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From The Black Death To Spanish Flu And Smallpox, A Brief History Of Plagues

No matter where you look up the meaning of the word "plague", it's never a good thing. It can be confusing, because as a verb, plague means "to cause continual distress", yet as a noun, it means a deadly disease that spreads very quickly – what we would today call a "pandemic". It can also refer to one specific disease, Yersinia pestis. 

On top of that, a plague can refer to a large number of insects or animals in one place that are causing a lot of damage, like the locusts currently swarming in east Africa. 

In this article, we'll talk about the plagues, or pandemics, that humans have battled with throughout history. 

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Black Death

The worst plague in history was the Black Death, which may have killed up to 200 million people. This was caused by a bacteria, Yersinia pestis, that first hit Europe in the 1340s. 

People still disagree over where it came from, but the most common theory is that it first emerged in Asia, in a certain type of flea that lived on rats. In fact, when scientists in the 1900s were looking for the cause of a similar disease, they came to Hong Kong as part of their investigation. 

Back in the 1300s, life was pretty dirty, as people didn't know anything about hygiene. They also didn't have much medical knowledge – they had never heard of antibiotics or quarantine. This meant that the plague killed around 90 per cent of the people it infected, and in some cases, it killed everyone it infected. But this didn't wipe it out.

Several waves of the Black Death swept the globe and killed hundreds of millions of people.

Photo: Shutterstock

Two more deadly waves of the plague hit in the 1500s and 1800s. In fact, scientists think that it may have been around before the 1300s, as there are records of a similar disease in Rome in 146AD, known as the Justinian plague.

The symptoms of the plague were awful. It started with a swelling in the lymph nodes under the armpit or in the groin, until they were about the size of an apple. Once the swellings burst, people had a fever, vomited blood, and soon died.

Spanish flu

After the devastation of the first world war came the Spanish flu. It did not actually come from Spain, but this was where it first became bad enough to be noticed. It killed up to 40 million people – more than all the deaths of the first world war. It spread across the world, aided by the movement of  hundreds of thousands of soldiers to far-off battlefields. 

It started out like a normal cold, so people were not too worried about it. But then those who were infected developed pneumonia, a lung condition which makes breathing difficult. After that, victims eventually suffocated. 

No one knows where the Spanish flu started, but recent studies show that the virus may have emerged when strains of pig and human flu infected the same host, and their genes combined to create a new mutation. 

Medical workers wore masks to avoid the Spanish flu at a US Army hospital in 1918.

Photo: Shutterstock

Smallpox 

There is no doubt that plagues changed the course of history. They caused empires to fall and new ones to arise. Smallpox first emerged around 68,000 years ago. We have no idea how many people it has killed, but we do that in the 20th century alone it killed around 500 million people. 

Smallpox was introduced to the Americas by European colonisers in the 1400s. It was responsible for the fall of the Aztec and Incan empires, and killed up to 90 per cent of the Northern Native American population – allowing the Europeans to steal the land and claim it as their own.

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Smallpox was the leading cause of death in the 18th century. And, like all good plagues, it was awful, causing sufferers to break out in small blisters all over their bodies that caused them great pain.

People did notice, however, that once someone had survived smallpox, they never got it again. So, in the 10th century, people in China began taking some pus from the infected blisters and scratching it into their own skin. This allowed the body to learn the virus' code and build immunity to defeat it. In 1798, an British doctor, Edward Jenner, developed a vaccine. In 1966, the World Health Organisation began a global vaccination campaign to wipe out smallpox for good. The last-ever case was diagnosed in 1977. Smallpox is one of only two infectious diseases to have been completely stopped. Hooray for vaccines!

Why Does Plague Keep Plaguing Humans?

Throughout human history, different infectious diseases have taken the mantle of "most deadly disease" infecting humans. In the past century alone, the human population has experienced many pandemics: COVID, HIV and various influenza outbreaks – to name a few. Some have lasted for centuries and persist today, such as tuberculosis. Others are often thought of as being consigned to the history books.

Before the 20th century, the most-deadly-disease mantle was held in Europe and surrounding areas by the bubonic plague. Three major pandemics of this disease have occurred in the past 1,500 years. The first occurred from the fifth to the seventh century, killing about 15 million people in the Mediterranean basin, and heavily affecting the Byzantine, Sasanian and Roman empires.

A much larger second outbreak, called the Black Death, then occurred in 14th-century Europe, where over 50 million people, around 50% of the entire European population, died from this disease.

The third wave of this pandemic then occurred globally in the 19th and 20th centuries, killing a further 30 million people worldwide, many of these in China and India.

However, from the 1960s onwards, cases dropped dramatically, and the bubonic plague is not often considered a modern disease. Despite this, a new case was recently reported in the US, renewing interest in this disease.

Although no longer common in many parts of the world, the bubonic plague still exists in geographic pockets and can spread in communities if the right mix of conditions are present.

An engraving showing a passerby offering water to a man dying of plague during the Great Plague of London. Classic Image/Alamy Stock Photo

The bubonic plague, or plague for short, is caused by a bacterium called Yersinia pestis. There are three types of plague caused by this pathogen, each with a different part of the body as the main site of infection: pneumonic is mainly lung-based, septicemic is mainly blood-based, and bubonic is mostly in the lymph nodes.

Although one form can turn into another during an infection, generally which form a person has is driven by how they were infected.

Bubonic plague is the form of Y pestis infection that is spread by fleas that live on small animals, mostly rodents such as the house and field rat. These rodents serve as reservoirs for the bacteria: they show little-to-no symptoms but can pass the bacteria to others, including humans.

This transmission from rodents to humans takes place via fleas. These insects bite the rats and afterwards may jump and bite a human, injecting the plague bacterium into the lymphatic system of the human. The bacteria then travel through this system to the lymph nodes and infection begins.

The main symptom of bubonic plague is swollen lymph nodes, usually in the neck, groin, thighs and armpits. These swollen nodes, called buboes, can cause the tissue around them to turn black and die. They may also burst open, releasing the pus inside.

A plague patient showing their buboes. Gado Images / Alamy Stock Photo

Other symptoms include fever, headaches and vomiting, and the pathogen may spread to other parts of the body, such as the lungs and blood, causing other forms of the plague. Bubonic plague kills 30-60% of people, whereas pneumonic and septicaemic are always fatal if left untreated.

So why was this so prominent hundreds of years ago but barely heard of today? It is all about having that crucial combination of vector (flea), reservoir (rodent) and bacteria (Y pestis) all occurring together and in close contact with humans.

Before the 19th century, people primarily thought that disease was spread by miasmas: noxious forms of air. It was only after the 1880s that people realised that microscopic organisms transmitted between humans, animals and the environment can cause diseases.

From this, sanitation improved in many parts of the world, separating rodents from humans and breaking the cycle of plague transmission. The invention of antibiotics, especially fluoroquinolones from the 1960s onwards, further drove down the cases of plague as proper treatment could now be given for all forms.

Today, we still see cases of plague in specific hotspots, mainly in Asia, Africa and South America. The Democratic Republic of Congo, Peru and Madagascar are the countries with the most cases.

Madagascar alone has dozens of cases a year, with more major outbreaks occurring in 2014 and 2017 (the latter had over 2,000 cases). The dense forest areas are home to many rodents, and contact between people and these ecosystems is the cause of these modern outbreaks.

The plague will probably never be eradicated. Because of its complex transmission network of fleas, rodents and humans, it is nearly impossible to find, control and treat all these aspects. However, through proper handling of animals, separation of natural reservoirs and humans, and quick and effective treatment, the number of plague cases is decreasing every year, with hopes of negligible case numbers in sight.

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