A history of pandemics, part 1: Disease. It's a terrifying prospect, but it has been part of human culture and of all life since the dawn of time. After all, bacteria evolved 3.5 billion years ago and viruses 1.5 billion years ago, while

we modern humans have only been around for a hundred and thirty thousand years. A myriad of infectious pathogens perpetually surround us, causing severe, mild, or even no reaction at all, depending on your health, immunity, and sometimes sheer luck. But when one of these diseases spreads rapidly, infecting

thousands, it becomes an epidemic. And when it crosses borders to infect populations in multiple countries and across continents, you have a pandemic. Epidemics and pandemics have occurred countless times in the past, infecting, injuring, and killing millions. They have

changed many lives and the course of human history in countless ways. But in the end, humanity has always continued to move forward, and in many cases, we have learned from these outbreaks to develop new techniques of treatment and prevention. Additionally, we have made massive strides forward in sanitation,

hygiene, and nutrition, making the human population healthier and less vulnerable to illness than ever before. Let's look back at some of the worst diseases and pandemics in history. Smallpox: The viruses variola major and variola minor have been hitting humanity hard in devastating waves for most of

human history. Smallpox has caused more suffering and death than any other disease. The virus is believed to have arisen in Northeast Africa about 10,000 years ago. It has been found in Egyptian mummies from 3,000 years ago, including Pharaoh

Ramses V smallpox is mentioned in medical writings from ancient India and China in the same millennium and killed at least three Chinese and two Japanese Emperors. The virus is spread through the air via the coughing and sneezing of the infected and causes fever, vomiting,

mouth sores, and fluid-filled blisters all over the body. It was fatal in about 30% of its victims, and those who survived were left scarred and disfigured by pockmarks and sometimes blinded. There are seven known religious deities dedicated specifically to

smallpox and protecting people from it, including Saponin in West Africa and Sheeta LaMotta among the Hindus. In 1022 AD, a Buddhist nun in the Szechwan region of China noticed that those who survived smallpox were never reinfected. She

ground up smallpox scabs and blew the powder up the noses of healthy people, and her unusual treatment worked. She had invented variolation, though she inoculated, died only 3% of the time, not ideal but far better than the 30%

mortality rate of the full-blown disease. Knowledge of this life-saving treatment spread very slowly and was never able to outpace the infection, which had a habit of fading out and reappearing in lethal outbreaks around the world through most of the last 3,000 years. You had about a

1 in 3 chance of contracting smallpox in your lifetime. Unfortunately, we will be hearing much more from the terrible smallpox virus as we travel through history. The Antonine plague, this scourge first appeared among Roman soldiers as they held the city of Seleucia in modern-day

Iraq under siege during the winter of 165 AD. From there it spread through the army and around the Roman Empire. Symptoms included fever, swelling of the throat, diarrhea, and skin eruptions. The underlying disease may have been smallpox or measles, both of which are

airborne and spread by coughing and sneezing. At the height of the outbreak, 2,000 people a day were dying, totaling five million people, about 25% of the Roman Empire's population. In the midst of the fear and chaos, many turned to

magic for protection. Amulets were popular and incantations were written above doorways to safeguard those who dwelt within. Among the victims was the Emperor himself, Lucius Verus. The plague was named after his co-ruler, Marcus Aurelius Antoninus, due in great part to

the ravages of the plague. Marcus Aurelius' reign marks the end of the Golden Age known as Pax Romana or Roman peace. The pestilence demoralized the population that had grown used to prosperity and stability, and the Roman Empire never fully recovered.

