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- The Future is Built By Our Past.
The Future is Built By Our Past.
The 1918 Influenza Epidemic and India.
We have all seen firsthand the effects of the COVID-19 pandemic. Since 2019, the SARS-CoV-2 virus has spread throughout the world, causing countless deaths and resulting in a global state of emergency. As of June 2023, the World Health Organization estimates that there have been roughly 6.9 million deaths from SARS-CoV-2 (or COVID-19). (1) However, this statistic does not include individuals from South East Asia, Africa, and the Pacific where data is sparse. Thus, many organizations speculate that the true death toll might be between 7 and 15 million. (2, 3) Many believe that the COVID-19 pandemic was the most devastating disease, perhaps since the Black Death in the 14th century. However, what if I told you there was a disease that was more deadly than SARS-CoV-2, causing the same devastation the COVID pandemic did, but upon a single country? This disease was the 1918 Influenza and between 1918 and 1920, this epidemic killed between 11 and 14 million people in India. (4)
From a pure epidemiology perspective, data suggests that the 1918 Influenza virus is less dangerous than COVID. Why is this so?
Epidemiologists tend to think about infectious disease through the value R0, which represents how fast a given disease spreads throughout a population. (5) R0 (also known as the viral/basic reproduction number) tells us roughly how many people may contract a disease from one contagious individual. (6) However, the R0 calculation makes several important assumptions, specifically that all individuals in the population must not be vaccinated and must not have contracted the disease before. The R0 value for a specific virus is calculated using three variables: how transmissible the virus is (how easily a contagious individual can pass on the illness), the rate of contact in a population (how often people are close enough to transmit the virus), and the infectious period duration (how long someone is contagious with the virus). (7) In general, a virus with R0 > 1 is likely to spread and a virus with R0 < 1 is likely to die out quickly.
How does this relate to SARS-CoV-2 and the 1918 Influenza epidemic? Below, I include a graph showing the R0 values/relative contagiousness of different diseases. (8)
The data shows that the Influenza of 1918 has a significantly smaller reproduction number (R0) than SARS-CoV-2. R0 for COVID-19 has been estimated to be between 2 and 3 with the Delta Variant being the most contagious variant (R0 between 5 and 7). (9) On the other hand, the R0 for the 1918 Influenza has been estimated to be between 1.4 and 2.8. (10) The data also shows that the Influenza of 1918 was significantly less contagious than many other viruses including Measles, Rhinovirus, HIV, and Smallpox. While many of these viruses also resulted in widespread epidemics, what made the 1918 Influenza so dangerous?
Below, I include a timeline of the 1918 Influenza Epidemic in India.
While the Influenza pandemic began in Europe in May of 1918, the first cases were only reported in India in June. The virus entered India through the ports of Mumbai, a major trade city, and spread inward. It destroyed highly urban communities while spreading throughout the nation. In September, the second wave began as the influenza virus mutated, becoming even more deadly. This second wave proved to be the most severe in India and the nation experienced a peak in mortality in October. Although a third wave began in December, cases continued to decline and the nation began to recover in 1919.
Public health professionals are always looking to identify how a virus spreads within a population over time. Understanding disease flow can inform health policy, decreasing contagion and rapidly decreasing viral load within a population. Using differential equations, compartmentalization, and computer modeling, we can develop strategies to calculate disease flow over time. (11) One such model is the SIR (Susceptible-Infectious-Recovered) model which calculates the percent of a population that is infected, susceptible to disease, and recovered from disease over time. (12) More models have been built including the SEIR (Susceptible-Exposed-Infectious-Recovered) and the SQEIR (Susceptible-Quarantined-Exposed-Infectious-Recovered), that use different parameters to follow disease progression as accurately as possible. (13) Prior to public health, I was interested in computer science and using algorithms to solve problems. The SIR model was one I explored when tracking the spread of 1918 Influenza in India.
