A Brief History of Pandemics


If you have been following the news over the last few months, you might have noticed how often the word “unprecedented” is used to characterize the COVID-19 pandemic. However, although there may be no precedent for a pandemic of this scale in the information driven 21st century, epidemics, pandemics and the constant battle between humanity and microbes have always been a feature of human life on Earth. In fact, the world has faced visitations of infectious diseases that have transformed into global crises very much like COVID-19 during almost every century in the last millennium.

Although the world was a very different place even during the last such pandemic in 1918, looking back and understanding these pandemics and their short term and long term implications on public health, economies, and society can provide valuable insights on what the aftermath of the current COVID-19 pandemic might look like.

Plague → 14th – Early 18th Century


Plague is an infectious disease caused by the bacterium Yersinia Pestis. The disease is a vector borne disease because the bacterium is exchanged between domestic rats and humans by the rat flea Xenopsylla cheopis. Once the bacterium crosses the species barrier and reaches humans, the disease is also transmitted by the human flea Pulex irritans. At the onset of a plague outbreak, these fleas infect and kill countless rats before then causing either Bubonic, Septicemic or Pneumonic Plague in humans depending on how the bacterium enters the human body.

The dramatic symptoms caused by these three forms of the disease, which lead to a case fatality rate between 50% and 80% has transformed the very word “plague” into one that’s synonymous with calamity and the worst possible disaster. Since fleas are most active during warm weather, humanity has experienced a cycle of recurring epidemic waves of the disease that lasted for centuries and were of immense public concern between the 13th and early 18th centuries. Just like with COVID-19, each of these visitations caused major economic downturns as economic activity declined and labor forces shrank. The onset of a plague epidemic also often led to counterproductive mass migration from urban areas to rural areas since the popular explanation for the disease involved the idea that poisonous air or effluvia within a locality caused the disease.

Despite this flawed explanation for the disease however, many of the public health strategies we are using today were first developed back in the 14th century to minimize the spread of the plague. Realizing how plague outbreaks began in coastal regions and moved inwards led to a hypothesis that ships were bringing in harmful effluvia that causes the plague. Although rats aboard these ships were responsible for the outbreaks in coastal regions, this hypothesis led to the establishment of institutions called lazarettos on outlying islands off the coast of Venice. All ships arriving in Venice were directed to these lazarettos, where the cargo was unloaded, turned out in the sun, fumigated and aired. The passengers and the cargo remained at the lazaretto for forty days before they were allowed to enter the city. The duration of forty days was based on the numerous references to the number of forty in the context of purification in both the Old and New Testaments of the Bible. Nevertheless, this period of containment was termed “quarantine” after the Italian word for forty – quaranta.


Similarly, public health workers developed the first Personal Protective Equipment(PPE) made of leather and waxed fabric to minimize the spread of the plague. Other innovations like sanitary cordons enforced by the military at borders and contact tracing were also developed to mitigate the effect of plague outbreaks. Although these innovations were based on inaccurate theories backed by religious beliefs, in practice these low-tech solutions protected cities and economies from disaster to a great extent. As a result, despite the many technological advancements since the fourteenth century, these anti-plague measures developed almost a millennium ago remain as our first line of defense against an alien infectious disease like COVID-19 that lacks a cure.

The panic and fear caused by COVID-19 is leading to conspiracy theories and fake news stories that are in some cases causing violence. In the UK for example, a conspiracy theory about 5G mobile networks causing the disease has led to violent mobs setting 5G base stations ablaze. Likewise, many regarded the plague to be divine retribution for the sins committed by certain groups of people. This led to vigilante groups hunting down and in some cases even lynching scapegoats including foreigners, Jews, witches and homosexuals.

Although the plague was one of the most feared diseases in history that had a major impact on our public health strategies and societies, the disease stopped wreaking havoc by the early 18th century and disappeared by the early 19th century. Part of this phenomenon can be attributed to the increased use of soap when bathing starting in the 18th century, which reduced the prevalence of fleas and minimized human-to-human transmission. Another reason for the decline in the plague was the increased prevalence of the more aggressive brown rat(Rattus norvegicus), which led to a reduction in the black rat(Rattus rattus) population. Since the brown rat is more aggressive, the distance between humans and rats have increased, which has in turn made it harder for Y.Pestis to cross the species barrier and cause outbreaks of the plague. The development of antibiotics has also made the world far less vulnerable to a disease like the plague caused by bacterial infections.

