BLUE DEATH IN BENGAL - Tambora: The Eruption that Changed the World - page 46

Figure 4.4. William Hodges, The Ghauts at Benares (1787). (Royal Academy of Arts, London; Photo: John
Hammond.)
CHOLERA AND CLIMATE CHANGE
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. 24
Energized by its passage through the human intestine, the cholera microbe achieves a tem-
porary hyperinfective state. Density of human traffic is thus essential to its continued trans-
mission. Carrying the fatal microbe with them in their bowels, soldiers, pilgrims, and travel-
ing merchants in 1817 dispersed the infection to unsuspecting fresh host communities north
and west across India. In the following years and decades, these same human vectors, follow-
ing the webs of global trade, brought cholera southeast to the Dutch Indies and East Asia,
and northwest across the great trading routes of Arabia to Russia, Europe, and finally the
Americas. The eventual global death toll of nineteenth-century cholera stands in the tens of
millions.
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 in-
cludes a ninety-page prefatory description of the “distempered” state of the weather begin-
ning in late 1815. By attributing the outbreak of cholera to meteorological causes, Jameson
placed himself within an established tradition of environmentalist medical theories dat-
ing back to the Hippocratic revival of the late seventeenth century. The pathogens of dis-
ease, whether produced by the noxious exhalations of the Earth or the “vitiated” state of
the atmosphere, were airborne. The Indian cholera, Jameson concluded, had been spread
by the strangely humid atmosphere, drought, and unusual winds of 1816-17. With its de-
tailed synoptic data—based on one hundred survey reports from physicians across British In-
dia—Jameson's report is a landmark in medical and public health literature and was the most
quoted text by English writers on cholera for decades.
Already by the Tambora period, however, debates over the etiology of cholera were shift-
ing. In subsequent decades, a new legion of medical theorists of cholera would come to reject