As human civilizations flourish, so do infectious diseases. Large numbers of people living near each other and animals, often poorly sanitized and malnourished, provided fertile breeding grounds for the disease. And new trade routes abroad have spread the new infections on a large scale, creating the first global pandemics.
Here’s how five of the world’s worst pandemics finally ended.
1. Justinian’s plague – there is no one left to die
Three of the deadliest pandemics in history were caused by a single bacteria, Yersinia pestis, a deadly infection otherwise known as the plague.
Justinian’s plague arrived in Constantinople, the capital of the Byzantine Empire, in 541 CE. It was transported over the Mediterranean Sea from Egypt, a recently conquered land paying homage to the Emperor Justinian in grain. Plague-infested fleas hitched a ride on black rats that nibbled on the grain.
The plague decimated Constantinople and spread like wildfire across Europe, Asia, North Africa and Arabia, killing around 30 to 50 million people, perhaps half of world population.
“People had no real understanding of how to fight it, except trying to avoid the sick,” said Thomas Mockaitis, history professor at DePaul University. “With regard to the end of the plague, the best assumption is that the majority of people in a pandemic survive in one way or another, and those who survive have immunity.”
2. The black plague – the invention of quarantine
The plague never really disappeared and when it returned 800 years later, it killed with reckless abandonment. The black plague, which struck Europe in 1347, claimed the lives of 200 million people in just four years.
As for how to stop the disease, people still had no scientific understanding of the contagion, says Mockaitis, but they knew it had something to do with proximity. This is why avant-garde officials from the Venetian-controlled port city of Ragusa have decided to keep the newly arrived sailors in solitary confinement until they can prove that they are not sick.
At first, the sailors were detained on their ships for 30 days, which became known in Venetian law as a trentino. Over time, the Venetians increased forced confinement to 40 days or quarantino, the origin of the word quarantine and the beginning of its practice in the Western world.
“It certainly had an effect,” says Mockaitis.
READ MORE: How rats and fleas spread black plague
3. The Great Plague in London – Sealing the Sick
London never really took a break after the Black Death. The plague has resurfaced about every 20 years, from 1348 to 1665—40 households in 300 years. And with each new plague epidemic, 20% of the men, women and children living in the British capital have been killed.
In the early 1500s, England imposed the first laws to separate and isolate the sick. The houses struck by the plague were marked by a hay bale attached to a pole outside. If you have infected family members, you should wear a white pole when going out in public. Cats and dogs were thought to be carriers of the disease, so there was a massive slaughter of hundreds of thousands of animals.
The Great Plague of 1665 was the last and one of the worst epidemics of several centuries, killing 100,000 Londoners in just seven months. All public entertainment was banned and the victims were forced into their homes to prevent the spread of the disease. Red crosses were painted on their doors with a call for forgiveness: “Lord, have mercy on us.”
Cruel as it was to lock the sick in their homes and bury the dead in mass graves, this was perhaps the only way to end the last great plague epidemic.
4. Smallpox – a European disease ravages the new world
Smallpox has been endemic in Europe, Asia and Arabia for centuries, a persistent threat that has killed three out of ten people infected and left the rest with marked scars. But the mortality rate in the Old World paled compared to the devastation caused to the indigenous populations of the New World when the smallpox virus arrived in the 15th century with the first European explorers.
The indigenous peoples of Mexico and the United States today had no natural immunity to smallpox and the virus cut them by the tens of millions.
“There has been no death in human history to match what has happened in the Americas – 90 to 95 percent of the indigenous population has disappeared in a century,” says Mockaitis. “Mexico goes from 11 million people before the conquest to one million.”
Centuries later, smallpox became the first viral epidemic to be stopped by a vaccine. At the end of the 18th century, a British doctor named Edward Jenner discovered that dairy women infected with a milder virus called cowpox appeared to be immune to smallpox. Jenner famously vaccinated her gardener’s 9-year-old son with smallpox and then exposed him to the smallpox virus without any harmful effects.
“[T]The annihilation of smallpox, the most terrible scourge of the human species, must be the end result of this practice “, wrote Jenner in 1801.
And he was right. It took almost two more centuries, but in 1980 the World Health Organization announced that smallpox had been completely eradicated from the face of the Earth.
5. Cholera – a victory for public health research
From the beginning to the middle of the 19th century, cholera ravaged England, killing tens of thousands of people. The prevailing scientific theory of the time stated that the disease spread through the stale air known as “miasma”. But a British doctor named John Snow suspected that the mysterious disease, which killed its victims a few days after the first symptoms, was hiding in London’s drinking water.
Snow acted as a Sherlock Holmes scientist, investigating hospital records and morgue reports to track the precise locations of fatal epidemics. He created a map of cholera deaths over 10 days and found a group of 500 fatal infections around the pump in Broad Street, a town well known for drinking water.
“As soon as I became aware of the situation and the extent of this cholera outbreak (sic), I suspected some contamination of the water from the busy street pump on Broad Street,” wrote Snow.
With strenuous effort, Snow convinced the local authorities to remove the pump handle from the Broad Street well, rendering it unusable and, as if by magic, the infections had dried up. Snow’s work did not cure cholera overnight, but it ultimately led to a global effort to improve urban sanitation and protect drinking water from contamination.
Although cholera has been largely eradicated in developed countries, it remains a persistent killer in third world countries that do not have adequate wastewater treatment and access to clean water.
READ MORE: Pandemics that have changed history
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