Smallpox → 18th Century

Unlike the plague, smallpox was caused by a virus called Variola Major. Therefore, like COVID-19, the disease was mostly spread through droplets and fomites – inanimate objects contaminated with the virus. Although smallpox had a lower case fatality rate between 30 and 40 percent, it had a significant historical impact because of the fear and permanent disfigurement it caused. In his book Epidemics and Society, Frank Snowden explains that “the physicians who treated smallpox patients were convinced that this was ‘the worst of human maladies,’ and one doctor wrote in 1983 that “in the suddenness and unpredictability of its attack, the grotesque torture of its victims, the brutality of its lethal or disfiguring outcome, and the terror that it inspired, smallpox is unique among human diseases.'”

Unlike the plague however, which came in sudden outbreaks, smallpox was an ever present epidemic that afflicted humanity from the 3rd century B.C.E. with a particularly large outbreak occurring in the 18th century. As a result of the everpresent nature of smallpox, the response to the disease was very different compared to the response to the plague and even the response to the COVID-19 pandemic. Since the disease was a familiar affliction and also partly because, as an airborne disease, it equally affected the rich, it rarely caused mass hysteria, riots, scapegoating or migration to rural areas.

In addition to the fear that smallpox incited in Europe and Asia, the disease played an even more vital role than gunpowder in European expansion to the Americas, Australia and New Zealand. When the Europeans arrived on the shores of these regions along with smallpox aboard their vessels, the native population had no exposure and in turn no immunity to the disease compared the the Europeans. As a result, smallpox spread rapidly among the native peoples leading to phenomena of “virgin soil epidemics” such as the terrifying die-offs of native people in the Americas and Maoris in New Zealand. Between when Columbus arrived in Hispaniola in 1492 and 1520, the native population declined from one million to fifteen thousand. While these virgin soil epidemics were mostly unintentional, records suggest that in some cases smallpox was used as the world’s first bioweapon. For example, records indicate that the British Army officer Sir Jeffrey Amherst introduced genocide to North America when he deliberately gave blankets infected with smallpox to Native Americans in order to “reduce” them. These smallpox epidemics also led to mass immigration from Africa and the development of the slave trade and the infamous Middle Passage because Africans possessed immunity to the disease and in turn would be better for business since they would remain productive for longer.


Like the plague, smallpox also led to important public health strategies that are still in use today. The two main developments arose from the realization that people who were infected with smallpox, and recovered possessed life long immunity against the disease. Therefore, the first development called “inoculation” drew liquid from the pustule of a person infected with a mild case of smallpox and then transferred it to a person seeking immunity. Although inoculation was common in the Middle East, Asia and Europe and had a reasonable degree of success, it was risky and only accessible to the rich who could afford to stop working during the long convalescence period from the mild case of smallpox caused by the procedure.

These problems were solved through the next development, which was discovered by the English physician Dr. Edward Jenner in the 18th century. Serving in an area that produced dairy, Jenner noticed that milkmaids who got cowpox also never contracted smallpox. Since cowpox mainly affected cows, and was only a mild illness when it crossed the species barrier to humans, Jenner decided to test his theory in 1796 by having his son injected with cowpox obtained from an infected milkmaid. His theory was proven, when his son did not contract the disease after being exposed to live smallpox. Jenner called the procedure “vaccination” after the Latin word vaccinus, meaning “from cows” and devoted the rest of his life to educating and vaccinating the masses. 200 years later in 1980, Jenner’s innovation led to smallpox becoming the first and only infectious disease to be eradicated intentionally. Although the eradication program cost the international community $300 million, in addition to the humanitarian benefits it has led to significant economic benefits. The US Government Accounting Office (GAO) calculated that the United States had saved a net total of $17 billion in other direct and indirect costs related to vaccination, medical care, and quarantine related to smallpox. According to GAO figures, the economic benefit between 1971, when the US achieved eradication and eliminated routine vaccination, and 1988 was an average annual return of 46 percent on its global campaign investment. In our current fight against the COVID-19 pandemic, researchers around the world are racing to develop a vaccine and follow Jenner’s footsteps by eradicating COVID-19 through vaccination.

Cholera → 19th Century


A disease caused by the Vibrio Cholerae bacterium that spreads through the oral-fecal route, cholera shows that epidemic diseases aren’t purely random, but rather exploit features of society that are social, economic, political and environmental. Since cholera spread through the oral-fecal route, it thrived on such features of early industrial development in the 19th century such as chaotic and unplanned urbanization, rapid demographic growth, crowded slums with inadequate and insecure water supplies, substandard housing, an inadequate diet, ubiquitous filth and the absence of sewers.

