6 Diseases That Have Shaped Human History
6 diseases that have shaped human history infectious diseases have had some pretty major impacts on human history, and that’s putting it mildly. Take the Black Death of the Middle Ages, which wiped out more than a third of the population of Europe, or smallpox, which hitched a ride to the Americas on ships and decimated Native Peoples. We’ve been haunted by microbial enemies, but sometimes our drive to understand them has laid the foundations of modern science. So here are six of history’s most devastating diseases and how they affected us in some pretty big ways. We’ll start our list with the plague caused by the bacteria.
Yersinia pestis. It’s transmitted to people when they’re bitten by fleas carried by rodents. Most famous for the fourteenth-century outbreak called the Black Death plague. Bacteria actually caused three different forms of the disease. You’ve probably heard of the most common one, bubonic plague.
It’s when these bacteria target the lymphatic system, which helps protect your body from junk-like toxins. Between two and 6 days later, infected victims get a high fever, headaches, and vomiting. Plus, they get swollen lymph nodes called Bobos, which give the plague its name. Bubonic plague causes plenty of damage on its own, but if it’s left on and treated, it can develop into another form, though these kinds can also occur on their own. If the bacteria, in fact, the bloodstream, it’s called septicemia plague.
They can cause clots that keep blood from reaching tissues, which turn black as they die, or if the microbes, in fact, the lungs. It’s called the mnemonic plague. This can lead to bloody coughs and rapid death unless people transmit the plague through tiny droplets in the air. Today, all forms of plague can be treated using antibiotics, but they kill half or more infected patients, which had some huge effects on society. The first confirmed plague epidemic as it’s called the Justinian Plague.
It swept through the Roman Empire starting in 5 41 Ce and contributed to its fall in the Roman capital of Constantinople. It’s estimated that upwards of 5 0 people per day were killed at its peak. The second big wave reached Europe in 13 47 when merchant ships arrived in Italy full of six sailors. The Black Death swept through the continent in just a few years, and during that time, it’s estimated that a quarter to half of all Europeans died some 25,000,000 people. Over the next couple of centuries, the plague kept cropping up, and the first quarantines were implemented.
At the time, it was thought that infectious diseases were transmitted by bad air. So officials tried to isolate sick people and those traveling from places with an outbreak to prevent more deaths. And even though the science was wrong, quarantines helped prevent the spread of mnemonic plague between people and controlled the rats with fleas that carried plague bacteria. The last huge wave of outbreaks began in 18 94 in rural China, sweeping through Asia and Australia. And finally, after a few decades, scientists discovered the bacteria and carriers behind it all, which led us starts squashing out this disease.
Smallpox was also a major cause of death in the past and killed nearly 30% of all people who had it. It’s a disease caused by the variola virus, which starts with a high fever and headache. Then small bumps full of infectious fluid appear all over. Those are the pox and in survivors. They eventually scab and turn into scars.
Humans infected each other through tiny droplets, coughed, or sneezed through the air. But in a Super gross twist, the pox fluids and crusty scabs got all over clothes and blankets and could infect new hosts, too. Smallpox was devastating for lots of human history, but it hit especially hard when colonists from Europe invaded the Americas. The native populations had immune systems that were adapted to fight off local diseases, not foreign ones. So the variola virus-infected and killed huge numbers of them.
Overall, diseases like smallpox may have caused the death of up to 90% of the Native American population. Smallpox likely helped the Spanish conquer the Aztec Empire, too, though it’s not nearly on the same scale. The European colonists were also hurt by the disease. Some estimates think that George Washington lost more troops to the smallpox epidemic of 17 75 to 17 82. Then in battle during the Revolutionary War, casualty rates got a little better after an Army-wide variation or intentionally infecting people with a bit of gunk from a patient’s scabs to hopefully help them build immunity.
Exposing people to the virus in a controlled way ended up being safer than normal, but they still suffered from some symptoms, and there was a risk of death later. Doctors tried to make it less dangerous by using people or animals infected with cowpox, a less harmful cousin of smallpox caused by the vaccinia virus. This process was called vaccination and led to eradicating smallpox and all the vaccines we rely on today. Speaking of diseases that crossed oceans, Let’s talk about syphilis. Scientists think this sexually transmitted bacterial infection may have made its way to Europe in colonists returning from the Americas.
It’s caused by Treponema pallidum bacteria, and the initial symptoms aren’t fun. Rashes, sores, fever, headaches, and muscle pain. It’s transmitted by direct contact with the sores or passed down from an infected mother to her child. After a few weeks or months, though, the rashes and sores disappear, and the disease goes into a latent stage where it can be detected in a blood test. But it doesn’t cause any symptoms.
