A "malignant microenvironment" could be to blame, a hypothesis that had a consensus behind it in the aetiology of the middle of the 19th century. Inadequate ventilation was one factor to which the consensus pointed.^[11]

Zymotic theory

Zymotic theory was an explanation of disease developed by Justus von Liebig and William Farr in the 1840s. A form of contingent contagionism, it began with a hypothesis on decomposition of large complex molecules, depending on collision with other such molecules. It relied on fermentation as an underlying analogy for disease.^[12]

Notes

1. Charles Brodhead Coventry (1849). Epidemic Cholera: Its History, Causes, Pathology, and Treatment. Geo. H. Derby & Company. p. 51. Retrieved 21 June 2013.
2. Davey Smith, George. "Commentary: Behind the Broad Street pump: aetiology, epidemiology and prevention of cholera in mid-19th century Britain". International Journal of Epidemiology. 31 (5): 920–932.
3. Irina Metzler, Disability in Medieval Europe (2006) (PDF), at p. 71.
4. Michael Worboys (16 October 2000). Spreading Germs: Disease Theories and Medical Practice in Britain, 1865-1900. Cambridge University Press. pp. 39–40. ISBN 978-0-521-77302-7. Retrieved 21 June 2013.
5. ocp.hul.harvard.edu, Cholera Epidemics in the 19th Century.
6. Sandra Holton, Feminine Authority and Social Order: Florence Nightingale's Conception of Nursing and Health Care, Social Analysis: The International Journal of Social and Cultural Practice No. 15, Gender and Social Life (August 1984), pp. 59-72, at p. 60. Published by: Berghahn Books. Stable URL: http://www.jstor.org/stable/23169278
7. Jon A. Peterson (6 August 2003). The Birth of City Planning in the United States, 1840–1917. JHU Press. p. 32. ISBN 978-0-8018-7210-5. Retrieved 21 June 2013.
8. Willem Jozef Meine Martens; A. Anthony J. McMichael (2002). Environmental Change, Climate, and Health: Issues and Research Methods. Cambridge University Press. p. 55. ISBN 978-1-139-43546-8. Retrieved 21 June 2013.
9. James Johnson (1824). The Medico-chirurgical Review. S. Highley. p. 916. Retrieved 21 June 2013.
10. René La Roche (1855). Yellow Fever, Considered in Its Historical, Pathological, Etiological, and Therapeutical Relations: Including a Sketch of the Disease as it Has Occurred in Philadelphia from 1699 to 1854, with an Examination of the Connections Between it and the Fevers Known Under the Same Name in Other Parts of Temperate, as Well as in Tropical, Regions. Blanchard and Lea. p. 566. Retrieved 21 June 2013.
11. Charles E. Rosenberg (28 August 1992). Explaining Epidemics. Cambridge University Press. p. 298. ISBN 978-0-521-39569-4. Retrieved 21 June 2013.
12. Christopher Hamlin (8 October 2009). Cholera: The Biography. Oxford University Press. pp. 198–200. ISBN 978-0-19-158015-4. Retrieved 21 June 2013.