The plague of Justinian four centuries later, and the Roman Empire had fallen, making way for the Byzantine Empire to dominate the Mediterranean. In 541, the area was once again slammed by a devastating disease, the first recorded pandemic of the bubonic plague, which

would ravage Eurasia repeatedly for centuries. This outbreak is thought to have originated in the Tian Shan mountain ranges along the northwestern border of China. In this area, fleas carrying bacterium Yersinia pestis infected the nomadic Hun who traded with

and raided parts of the Roman and Byzantine empires. It is believed that the plague reached Egypt, where it was carried by flea-infested rats on board grain ships across the sea to Constantinople, the capital city of the Empire. Their large stores of grain were

collected and held to feed the Empire. Rats thrived in the granary, multiplying themselves and the plague, which quickly spread among the human population. Symptoms included chills, malaise, fever, muscle cramps, seizures, gangrene of the toes, fingers, lips, and nose, and the most

distinct symptom, painful lymph gland swellings called buboes in the neck, armpits, and groin. Those infected with bubonic plague had an 80% mortality rate, and death came on very quickly, within ten days of initial infection. The plague could also become airborne, causing lung

infection known as pneumonic plague, which increased the death rate to 90%. And in rare cases, the bacteria could infect the blood, becoming septicemia plague, which was fatal in almost all cases within 24 hours of contraction. 5,000 people per day died in

Constantinople, totaling 40% of the city's population. Farmers in the countryside died en masse and left their fields fallow, causing the price of grain to skyrocket and famine to ensue. And there weren't enough laborers left alive to keep the Empire running as usual. Many

blamed the plague on the Emperor Justinian, calling him a demon. He himself contracted the disease but survived. Others blamed his wife, Empress Theodora, saying this was punishment from God for her promiscuity. While probably not a demon, Justinian had overstretched

the Empire's funds with the construction of great churches including the Hagia Sophia and on wars of expansion. When the Justinian plague struck, it crippled the economy and the army, halting the growth and stability of the Empire. Justinian moved quickly to enact new

legislation to deal with the glut of inheritance cases, but he was powerless to preserve the peace. The social and economic impact of the plague was widespread throughout Europe. With the Byzantine army no longer keeping them in check, many other groups were able to

expand and conquer, including the Anglo-Saxons who first settled in the British Isles during this time. The Black Death, some eight hundred years later in the mid-1300s, the bubonic plague returned once more to decimate Europe and Asia. Climate change in Central Asia

in 1338 caused rodents to flee dried out grasslands and move into areas populated by humans where the fleas they carried spread the disease. The plague was then carried by traders along the Silk Road where it devastated every place it went. India and Mongolia were left depopulated

and the Middle East was covered in dead bodies. By 1343, the pestilence reached Crimea. There, the Mongol army had the city of Kaffa under siege when Mongol soldiers died. Their corpses were catapulted over the city walls in order

to infect the people cowering within. Genoese traders jumped in their ships to escape the war and death in Kaffa, but they unwittingly carried deadly rats with them back home to Italy. From there, the disease launched its carnage of Europe, spreading north like wildfire. The

A population already weakened by malnutrition, war, and other diseases was massacred. The Black Death is estimated to have killed around 100 million people, between 30 and 60 percent of Europe's population, making this the most deadly pandemic in history. Infection and death were so rampant that

corpses filled the streets as graveyards reached capacity and there was no one left to bury the dead. At least half of the populations of Paris and London perished. Smaller communities attempted to isolate themselves to protect against the scourge with varying degrees of

success. The word quarantine emerged in Venice, referring to the 40 days ships were required to wait in the harbor before docking to ensure that no one aboard was carrying the plague. Many turned to God to save them. In the already deeply religious era, faith

and obsession with death and the afterlife dominated culture and thought for centuries to come. The Flagellants, a group of militant pilgrims, emerged primarily in Germany and Italy. They beat and whipped themselves publicly in punishment for the sins of humanity. When the Black