And in up to a third of untreated cases, the disease comes roaring back to cause dementia, dysfunction of multiple organs, lots of pain, and death. The first recorded outbreak of syphilis began in 14 95 after a victory celebration by the French Army with infected sex workers. So the people of the time started to call it the French disease, and it was pretty deadly, possibly because the disease was new to Europe and people didn’t have any immune resistance to it. It’s hard to say how many people syphilis killed because we didn’t have any medical records that tracked the cause of death, not to mention sexually transmitted infections, which were considered shameful.
So many people tried to hide them or pass them off as other things, like leprosy. What we do know is that the disease ravaged the world until one of the first antibiotics ever developed to put an end to it. Around the turn of the 20 th century, the immunologist, Dr. Paul Erlich, had discovered that certain dies only bonded to specific types of cells in his lab.
This finding led him to believe that certain compounds could target disease-causing agents like bacteria without attacking healthy tissues, a treatment that would later be called chemotherapy. Using a systematic screening process, Erlich found a chemical that he developed into an anti syphilitic drug called Silverson.
It quickly became the most prescribed drug in the world, and the process that led to its discovery earned Erlich the Nobel Prize in Physiology or Medicine 9 8 caused by a bacterium called Vibrio cholera; cholera is a severe gastrointestinal disease that causes vomiting and diarrhea as soon as 12 hours after infection.
These bacteria produce toxins that bind to small intestine enzymes that control water secretion from the rest of the body. Specifically, the toxin makes these enzymes flood the intestines with water, leading to dehydration so severe that it’s deadly. There were reports of similar-sounding diseases in India as early as 1,000 ce. But cholera didn’t become a global problem until the 19 th century when widespread trade started happening. Cholera caused a lot of fear wherever it went.
And even today, it’s a public health problem with estimated millions of cases a year. And nowadays, we know that cholera is spread through drinking water contaminated by infected poop particles. But when it hit England in the 18 thirties, medicine was ruled by the idea that disease, whether it’s black plague or cholera, was caused by bad air from corpses, in pure people, or even from swamps. So in 18 54, when a doctor named John Snow traced almost every victim of a cholera outbreak in London to a single water pump, nobody really believed him.
Town officials removed the pump’s handle, which kept people from drinking that water to humor him. In new cases of cholera dropped off sharply. But people still didn’t buy his ideas until a local Minister set out to prove him wrong. And that failed spectacularly. His report actually ended up tracing the outbreak to a dirty diaper from a baby who had contracted cholera outside of London. Doctor Snow’s revolutionary methods to track infection patterns and find the source of an outbreak is why he’s considered one of the fathers of modern epidemiology.
So it turns out this John Snow might have known something. After all, mosquitoes are a well-known pest when it comes to spreading disease, and yellow fever is no, except it’s a viral infection, and most people infected with slave virus experienced symptoms like fever, chills, aches, fatigue, and vomiting. An unlucky 15% or so of patients have it much worse with bleeding, Jandice, and multiorgan failure, leading to death.
Today we have a vaccine for yellow fever, but that wasn’t the case. In the 18 Eighties, when the French started building the Panama Canal, we knew that yellow fever was a thing, but not how it was transmitted, so we couldn’t stop people from getting sick.
More than 20 0 workers died of either yellow fever or malaria, a fun combination of both. So the French quit construction in 18 89. It wasn’t until the 900 that we discovered mosquitoes were the culprit, and the Us was able to fight the disease and finished the canal. They drained pools of water near towns and houses, which is where mosquitoes lay their eggs. And they covered water that they couldn’t drain with oil films to smother the larva that had already hatched.
And they dumped pesticides everywhere else, trying to kill all the mosquitoes they could find. The last disease on our list is a bit different from the others. It’s not transmitted; it’s inherited. And that’s why it used to be called the Royal disease. Hemophilia is a disorder that makes it hard to form blood clots, causing victims to bleed out from minor wounds that would normally seal up.
Humans have 20 different proteins that help form blood clots, but hemophilia is caused by problems in just two, and both of the genes involved are on the X chromosome. Humans have 22 pairs of nonsex chromosomes, so you have two copies of each gene plus a 23 Rd pair that’s usually either Xx or XY, and you get half of your genes from each parent for a dominant trait. You need one of your two genes to express the trait, like having a widow’s peak. On the other hand, recessive traits need two copies to be expressed so people can have only one copy, not express the trait and still pass it onto their kids.
They’re called carriers. Now, recessive traits on sex chromosomes can work a little differently because they’re not necessarily identical. People who are XY don’t have a backup copy of either set of genes. So recessive diseases caused by genes on the X chromosome just get expressed. And that’s exactly what happened with hemophilia. Historically, to try and remain pure Bloods, the Royal families of Europe were notorious for incest, and two related people have a higher chance of both being carriers for the same recessive trait because they share more genes than unrelated people.