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Cholera and Climate

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  • Location: Camborne
  • Location: Camborne

Cholera had been seasonally endemic to Lower Bengal since time immemorial. But in May 1817, when the monsoon arrived three weeks early and delivered further calamitous quantities of rain to the delta region, the perennial Bengal cholera suddenly appeared out of season, showing unusual strength and breadth. By August an unprecedented "epidemic" of the disease had spread among the Indian population. A short month later an official report declared cholera to be "raging with extreme violence" through both the Indian and European populations of Bengal but also embarking on an unprecedented outward course to the north and west, following the river.


Death counts were hazy, perhaps inflated, and suspiciously round. Certainly thousands, perhaps tens of thousands, died in the first season. By the 1830s, at the beginning of the global cholera panic, European estimates of Indian fatalities since 1817 would run into the millions, although the numbers are impossible to verify.


Speculation as to the cause of this disaster was rife. Endemic cholera in Bengal had traditionally been associated with the "winter" months of November to January, with a smaller peak in the hot, dry months of April and May. The reach of the disease remained limited, in any given year, for the simple reason that it soon ran out of fresh victims. Explanations for the unprecedented epidemic outbreak in Bengal in 1817 depend upon the putative emergence of a new strain- of cholera capable of bypassing the built-up immunity of its indigenous hosts, then spreading rapidly to successive populations in various directions.


The "father of British medical writers on cholera;' Calcutta physician James Jameson, traced the cause of the 1817 cholera to abnormalities in the Bengal climate in the two-year period leading to the outbreak. His classic 1820 report to the Calcutta Medical Board includes a ninety-page prefatory description of the "distempered" state of the weather beginning in late 1815.


Already by 1817, however, debates over the etiology of cholera were shifting. In subsequent decades, a new legion of medical theorists of cholera would come to reject Jameson's meteorological emphasis in favor of an emerging liberal paradigm that captured the imaginations of progressive physicians and public officials through the Victorian age. Infectious disease was not "natural" but rather the product uct of human-created filth, of the open sewers and fetid air of slums and industrial tenements. Cholera was a social disease, an index of failures by nation-states to regulate and sanitize their colonial ports of trade and booming industrialized cities.


Now, however, at the beginning of the twenty-first century, the medico-meteorological worldview of James Jameson has experienced a second coming. The post-Victorian bacteriological consensus on cholera has been overtaken by a new, more complex etiological paradigm that restores credibility to the early nineteenth-century model of climatic disease dynamics.


In a series of articles, University of Michigan ecologist Mercedes Pascual has explicitly revisited the early nineteenth-century debate between meteorological and contagionist theories of cholera, proposing to "integrate" them and thereby return medical science full circle to an understanding of"the influence of climate on disease dynamics?' Pascual's theoretical ecology of cholera has shown "interannual variability" of climate-that is, weather anomalies such as drought, flood, and unseasonable temperatures-to be a strong driver of outbreaks. In addition to threatening the security of water infrastructure, excessive rainfall alters the salinity levels of water and promotes the growth of nutrients conducive to bacterial production. Conversely droughts, by increasing the temperature of reduced standing bodies of water and concentrating the bacterial population, also promote disease transmission.




Gillen D’Arcy Wood, Tambora: The Eruption that Changed the World, Princetown University Press,


Cholera and climate: revisiting the quantitative evidence


Mercedes Pascual, Menno J. Bouma, Andrew P. Dobson



Cholera dynamics in endemic regions display regular seasonal cycles and pronounced interannual variability. We review here the currentquantitative evidence for the influence of climate on cholera dynamics with reference to the early literature on the subject. We also brieflyreview the incipient status of mathematical models for cholera and argue that these models are important for understanding climaticinfluences in the context of the population dynamics of the disease. A better understanding of disease risk related to the environment shouldfurther underscore the need for changing the socioeconomic conditions conducive to choler



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