Death finally abated after the better part of a decade, those who survived faced a very changed world. Peasants found there was more demand for labor than there were people to do it. They abandoned the feudal lands that their families had been enslaved to for centuries in search

of better pay, and many of them got it, becoming wealthier than ever before. This infuriated the nobles who saw themselves as inherently superior, so they imposed laws limiting everything from where peasants could live to what types of clothes they could wear. Peasants

revolted and thus began centuries of class warfare that would eventually culminate in the end of feudalism in Europe.  Koch elites, Lee, what doesn't kill you makes you stronger, and in epidemiology, this is especially true. Those who contract an infection, mild or

serious, will in most cases build an immunity to it. So if you survive and are exposed to the same pathogen again, your immune system will know how to fight back and you will likely never become ill again. Until Christopher Columbus arrived in the Americas in 1492, the people

living there had their own diseases and their own immunities to them. Their immune systems were not prepared for the onslaught of new infections carried across the sea by Europeans. In the mid 16th century, an unknown pathogen was introduced by Spanish conquistadors

which obliterated much of the population of the Aztec empire in modern-day Mexico. The viral hemorrhagic fever known as Cocoliztli was likely related to the Ebola virus. It's symptoms included a black tongue, bloody diarrhea, neurological disorders, and bleeding from

the nose, eyes, and mouth. An estimated 5 to 15 million people died, and many Aztec villages and cities were left abandoned. Spaniards saw the disproportionate infection of the Aztecs as God's punishment for their hedonism, but little

record survives as to what the Aztec people made of this horror inflicted upon them. The massive loss of life did more to make way for the Spanish conquest than swords and muskets ever could. Conquistadors took advantage and claimed much of the land left abandoned.

by the Aztec people, ensuring the downfall of their empire. Smallpox, along with other diseases, literally it was certainly not the only disease Europeans shared with the inhabitants of the Americas. Smallpox was introduced to the Caribbean island of Hispaniola in 1509 and spread to

mainland North America in the following year. Because the indigenous population had no acquired immunity, the disease wiped out thousands with an 80 to 90% mortality rate. As with the Aztecs, disease paved the way for Europeans to colonize North America and the infection

of Native Americans wasn't always accidental. In 1763, during the French and Indian War, the British army intentionally gave blankets which had touched the sores of smallpox victims to local tribe members in an act of biological warfare. But Europeans didn't

get away from smallpox scot-free. For the better part of the 18th century, it was the leading cause of death worldwide. An estimated 400,000 Europeans died each year and one in 10 infants in Northern Europe would die of

the disease before reaching their first birthday. This terrible pestilence did not discriminate between classes. It killed Queen Mary II of England, her husband King William III, and her sister Queen Anne, as well as King Louis XIV of Spain and King Louis XV

of France. George Washington survived a bout of smallpox in his early 20s, and Abraham Lincoln was in the early stages of the disease when he delivered the Gettysburg Address. Smallpox infected and scarred Holy Roman Empress Maria Theresa

and several of her 16 children, killing 4 of them. The Empress decided to have all of her children inoculated against the disease, popularizing the life-saving technique of variolation, which was first invented in ancient China. At this time, doctors would take pus from an infected

person's skin and use it to scratch the skin of a healthy person. 3% of those inoculated still died of the disease, but this was a big improvement on the 30% who died from actual smallpox. In the 1790s, English physician Edward Jenner

observed that dairymaids didn't get smallpox. He realized that this was because they had already been infected with cowpox virus, that is related but significantly less severe and almost never deadly. He tested his theory by inoculating his gardener's

eight-year-old son with pus from a cowpox sore. The boy had fever for a few days and then recovered. Jenner then inoculated him with actual smallpox and no symptoms developed. After more testing and significant skepticism and eventual acceptance by the medical community,

Jenner's new vaccination replaced the more risky variolation. After widespread vaccination campaigns throughout the 19th and 20th centuries, the World Health Organization certified smallpox, the most deadly disease in human history, as eradicated in 1979. Jenner is remembered

as the father of immunology, and basic tenants of his technique are still used today when creating new vaccines against new diseases. The world no longer has to worry about the threat of smallpox, but unfortunately there are still several more deadly diseases and pandemics to talk about, including

syphilis, cholera, the 1918 Spanish flu pandemic, and HIV/AIDS. Stay tuned for part 2 of a history of pandemics and stay safe out there. If you enjoyed this video, please like, subscribe, comment your thoughts, and check out my other history videos. 

If you really want to help, please consider supporting me on Patreon. A link is in the description. Thank you for watching. You

A History of Pandemics, Part 1

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