The total mortality of 1918 Influenza in India was estimated to be between 10 and 20 million, primarily affecting individuals aged 20 to 40. (14) The mortality caused by this virus, approximately 6% of India's population, is roughly equivalent to the total deaths during World War 1. (15) So what made this disease so dangerous in India?
End of World War I: The Influenza virus likely entered India via troops returning from World War I. (16) Because port cities where the troops arrived were also major population centers, the virus spread quickly, infecting a large part of the Indian population within a few months.
High Population Density: India has a very high population density which enabled the Influenza virus to transmit quickly between individuals.
Lack of Infrastructure: Prior to 1918 Influenza, the Indian government had not prioritized health infrastructure. (17) In fact, at this time, less than 1.5% of India’s GDP was invested into public health, a smaller percentage than most other highly-populated nations. (18) Thus, infected individuals had few options to seek ameliorative care and susceptible individuals had little access to medical information regarding preventative measures.
Poor Individual Health: Coupled with the fact that Indian individuals tended to live in very close proximity to each other, many Indians were malnourished with weakened immune systems. (19) Additionally, poor hygiene practices including lack of access to clean water and poor waste disposal resulted in increased viral transmission.
In contrast, while the virus devastated European populations, these populations recovered faster because European governments had more established health infrastructure and because European populations were (on net) less malnourished with better hygiene.
So what did the Indian government actually do to curb the spread of 1918 Influenza? The Indian Government relied on a 5 step approach:
Mandated Quarantines: The Indian government imposed isolation periods for individuals suspected of contracting Influenza and for individuals already infected and contagious. (20) The Indian government also placed restrictions on large public gatherings (political, social, and religious) to eliminate the frequency of super-spreading events.
Travel Restrictions: The Indian government placed limits on ships entering and exiting the country, yet these restrictions had little impact on viral transmission. (21)
Sanitation Improvements: The Indian government imposed mandatory sanitation requirements. For example, in an attempt to reduce disease spread in public spaces, the Indian government attempted to prevent coughing and sneezing in outdoor spaces. (22)
Health Infrastructure: The Indian government funded the development of temporary clinics and wellness centers to provide care to infected individuals.
Health Education: The Indian government subsidized programs that focused on informing Indian individuals about the benefits of quarantines and personal hygiene.
While the Indian government did attempt to reduce the spread of 1918 Influenza, the virus devastated the Indian population, causing the only population decline in the past century. (23)
The Influenza epidemic occurred more than a century ago, and since then, we have learned much about what makes for a successful disease response and how to best use population data to influence policy. Looking back, what types of policies could the Indian government have used to stabilize this crisis?
First, the Indian government could have utilized what we now call “Early Detection and Rapid Response” plans. These policies typically consist of surveillance tools to identify infectious individuals coupled with contact tracing methods that are used to quickly identify other susceptible individuals. Combined with isolation policies like those the Indian government implemented, this strategy would have reduced viral transmission between individuals.
Second, the Indian government could have developed a coordinated response from different agencies. (24) This would have resulted in increased data sharing, providing the Indian government with more pathways to reduce viral spread in the population. Specifically, a coordinated response would have allowed the government to provide more resources to affected areas. Although some makeshift clinics were built to treat the ill, demand for more hospital beds grew exponentially during the epidemic, resulting in a severe shortage. Thus, the Indian government could have set up additional clinics to house the infected while providing short-term care.
Finally, while our first thought when we encounter a new infectious disease might be vaccines, during the early 1900s, vaccination was still considered a new science. In fact, the US developed its first influenza vaccine by 1945, when 1918 Influenza was no longer a concern. (25) Had the Indian government invested in epidemiology research, however, a short-term solution might have been found that would have contained viral spread and reduced mortality.
The COVID-19 pandemic has put a spotlight on epidemiology and public health, as these fields have become crucial in preventing death and disease spread on a global scale. Yet, rapid urbanization and climate change have made pandemics in the future a near certainty. (26) In order to combat new infectious diseases, we must look to our past, reviewing our previous missteps in order to prevent ourselves from making the same ones again at the cost of those around us.