There was much debate in the middle of the nineteenth century about the origin of diseases.  Although many British physicians thought that smallpox, measles, and syphilis were contagious, opinions were more divided on cholera, typhus and typhoid -- the most feared epidemic diseases.  Thomas Wakley, editor of The Lancet, captured the confusion on cholera in an 1853 editorial when he raised the question, What is cholera?:

...all is darkness and confusion, vague theory, and a vain speculation.  Is it a fungus, an insect, a miasm, an electrical disturbance, a deficiency of ozone, a morbid off-scouring from the intestinal canal?  We know nothing; we are at sea in a whirlpool of conjecture.

- Wakley T. The Lancet II, 393, 1853

During this time there were three main theories to explain infectious diseases in general and cholera in specific.


The most widely accepted notion of infection was the miasma theory. It held that under certain circumstances, air became charged with an epidemic influence which in turn became malignant when combined with the emissions of organic decomposition from the earth. The resulting gases or miasms produced diseases.  Supporters of the miasma theory felt that cholera was one such condition caused by noxious odors of decayed matter. 

The miasma theory was very appealing to English sanitary reformers.  It explain why diseases were epidemic in the undrained, filthy and stinking areas inhabited by the poor. The existence of miasms was central to the orthodoxy of the new public health movement, focusing attention on environmental problems rather than on those of personal health and infection.  Included as supporters were Sir Edwin Chadwick (1800-1890), the great social and sanitary reformer; William Farr (1807-83), the famous statistician; Florence Nightingale (1820-1910), the prominent nurse and hero of the Crimean War; and Sir John Simon, the first Medical Officer of Health for London.  


The second theory was that of spontaneous generation of disease within the blood.  This theory was essentially chemical, and as such, denied contagion.  The most active supporter of the theory was the German chemist Justus von Liebig (1803-1873) who held strong views on "fermentation" of the blood. The blood generation theory received negligible support in England.


The third notion was the germ theory, or infection was caused by a living organism, a contagium vivum.  While not new, the theory was well formulated by the German pathologist Friedrich Henle (1809-85) who wrote in 1840: 

The material of contagions is not only an organic but a living one and is indeed endowed with a life of its own, which is, in relation to the diseased body, a parasitic organism.

- Henle, FGJ. Von den Miasmen und Contagien und von den miasmatisch-contagiösen Krankheiten, 1840

This theory for cholera was supported by observations and epidemiological studies of John Snow (1813-58) in London and William Budd (1811-80) in Bristol, England. The supporters of the miasma theory were unconvinced by Snow's and Budd's findings due to the absence of an organism and the lack of conclusive experimental proof.  While the organism (Vibrio cholerae) had been discovery in 1854 by Italian anatomist Fillipo Pacini, nearly all English scientists and physicians were unaware of his work.  

Minds changed in the early 1860s when French chemist Louis Pasteur (1822-95) demonstrated the existence of pathogenic organisms. More conclusive for the germ theory of cholera was the work of German physician Robert Koch (1843-1910), a former student of Friedrich Henle at the University of Göttingen. Koch in 1884 rediscovered, isolated and cultured Vibrio cholerae. The findings were circulated worldwide, following a famous dispatch to the German government and German press emanating from Calcutta, India.  

The germ theory for cholera was finally established, although earlier changes in the sanitary environment, called for by the erroneous miasma theory, had actually done much to reduce the transmission of disease. London provides an example of how useful a wrong theory (miasma) can be for addressing an epidemic (improvement of air, solid waste and water supplies), in this example cholera.  While the sanitary reforms following the miasma theory were effective at containing cholera, full acceptance of the scientifically valid germ theory would have saved even more lives. 


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