Between 1817 and 1920, the pandemics of cholera, plague and influenza killed over 70 million people, more than those killed by wars in that period (Tumbe 2020b). As I have shown in my recent book, this impact was mostly in Asia and the country most affected in each of the three pandemics was India where over 40 million perished. In this brief article, I highlight the various ways ‘seasonality’ mattered in those three pandemics.
The role of seasonality in the spread of cholera, plague and influenza
A virulent form of cholera broke out in eastern India in 1817 and in a few decades it overwhelmed the world to be the most feared disease of the 19th century (think of García Marquez’s novel Love in the Time of Cholera to dub that era). Once cholera was shown to be water-borne in the 1850s, piped water systems and better sanitation cut mortality rates in Europe and northern America but continued to ravage the Indian subcontinent for five more decades. Why? British colonial officials in India refused to accept the water-borne theory for decades because cholera was distinctly seasonal in India (see chart below). It was a medical whodunit then and in some ways, it still is, though recent research on cholera shows how environmental factors can play a part in influencing the virulence of cholera (Hamlin 2009). Nevertheless, cholera mortality rates fell in the 20th century most likely because prevention strategies based on its water-borne nature were adopted (see also earlier articles on progress against disease in this blog here and here).
Plague devastated China and India in the late 19th and early 20th century. Over 12 million died in India alone between 1896 and 1920. While the British colonial officials in India first focused on curbing plague through disinfectants, isolation and segregation, they soon abandoned these strategies and accepted the traditional Indian wisdom of temporary evacuation. This was based on observations by locals that the chances of plague were reduced if one left their houses at night and camped out in the open and that plague never lasted for too long in the year disappearing with the onset of the monsoon (June-Sep). Both these strategies were later shown to have scientific validity, as they affected the human-rat flea engagement via light and humidity. The chart below shows the seasonality of plague in India and its virtual disappearance all over during the monsoon in July.
The devastating influenza pandemics of 1918-20 took its largest toll in the Indian subcontinent where I estimate 20 million people died (Tumbe 2020b). Why did so many people die in India and why did so many die particularly in western and northern India? The deadly second wave of the influenza pandemic in late 1918 coincided with India’s third worst drought in recorded history which created acute food shortages in some districts. Price distortions were large with 30% food-grain inflation in the drought-hit districts in western and northern India as against deflation in eastern India. I argue that people in western and northern India took on influenza with severe malnutrition and thereby succumbed to it. One way to understand this is by pointing out that large droughts in India caused famines in the subsequent year as it took a while for food stocks to plummet.
For instance, the rainfall shocks of 1877 and 1899 (see chart above) led to famine mortality in Berar in central India in 1878 and 1900 respectively, but the drought of 1918 coincided with the mortality spike in the same year because of the raging influenza pandemic (see chart below). District level analysis shows indeed that it was the drought-hit districts that suffered higher mortality. After 1920, better health systems and enhanced food production and connectivity have avoided such mortality disasters after acute droughts.
Seasonality and long-run health
In all three pandemics, seasonality mattered decisively. In the case of cholera, the over-reaction by public health officials to the seasonality witnessed in India, and the stubbornness to stick with an outdated scientific paradigm led to the needless deaths of millions over the next few decades. In the case of plague, the appreciation of seasonality by locals eventually won over health officials who began recommending temporary evacuation strategies, that saved many lives. And while influenza as a disease was not necessarily seasonal in 1918, it was particularly devastating in India because it coincided with a drought in the key monsoon season. Understanding seasonality of diseases and other elements that drive nutrition during the year appears to be an important aspect in long run matters of health.
- Dyson, T. 1989. “The Historical Demography of Berar, 1881-1980.” In T. Dyson (Ed.), India’s Historical Demography: Studies in Famine, Disease and Society (pp. 150-196). London: Curzon Press.
- Hamlin, C. 2009. Cholera: The Biography.
- Hwa-Lung Yu and George Christakos, ‘Spatiotemporal Modelling and Mapping of the Bubonic Plague Epidemic in India,” International Journal of Health Geographics, 5 (12) (2006), 1-15.
- Pollitzer, R. 1959. Cholera. Geneva: World Health Organization.
- Tumbe, C. 2020a. The Age of Pandemics, 1817-1920: How they Shaped India and the World. Noida: Harper Collins.
- Tumbe, C. 2020b. ‘Pandemics and Historical Mortality in India’, IIMA Working Paper 2020-12-03. Indian Institute of Management Ahmedabad.
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