Between January of 1918 and December of 1919, the H1N1 strain of influenza raced around the world, infecting some 500 million people.  An estimated 50 to 100 million people died, making it the worst pandemic since the Black Death that ravaged medieval Asia and Europe.  In 1918-19, the highest toll for any single country was in India, then a British colony, where a shocking 13 to 19 million people died of the flu.

The 1918 flu's symptoms were so extreme that it was often initially misdiagnosed.  Doctors believed that they were dealing with cholera, typhoid, or dengue fever. Worldwide, this strain killed approximately 20% of the people who caught it; the fatality rate in a typical flu season is 0.1%.

The influenza first arrived on Indian shores at the city of Bombay (Mumbai) on June 10, 1918.  Seven Indian police officers who patrolled the docks became ill with a non-malarial fever and were hospitalized. By the 19th, shops and offices around the cities closed down as thousands of sickly employees stayed home from work.  By early July, the city had 230 deaths per day, and almost every home had at least one family member sick with the influenza. On June 20, a hospital ship full of flu victims docked in Karachi (now in Pakistan), introducing the pandemic there.

By mid-July, the flu had spread across the Punjab. This first wave would take about 1,600 lives in India. In September, an even deadlier second wave of influenza got started in the Deccan.

  It struck western, central, and northern India, leaving local people and British administrators at a loss to cope with the pandemic.  To make matters worse, many trained medical professionals were out of the country, serving with the military in World War I.  By December of 1918, well over 1 million Indian people were dead just in the region controlled by the Bombay Presidency.

In major cities such as Bombay, however, public health officers and charity organizations rushed to raise funds, set up temporary hospitals, distribute the vaccine once it was created, and distribute other medications.  The vast majority of Indian flu victims lived out in the countryside, however, and rural India saw no comparable efforts due to lack of resources and infrastructure.

Why was the flu so deadly in India?  Mortality rates there seem to have been higher than anywhere else on Earth.  Theories to explain this abound, and sometimes contradict one another.  For example, the US National Oceanic and Atmospheric Administration (NOAA) suggests that the strong 1918 El Nino climate event may have contributed to the high death rate in India. The El Nino disrupted the monsoon rains and led to a drought across southern and central India; NOAA theorizes that people weakened by hunger were more susceptible to the influenza.

Kenneth Hill, however, finds that the influenza was deadliest at higher altitudes in the northern and northwestern part of India, where the atmosphere was damper.  He suggests that the influenza virus was able to survive better in aerosol droplets from victims' coughs in the more humid conditions of northern India.

Coming at the end of the bloody and horrific Great War, the 1918 Flu struck a British Empire that was almost unable to comprehend. As Andrew Balfour and Henry H. Scott remark in their 1924 work Health Problems of the Empire, p. 218: "[T]he whole Empire was affected.  We were so surfeited with horrors, so inured to death and suffering, that the true magnitude of the disaster was never appreciated."

Sources:

Compo, Gilbert, Prashant Sardeshmukh, et al. "New Look at 1918/1919 El Nino Suggests Link to Flu Pandemic," NOAA website, accessed October 26, 2014.

Hill, Kenneth. "Influenza in India 1918: Epicenter of an Epidemic," Harvard Center for Population and Development Studies, accessed October 26, 2014.

Killingray, David. "The New 'Imperial Disease': The Influenza Pandemic of 1918-19 and Its Impact on the British Empire," Caribbean Quarterly, Vol. 49, No. 4 (Dec. 2003), pp. 30-49.

Taubenberger, Jeffery and David Morens. "1918 Influenza: The Mother of All Pandemics," Emerging Infectious Diseases, Vol. 12, No. 1 (January 2006).