Cholera was the most dreaded disease in the 19th century because of its sudden appearance and the speed of its course through the human body. Apparently, robust and healthy people would finish lunch and die in agony before dinner or board a train and perish before reaching their destination as a result of cholera. Moreover, the gruesome symptoms of the disease that made patients explosively lose fluids and die instantly has led to a much more sparse presence of cholera in the arts compared to the plague and smallpox.

Furthermore, unlike smallpox and even the plague, cholera’s mode of transmission via the oral-fecal route marked it as a classic example of a “social disease,” with a preference for inflicting the poor in environments with substandard housing, insecure water supplies, congestion, unwashed hands, malnutrition and societal neglect. The Italian city of Naples, which was compartmentalized into a lower and upper city in the early 19th century clearly reveals this phenomenon. While the death rate in all of Naples in 1837 was 8 per thousand people, the lower city, which was home to the poor, had a much higher death rate of 30.6 per thousand people. This was mainly because of the poor hygiene, poverty, low access to clean water, and high unemployment in the lower city of Naples. In fact, the lower city had an unemployment rate of 40% at the time, and an average room in one of its crowded tenements occupied approximately seven people.

Cholera’s unequal preference for the poor not only in Naples, but throughout the world in turn led to social instability and class tensions that were fuelled by conspiracy theories about a diabolical plot to destroy the poor. These tensions were further exacerbated by the draconian measures taken by public health officials to reduce the spread of the virus through sanitation. As a result of an increasing lack of trust among the poor, people stopped reporting cases of cholera and resisted intervention from physicians. In some cases, the tensions evolved into physical violence and full scale riots at major cholera hospitals that injured many doctors and health workers.

Just like with every other major outbreak since the plague, at the onset of the cholera outbreak public health officials turned to draconian anti-plague measures that were often imposed with military power. However, these measures proved to be counterproductive as they led to mass migration that further increased the spread of cholera, and increased social disorder that further devastated economies. Therefore, the most important public health response against cholera was the sanitation movement that was theorized in the 1830s and progressively implemented until World War I. The sanitation movement’s first objective was to undo the rapid urbanization caused by the industrial revolution that had led to increased population density and ubiquitous filth in major cities. In Naples for example, the government began their urban re-planning efforts by destroying the overcrowded tenements in the lower city and using the rubble to raise its level. The sanitation movement also established a clean water supply, and a comprehensive sewage and drainage system in order to increase hygiene and reduce the spread of bacteria.

Although the sanitation movement has largely contained cholera, the disease still remains at large in developing countries that have high population densities and absolute levels of poverty just like the lower city of Naples did in the 19th century. However, the modern version of the disease is caused by the bacterium Vibrio El Tor, which is a mutated version of the original Vibrio Cholerae. This change was caused by natural selection because Vibrio cholerae was too lethal to be successful biologically since its hosts would die off too soon for the microbe to infect more people. As a result, modern cholera is far less virulent but more likely to induce epidemics since many remain asymptomatic after they are infected.

Spanish Influenza → 20th Century


In addition to being the last major pandemic we faced, Spanish Influenza or the Spanish Flu is often compared with COVID-19 because of the many similarities between the two pandemics. The Spanish Flu came about when a strain of bird flu and human flu came together in a pig on a farm in Kansas, and then mutated enough to cross the species barrier once again to humans. Since this virus was created through transmission between different species like with COVID-19, it is called a zoonotic virus. Although the virus came together in Kansas, it’s called the “Spanish Flu” because the Spanish press were the first to report on the disease since they were neutral during World War I. After being spread via droplets and fomites, the virus that causes the Spanish Flu gets embedded deep in the lungs causing a rapid immune response that leads to the production of white blood cells and fluids within the lungs suffocates the patient by limiting breathing space.

Once the outbreak began in the Spring of 1918, it spread across the world because of WWI and eventually led to between fifty and a hundred million deaths worldwide, which far outweighs the eighteen million deaths caused by WWI. In fact, the Spanish Flu killed more people in the first 25 weeks since the initial outbreak than HIV has killed in the last 25 years. The pandemic also had a major impact on the war-time economy at the time because it disproportionately affected people between the ages of twenty and forty, who make up much of the world’s total labor force. Although the initial outbreak was contained, there was a second wave of the disease in Autumn of 1918, which featured a more deadly version of the disease that often led to death within a few hours or days. Thereafter, there was a final wave with intermediate severity between the first and second waves in the early months of 1919. Eventually, the pandemic ended around 1920 and by 1957, the virus disappeared after evolving to lose its virulence.

