The plague has killed an estimated 75 to 200 million people across three major pandemics spanning roughly 1,500 years. The deadliest single wave, the Black Death of the 14th century, wiped out around 50 million people in Europe alone between 1346 and 1353, roughly half the continent’s population at the time.
The Black Death: 1346 to 1353
The Black Death is the event most people picture when they think of “the plague,” and for good reason. It killed approximately 50 million Europeans in just six years, reducing the continent’s population by an estimated 50 to 60 percent. Research into English manorial records, which tracked tenant deaths in detail, produced a particularly reliable estimate: England’s population dropped from 4.8 million in 1348 to 2.6 million in 1351, a decline of 46 percent in three years.
That devastation wasn’t evenly distributed, though. A 2022 study from the Max Planck Society found that some regions suffered catastrophic losses while others barely registered the pandemic. Scandinavia, France, southwestern Germany, Greece, and central Italy show sharp agricultural declines consistent with massive death tolls. But much of Central and Eastern Europe, along with parts of Ireland and the Iberian Peninsula, show evidence of uninterrupted population growth. The long-held assumption that the Black Death killed a uniform percentage of people everywhere in Europe no longer holds up.
Beyond Europe, large outbreaks are clearly visible in historical records from Western Asia, the Middle East, and North Africa, but comprehensive death toll estimates for these regions don’t exist. Contemporary accounts describe staggering single-day death counts in cities like Tunis and Tlemcen, but historians caution against treating medieval figures as modern statistics or projecting urban death rates onto rural and nomadic populations. For North Africa in particular, separating plague deaths from deaths caused by concurrent wars and famines is essentially impossible. China also experienced enormous population decline during this period, tied to both the plague and the political upheaval of the Yuan-to-Ming dynasty transition, but isolating the disease’s specific toll remains difficult.
The Plague of Justinian: 541 to 750 CE
The first recorded plague pandemic struck the Byzantine Empire in 541 CE and recurred in waves for roughly two centuries. Traditional estimates place the death toll somewhere between 15 and 100 million people, or 25 to 60 percent of the Late Roman Empire’s population. That enormous range reflects genuine uncertainty. Molecular research has confirmed that the same bacterium responsible for the Black Death caused the Justinian Plague, but the historical evidence for precise mortality is far thinner than what exists for the 14th century.
Some recent scholarship has pushed back on the highest estimates, arguing that the Justinian Plague may have been less catastrophic than previously believed. The debate is ongoing, but even conservative readings place the death toll in the tens of millions.
The Third Pandemic: 1894 to 1959
The most recent plague pandemic originated in Yunnan, China, and spread to Hong Kong in 1894, then radiated outward to port cities worldwide. Over the next 65 years, it killed more than 15 million people. The vast majority of those deaths occurred in India, where the disease tore through densely populated regions with limited public health infrastructure. This pandemic was also scientifically significant: it was during the Hong Kong outbreak that researchers first identified the bacterium that causes plague, eventually enabling the development of antibiotics that could treat it.
Notable Outbreaks Between Pandemics
Plague didn’t only kill during the three major pandemics. It returned to European cities repeatedly for centuries after the Black Death. The Great Plague of London in 1665 officially killed 68,596 people, though the true number was likely over 100,000. At its peak in September of that year, more than 7,000 Londoners died in a single week. Similar outbreaks struck cities across Europe well into the 18th century.
Why the Plague Killed So Many
Plague comes in three forms, and all of them are exceptionally lethal without treatment. The bubonic form, spread through flea bites, kills about 60 percent of untreated patients. The pneumonic form, which infects the lungs and spreads person to person through coughing, is almost always fatal without antibiotics. Even with prompt modern treatment, pneumonic plague still kills around 30 percent of patients. The septicemic form, which enters the bloodstream directly, approaches 100 percent mortality if untreated.
In the medieval world, none of these forms could be treated. People had no understanding of bacteria, no antibiotics, and no effective way to quarantine at scale. Fleas carried the disease from rats to humans in crowded, unsanitary conditions that were standard for the era. Once the pneumonic form took hold in a community, it could spread through the air like a respiratory illness, accelerating transmission far beyond what flea bites alone could produce.
Plague Today
The bacterium that caused all three pandemics still exists. In the United States, an average of seven cases are reported each year. Globally, most cases since the 1990s have occurred in Africa, primarily in small towns, villages, and agricultural areas rather than cities. Modern antibiotics are highly effective when administered early, which is why plague is no longer the civilizational threat it once was. But it has never been eradicated, and small outbreaks continue to surface in parts of Africa, Asia, and the Americas.