5 Pandemics that Shaped the World

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5 Pandemics that Shaped the World

By Ally Hughes

Before we start exploring some of the pandemics of the past, I think it is important to clarify some terms that you have all heard of by now, but have specific meanings in a scientific context.

Way, way back in 2019, reports began to appear of an OUTBREAK of a particular type of coronavirus in Wuhan, China. An outbreak in this context, is a when an unexpectedly large number of people became infected and as numbers continued to increase, the outbreak progressed to an EPIDEMIC where a large number of the population in Wuhan became infected. Epidemics are always localized to a region or a country. It is only when the disease begins to spread more widely that it is classified as a PANDEMIC. A way to remember this is that a pandemic has a passport and so travels across boundaries. An excellent infographic on pandemics and their causes can be found here.

Our current pandemic, COVID-19, is caused by a novel coronavirus named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and is now present on all continents except Antarctica. But I’m sure you’re sick of hearing about this pandemic, so let me tell you about some others that have had an unforgettable impact on our world.

1.      The Plague of Justinian (541-542)

Type: Bacteria, Yersinia pestis

Death toll: 30-50 million people

In 527 AD, Justinian the Great became leader of the Roman Empire and set about the “restoration of the Empire.” Under his power, the Roman Empire secured western European territories, conquered the Vandal Kingdom in North Africa, and even subdued the rebel Tzani people that lived along the Black Sea.

His ambitious plans were coming together as he peered out across the Empire capital of Constantinople. However, in 541 AD, news began to spread of a disease that had travelled from Egypt through rats and transport of grain and it rapidly began decimating the population.

What had started as an epidemic in Egypt had now began to spread throughout the Roman Empire, becoming a pandemic. An historian of the time, Procopius, reported 10,000 deaths per day in Constantinople and that the city smelled like the dead. This plague, which is the first recorded, has long been credited with being hugely influential in the fall of the Roman Empire. This has recently been disputed with evidence that this pandemic was far less consequential in the fall of the Empire.

It actually wasn’t until 2014 that scientists had concrete evidence that the Plague of Justinian was caused by Yersinia pestis, when researchers isolated DNA from the teeth of two individuals from this period found in Aschheim, Germany. In 2016, another scientific article reported a high-quality full genome sequence of Yersinia pestis from another individual from the 6th century in Altenerding.

2.     Black Death/Bubonic Plague (1347-1351)

Type: Bacteria, Yersinia pestis

Death toll: 200 million people

By the end of the 13th Century, Medieval Europe was really thriving. A warm period is climate let to fruitful harvests and the population was booming. However, they had little idea of what the 14th Century would hold.

The early 1300s brought some of the worst weather they had experienced and with it the failing of crops and poor harvests. The Great Famines that ravaged Europe in subsequent years, causing millions of deaths. As if this wasn’t enough, our nemesis from Roman times, Yersinia pestis, was being harboured by fleas and transported along the silk road from Asia to Crimea. Soon the Bubonic Plague or Black Death was devastating populations and is still known as the deadliest pandemic in history after wiping out 30-60% of the European population. It took over 100 years for the population to recover after the horrific first-half to the 14th Century.

The bubonic plague is one of three types of plague caused by Yersinia pestis, alongside scepticemic and pneumonic plagues. Because the bacterium is transmitted through flea bites on the skin, the infection takes place primarily in lymph nodes causing them to swell and discolour – as suggested by the name Black Death. And although we often consider the plague a thing of the past, the bacterium can survive for long periods of times in rodent hosts which occasionally leads to epidemics around the world.

3.      Smallpox (1520 onwards)

Type: Virus, Variola major virus

Death toll: 56 million people

Lady Mary Wortley Montagu, and English aristocrat and wife of the ambassador of the Ottoman Empire, often accompanied her husband to Constantinople. It was here that she first heard of the practice of variolation, a method to protect people from Smallpox.

Smallpox was a disease caused by the Variola major and minor viruses that had caused devastating epidemics across the world from the early 16th Century and killing 400,000 Europeans a year by the 18th Century. To prevent contraction of Smallpox, scabs that had been removed from patients with mild symptoms were ground up and administered nasally. This would lead to a small non-fatal infection and lifelong immunity to the disease. It is thanks to her that this practice became widespread in Britain after an outbreak of the disease in 1713.