Since the nature of the disease is very similar to COVID-19, the public health strategies imposed to contain the outbreak during the pandemic are also very similar to those used today. Hand washing and coughing into elbows were encouraged; everyone was forced to wear masks; and lockdowns and social distancing were the norm. In fact, events from the Spanish Flu in 1918 reveal how important social distancing can be when dealing with a pandemic. Both Philadelphia and St. Louis in the US detected their first case of the Spanish Flu in mid September of 1918. However, while St. Louis imposed strict social distancing measures thereafter, Philadelphia hosted a parade with 200,000 people in attendance just ten days later. As a result, as seen in the figure below, Philadelphia failed to “flatten its curve” and suffered a much higher death rate compared to St. Louis. Furthermore, although social distancing measures stayed in effect for longer in St. Louis, the city managed to achieve much higher levels of long run economic growth post-pandemic because its labor force remained healthy compared to cities like Philadelphia that didn’t enforce strict social distancing and in turn paid the price.


In addition to the aforementioned containment strategies during the pandemic, the Spanish Flu led to more long term implications on public health after the disease had panned out. Since the Spanish Flu disproportionately affected the poor, the international community moved away from eugenics to the idea of “socialized medicine” and implemented national healthcare systems that provided healthcare for all after the pandemic. The Spanish Flu also led to increased funding for healthcare, and research into epidemiology; by 1925 all US states were actively using a national disease reporting system that would allow authorities to act fast when an outbreak took place. A predecessor to the WHO called “The International Bureau for Fighting Epidemics” was also founded in 1919 to identify and contain epidemics that take place internationally.

SARS → A Dress Rehearsal for the 21st Century


Severe Acute Respiratory Syndrome or SARS was the first deadly infectious disease caused by a Coronavirus that originated in Guangdong, China in November 2002. In fact, the Coronavirus that caused SARS shares 70% of the genetic material with the Coronavirus that causes COVID-19. Although SARS also spreads via droplets and fomites like COVID-19, it was less contagious and more fatal with a case fatality rate of 10%. SARS was classified as an international health threat in March 2003 by the WHO, and later contained by July 5th 2003. Between the first case in November 2002 and July 5th 2003, 8098 cases were reported, 774 died and Asian countries alone suffered an economic loss of over $60 billion as a result of SARS. SARS also happened to be the first major disease to spread via air travel; the disease spread very quickly from China to Hong Kong, Taiwan, Singapore and Toronto.

The public health strategies employed to contain the disease happened to be the very same strategies that were developed to fight the plague in the 14th century and are widely used to fight COVID-19 today. However, the virus was not contained as a result of an exemplary response but rather mostly because of serendipity. The virus that caused SARS disappeared because it was too fatal and not contagious enough to survive. Research suggests that unlike COVID-19, SARS was only contagious when the virus was deeply embedded in the patient’s lungs. However, by this point the patient was unlikely to spread the virus since he/she would have already started showing symptoms and been put in isolation. As a result of the high fatality rate and lack of contagiousness, SARS eventually ran out of hosts and disappeared.

SARS was akin to a dress rehearsal in the sense that it revealed many key weaknesses in the world’s pandemic response system and raised many alarms without causing much damage. The disease spread much more than it should have due to a Chinese policy of concealment enforced between November 2002 and March 2003 as a result of the Communist party’s fears that the impoverished living standards, inadequate health care system and lack of preparedness for a health crisis within China would be exposed to the world. Moreover, by bringing developed regions with ample healthcare resources like Hong Kong, Singapore and Toronto to its knees, SARS exposed the absence of surge capacity within healthcare systems and foreshadowed the ensuing catastrophe if a pandemic were to strike a LEDC. Although SARS gave us hints that we couldn’t ignore, many of the questions it raised remained unanswered and we’re paying for this complacency with the devastation we are seeing today during the final performance that is COVID-19.


Although the war between microbes and humanity has been a long and arduous one throughout our life on earth, each of these pandemics no matter how bad the suffering has led to innovation and positive change thereafter. This, together with the fact that we have prevailed every time thus far and have never been more ready for a pandemic in terms of science and technology gives us an opportunity to be optimistic and have some hope in the current battle against the COVID-19 pandemic.

However, studying the pandemics of the past also reveal that infectious diseases are caused by poor economic decision making and the negative externalities prevalent in free markets. The risk of further pandemics will only increase if we continue to tolerate wet markets, inequality, poverty, deforestation, and the countless other negative externalities that make society vulnerable to infectious diseases. Therefore, moving forward public health must be prioritised and our economic and political systems and decision making will have to reflect this reprioritization to minimize the risk of future pandemics.

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