The short answer is they didn't. Not really. If you’re looking for a specific moment where a medieval doctor stumbled upon a magical elixir or a secret herb that wiped out the Yersinia pestis bacterium, you’re going to be disappointed. There was no "aha!" moment in 1348. People died by the millions—anywhere from 30% to 60% of Europe’s entire population—while doctors wore bird masks and stuffed their pockets with dried flowers.
It was brutal.
When we ask how did they cure the black plague, we have to look at two different timelines. There is the medieval response, which was basically a mix of prayer and panic, and then there is the modern medical reality. In the 14th century, a "cure" didn't exist because they didn't even know what they were fighting. They thought it was "miasma"—bad air—or a punishment from God, or even the alignment of the planets. It took centuries of death and the eventual birth of modern germ theory to actually "solve" the problem.
Why the Medieval Cures Were Honestly Useless
Medieval medicine was a mess. It was based on the "Four Humors," an ancient Greek idea that you stayed healthy by balancing blood, phlegm, yellow bile, and black bile. When the Black Death hit, doctors tried to balance these humors. They failed.
One of the most common "cures" was bloodletting. They’d cut you open to let the "infected" blood out. You can imagine how that went. If you’re already dehydrated and suffering from organ failure, losing a pint of blood is a death sentence. It just made people die faster. Then there was "vicary therapy." This involved taking a live chicken and rubbing its bare backside against the victim's swollen lymph nodes (buboes). The idea was that the chicken would draw out the poison.
It didn't. The chicken usually just got stressed, and the patient died anyway.
They also tried lancing the buboes. This was the most "medical" thing they did. A barber-surgeon would take a hot blade, slice open the hard, black swelling in the armpit or groin, and let the pus drain out. While this sounds disgusting, it actually gave a few people a fighting chance if they didn't die of sepsis first. But was it a cure? No. It was a localized treatment for a systemic infection.
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The Real Hero Wasn't Medicine, It Was Law
If you want to know how did they cure the black plague in terms of stopping the spread, you have to look at Venice. In 1377, the city of Ragusa (modern-day Dubrovnik) and later Venice established a trentino. This was a 30-day isolation period for arriving ships. They eventually bumped it up to 40 days, calling it a quarantena.
That’s where our word "quarantine" comes from.
It worked because the plague was biological. It needed a host. By forcing people to sit on an island or in a harbor for 40 days, the authorities were inadvertently waiting out the incubation period. If you were going to die, you died on the ship. If you lived, you were probably safe to enter the city. This wasn't a medical cure for the individual, but it was a "cure" for the community. It’s the reason the plague eventually lost its momentum.
Public health was born out of desperation. Cities started building "pesthouses" to move the sick away from the healthy. They burned the clothes of the dead. They stopped burying people in crowded churchyards and started using massive plague pits outside city walls. These weren't doctors' orders; they were administrative ones.
The Mystery of the Plague’s Disappearance
There’s this weird historical debate about why the Black Death eventually faded away. Some historians, like Ole J. Benedictow, argue that the plague didn't really leave; it just ran out of people to kill who weren't already immune.
Others point to the rats.
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The plague was carried by fleas living on black rats (Rattus rattus). These rats loved living in human houses—especially the thatched roofs of medieval cottages. Eventually, the brown rat (Rattus norvegicus) started moving in from Asia. Brown rats are more aggressive and they don't like living as close to humans. As the brown rat pushed out the black rat, the bridge between the fleas and human skin was partially broken.
Also, the climate changed. The "Little Ice Age" began, and the fleas—which thrive in warmth and humidity—didn't do so well in the cold. It was a combination of social distancing, better housing (moving from wood and thatch to brick and stone), and a literal change in the weather.
How We Actually Cure It Today
Fast forward to the late 1800s. Alexandre Yersin, a Swiss-French physician, finally isolated the bacterium Yersinia pestis during an outbreak in Hong Kong. This changed everything. Suddenly, it wasn't a ghost or a bad smell. It was a bug.
If you get the Black Death today—and yes, about 1,000 to 2,000 people still get it every year, including in places like New Mexico and Arizona—you don't need a chicken or a prayer. You need a pharmacy.
- Streptomycin: This is the heavy hitter. It’s an aminoglycoside antibiotic that has been the gold standard for treating bubonic plague for decades.
- Gentamicin: Often used today as a more readily available alternative to streptomycin.
- Doxycycline: A common antibiotic that works surprisingly well against the plague if caught early.
The "cure" is simply attacking the bacteria before it can trigger a massive inflammatory response in your lungs or lymph nodes. If you get antibiotics within the first 24 hours of symptoms, your chance of survival is over 90%. Without them? It’s still about 60% to 90% fatal.
The Lingering Threat
We talk about the plague in the past tense, but it’s still here. It’s endemic in rodent populations. In 2017, Madagascar had a massive outbreak of the pneumonic version—the kind that spreads through the air, not just flea bites.
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So, how did they cure the black plague? They didn't "cure" it so much as they learned to manage it. We got better at killing rats. We stopped throwing sewage into the streets. We discovered that tiny organisms cause disease, not "bad vibes" or the stars.
The real cure was a shift in human logic. We moved from superstition to sanitation.
Actionable Insights for the Modern World
While you probably won't encounter the Black Death at your local grocery store, the lessons from the 14th century are surprisingly relevant.
First, don't mess with wildlife. In the American West, the plague is carried by prairie dogs and ground squirrels. If you see a dead rodent, don't touch it. Your dog shouldn't touch it either. Fleas will jump from a cooling carcass to the nearest warm body—you.
Second, understand the power of early intervention. Most people who die of "ancient" diseases today do so because they wait too long to see a doctor. Symptoms of the plague look a lot like a severe flu: fever, headache, and chills. But the "tell" is the bubo—a painfully swollen lymph node. If you see that after being outdoors in an endemic area, get to an ER immediately.
Third, appreciate the infrastructure. We take trash pickup and closed sewer systems for granted. These are actually our primary defenses against the return of the plague. Keeping the rodent population away from human dwellings is 90% of the battle.
The Black Death changed the world. It ended feudalism because labor became so expensive (since everyone was dead). It sparked the Renaissance. And ultimately, it forced us to invent the field of public health. We didn't find a cure in a bottle; we found it in the way we organized our society.
Next Steps for Deep Historical Context:
To truly understand the impact of the plague, research the Statute of Laborers (1351). It was a law passed in England to stop peasants from demanding higher wages after the plague—a direct result of the population collapse. This will show you exactly how a medical crisis became an economic revolution. You might also look into the work of Dr. Paul-Louis Simond, who was the first to prove fleas were the vector, finally ending the "miasma" myth for good.