In the 1760s, Edward Jenner was studying medicine in Gloucestershire and made a connection between smallpox and another viral disease, cowpox. His research led him to perform a type of variolation where he applied scabs from a cowpox patient over a scratch on a healthy patient’s arm. James Phipps, the young subject of this experiment, was the first person to gain immunity from smallpox without actually being infected by the causing virus.

Thanks to this incredibly unethical work, we now have vaccines (with “vacca” coming from the Latin word for “cow”) and have successfully eradicated smallpox from history. It is one of two infectious diseases that have been eradicated, the other being rinderpest.

4.      Cholera (1817-1923)

Type: Bacteria, Vibrio cholera

Death toll: 38 million people

The 19th and early-20th Century saw six major Cholera outbreaks caused by the bacterium Vibrio cholera. The first pandemic originated in India with pilgrims heading to and from Calcutta (modern day Kolkata) believed to be responsible for the spread of the disease into other parts of Asia, whilst British troops occupying India at the time are believed to have brought the disease to Britain and other parts of Europe. Each of the six pandemics actually comprised several epidemics across the world and often led to spikes in racism and discrimination as people claimed the disease came from immigrants traveling from poor countries. Outbreaks of cholera still regularly occur in some underdeveloped countries as access to clean water is limited.

In 1854, and outbreak of cholera in London caught the attention of John Snow who observed that only people collecting their water supply from the pump on Broad Street were becoming infected. He postulated that people became infected by drinking the contaminated water. To prove his theory, he created a double-blind study, a method that is still used in medical and scientific practices today to eliminate biases in observations. He is also credited as founding epidemiology, a field of science that studies patterns of distribution and associated factors of diseases – for example the track and trace methods being used to contain COVID19 in some countries.

5.     HIV/AIDS (1981-PRESENT)

Type: Virus, Human immunodeficiency viruses

Death toll: 25-35 million people

It is believed that the Human Immunodeficiency Virus (HIV-1), the virus that causes the disease Acquired Immune Deficiency Syndrome (AIDS) first originated from a virus found in primates that was likely contracted by hunters in Africa. And the story from here is utterly horrifying and fascinating. And despite what the media in the 1980s would have us believe; sexual transmission is 10-fold less efficient than transmission through infected syringes.

The start of the 20th Century saw massive spread of disease across the Belgian Congo (now the Democratic Republic of Congo). Sleeping sickness, smallpox, amoebic dysentery, venereal diseases, and swine flu were all likely imported to the colony through European colonists and Asian traders. In order to preserve their labour force, and protect the white colonists living in the area, the Congo Free State (led by King Leopold II of Belgium) rolled out massive disease-management programmes in Congo and the establishment of the Institute of Tropical Medicine in Belgium. It is estimated that some Congolese received up to 300 shots in a lifetime. These campaigns lead to one of the best healthcare infrastructures in Africa at the time and a huge reduction in deaths from sleeping sickness. However, glass syringes were re-used and often not sterilised correctly due to constant electricity faults, allowing the spread of HIV among the Congolese population and beyond.

After WWII the white Europeans occupying the Congo fled the continent, leaving behind few qualified to lead a nation in turmoil. The UN sent Haitian volunteers to continue basic education and medical campaigns in Congo. It is through dodgy plasma centers in Haiti, as well as it being a destination for homosexual American tourists, that carried the disease to the United States. The pandemic in the US was rarely treated as a public health crisis, but rather as a political and religious tool that led to discrimination and brutality against the LGBTQ+ community that is still rampant today.

An excellent book by Dr. Jacques Pépin, “The Origins of AIDS” (reviewed here in the NY Times) showcases how complicated epidemiology studies can be and that scientists must always remain open-minded and inquisitive. But the ongoing AIDS pandemic also highlights how politics and religion can adversely affect and even hinder attempts to address public health crises through scientific and medical knowledge.

FEMS Microbiology