If you're asking what century was the plague, you're probably thinking of the 14th century. That’s the big one. The Black Death. It’s the period between 1347 and 1351 that everyone learns about in school, where basically a third of Europe's population just vanished in a few years. But history is actually messier than that. The plague isn’t a one-hit-wonder. It’s more like a recurring nightmare that popped up across several centuries, and honestly, the "century" it happened in depends entirely on which pandemic you're talking about.
Plague isn't just an old-timey word for "lots of people dying." It’s a specific disease caused by the bacterium Yersinia pestis. Scientists like Monica Green and others who study paleogenetics have found that this stuff has been messing with humans for way longer than we thought. We’re talking thousands of years. But in terms of the "Big Three" pandemics that shaped the world, we have to look at the 6th, 14th, and 19th centuries.
The 14th Century: The One Everyone Remembers
The mid-1300s were absolute chaos. This is the what century was the plague answer most people are looking for. Around 1347, the Black Death arrived in the Mediterranean via merchant ships coming from the Black Sea. Legend (and some chroniclers like Gabriele de' Mussi) says it was used as biological warfare during the siege of Caffa, where bodies were supposedly catapulted over city walls. Whether that’s 100% literal or a bit of medieval flair, the result was the same. People started dying. Fast.
It wasn't just a "bad flu" year. In places like Florence or London, the social fabric just ripped apart. Boccaccio wrote about it in the Decameron, describing how neighbors avoided neighbors and even parents abandoned their children because they were so terrified. The 14th century became defined by this event. It fundamentally shifted the economy because there weren't enough peasants left to work the land, which basically killed off feudalism. Laborers could suddenly demand higher wages because, well, they were the only ones left alive to do the work.
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Why 1347 wasn't the end of it
People often think it hit in the 1300s and then just went away. Nope. It stuck around for another 400 years in what historians call the Second Pandemic. It would flare up every ten or twenty years in different cities. You had the Great Plague of London in the 17th century (1665), which killed about 100,000 people. Then you had the Great Plague of Marseille in 1720. The 14th century was just the grand opening of a very long, very dark era.
The 6th Century: The Forgotten First Wave
Before the Black Death, there was the Plague of Justinian. This hit in the 6th century, specifically starting around 541 AD. It’s named after the Byzantine Emperor Justinian I, who actually caught the plague himself but somehow survived. Most people didn't.
Procopius, a historian from that time, claimed that at its peak, 10,000 people were dying every day in Constantinople. Modern historians think that number might be a bit of an exaggeration, but the impact was still massive. It weakened the Byzantine Empire right when Justinian was trying to reunite the Roman world. If you want to know what century was the plague first officially recorded as a global pandemic, this is it. It lingered in waves until about 750 AD. Then, weirdly, it just kind of disappeared for 600 years until the 14th-century outbreak.
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The 19th Century: The Modern Plague
Most people are shocked to find out there was a third pandemic that started in the 19th century. This one kicked off in the 1850s in Yunnan, China. It eventually hit Hong Kong and Guangzhou in the 1890s and then hitched a ride on steamships to the rest of the world. It reached Hawaii, San Francisco, and Australia.
This 19th-century version is actually the most important for science. Why? Because it’s when we finally figured out what was actually happening. In 1894, a physician named Alexandre Yersin identified the bacterium (Yersinia pestis) in Hong Kong. Around the same time, Shibasaburo Kitasato was also working on it. Before this, people thought "miasma" or bad air caused it. Or they blamed the alignment of the planets. Finally, in the late 1800s, we realized it was fleas on rats.
It’s still here, sort of
Technically, that third pandemic didn't "end" until 1960 according to the World Health Organization. Even now, we see cases in the 21st century. In the American Southwest, rural Madagascar, and parts of the Democratic Republic of the Congo, the plague still exists in rodent populations. We have antibiotics like streptomycin or gentamicin now, so it’s not the death sentence it was in the 14th century, but it's a reminder that biology doesn't care about our calendars.
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What Most People Get Wrong About the Century of Plague
We have this mental image of the Middle Ages being one long, continuous plague. That’s not quite right. There were long stretches of time where things were actually okay. The "Plague Century" (the 14th) was unique because of the speed of the spread.
- The Rat Myth: We always blame the black rat (Rattus rattus). But some recent studies, like those from the University of Oslo, suggest that human ectoparasites—like body lice and human fleas—might have been the real culprits for how fast it moved through cities.
- The "Bring Out Your Dead" Trope: While things were grim, medieval people weren't just helpless. They tried to implement quarantines. The word "quarantine" comes from the Italian quaranta giorni, meaning 40 days, which was how long ships had to wait off the coast of Venice during the 14th century to prove they weren't carrying the disease.
- Climate Change: There’s a lot of evidence that the transition from the Medieval Warm Period to the Little Ice Age played a role. Cooler, wetter weather in the 14th century led to crop failures, which meant people were malnourished and had weaker immune systems when the plague arrived.
Why Knowing the Century Matters Today
Understanding what century was the plague helps us see patterns in how humans react to crisis. Whether it’s the 6th, 14th, or 19th century, the playbook is usually the same: fear, followed by scapegoating, then eventually, social change. The 14th-century plague led to the Renaissance in a roundabout way by breaking old social hierarchies. The 19th-century plague led to modern urban planning and better sanitation laws.
Honestly, the plague is less of a "when" and more of a "whenever the conditions are right." It’s a biological reality that we’ve finally managed to cage with modern medicine, but the history of it is etched into our DNA—literally. Some researchers believe that the survivors of the 14th-century plague passed down certain immune system genes that still affect how we respond to diseases today.
Actionable Steps for History Buffs and Travelers
If you’re fascinated by this history or traveling to areas where plague history is prominent, here’s how to engage with it responsibly:
- Visit the "Plague Villages": If you’re in the UK, go to Eyam in Derbyshire. In 1665, the villagers heroically quarantined themselves to stop the plague from spreading to nearby Sheffield. It’s a powerful, sobering place.
- Check the CDC Maps: If you’re hiking in the Western US (like Colorado or New Mexico), don’t feed the prairie dogs. They can still carry the plague. It sounds like a joke, but it's real. Just keep your distance.
- Read the Primary Sources: Skip the Hollywood versions. Read Samuel Pepys’s diary for a first-hand account of the 17th-century plague in London. It’s way more relatable than you’d think—he talks about the fear, the gossip, and the weird remedies people tried.
- Support Public Health: The lesson of the 19th-century pandemic was that surveillance and rapid response save millions of lives. Supporting global health initiatives keeps these "old" diseases in the history books rather than the news.
The plague wasn't just a 14th-century event. It was a 6th-century collapse, a 17th-century local disaster, and a 19th-century scientific breakthrough. It’s a long, recurring story of human survival against a very tiny, very persistent enemy.