The Plague Never Left: How the Black Death Is Still Killing People Today

Four ships came into the harbour at Messina, Sicily, in October 1347, and almost everyone on board was already dead or dying. The few sailors still standing were burning with fever, delirious, and covered in swellings the size of eggs in their armpits and groins. The Sicilians did the only sensible thing available to them: they ordered the "death ships" back out to sea. It didn't matter. The rats had already got off, and so had the fleas riding on them, and within four years the disease those fleas were carrying would kill somewhere between a third and half of everyone living in Europe. People at the time didn't even have a settled name for it. They called it the Great Mortality, or simply the Pestilence. The label most of us know, the Black Death, wasn't widely used until centuries later, coined by Scandinavian and German writers translating a Latin phrase, atra mors, that could mean either "black" or "terrible" death and was probably meant as the second.

What was actually happening inside people

Strip away the panic and the plague is a bacterial infection, Yersinia pestis, and it does one of three fairly specific things to a human body depending on how it gets in. Bubonic plague, the most common form, arrives through a flea bite and swells the nearest lymph nodes into the painful, blackened lumps called buboes, in the groin, armpit or neck. Left untreated it kills perhaps three in every five people it infects, usually within a week. Septicemic plague gets straight into the bloodstream and causes the skin itself to blacken and die in patches from internal bleeding, which is very possibly where the "black" actually comes from, whatever the etymologists say about atra mors. Pneumonic plague is the one to actually fear: it settles in the lungs, spreads directly from person to person through coughing rather than needing a flea at all, and can kill within twenty-four hours of the first symptom. Without modern antibiotics, all three forms are frequently fatal. With them, caught early, plague is entirely curable. That single fact is the hinge this whole article turns on.

A third of a continent, and a strange silver lining

Historians argue over the exact numbers, because nobody was keeping careful census data in 1348, but the low estimate for European deaths in the first wave is around 25 million and the high estimate pushes past 50 million, out of a continent of perhaps 80 million people. Whole villages simply stopped existing. Harvests rotted in the fields because there weren't enough living hands left to bring them in. And out of that horror came something almost nobody would have predicted while it was happening: a labour shortage so severe that it broke the economic logic of the entire medieval system. With a third or more of the workforce gone, the peasants who survived suddenly had leverage they had never had before, and they used it, demanding higher wages and better terms from landowners who had no choice but to pay up or watch their fields go fallow. England's Peasants' Revolt of 1381 grew directly out of the tension that leverage created. Historians now treat the Black Death as one of the events that ended serfdom in Western Europe, not because anyone planned it that way, but because a catastrophe that killed a third of the population also, almost by accident, gave the survivors a stronger hand than they had held in centuries.

Panic needs someone to blame

None of that made the years 1348 and 1349 any less terrifying to live through, and terrified people go looking for someone to blame. Flagellant processions, groups of penitents who marched from town to town whipping themselves bloody in public in the hope of appeasing an angry God, spread across German-speaking Europe. And in dozens of towns, mobs turned that fear into violence against Jewish communities, accusing them of poisoning wells, and burning or expelling residents in massacres that Pope Clement VI explicitly condemned at the time, to little effect. It is a documented irony of the period that some Jewish communities, following religious hygiene practices around handwashing and burial, in places suffered somewhat lower plague mortality than their neighbours, a fact panic-stricken accusers turned into further "evidence" of guilt rather than a clue about the actual cause. Nobody in 1349 had any way of knowing the real explanation involved fleas and rats. The gap between not knowing and needing an answer anyway is where the worst of that century happened.

It kept coming back

The first wave ending in 1351 wasn't the end of the story, just the end of the worst chapter. The plague returned to Europe roughly once a decade for the next hundred and thirty years, and kept flaring up in smaller outbreaks for centuries after that, which is a large part of why Europe's population didn't fully recover to its pre-1347 level until the 1500s. The Great Plague of London in 1665 killed around 100,000 people, close to a fifth of the city, and remains the country's last major outbreak. For over five hundred years after those four ships docked at Messina, doctors treated plague with theories about bad air, imbalanced bodily humours, and eventually the beaked masks stuffed with dried flowers that plague doctors wore from the 1600s onward, on the theory that foul smells themselves carried disease. All of it was well-intentioned. None of it worked, because nobody yet knew what was actually causing the deaths.

Finally, an actual answer

That changed in 1894, during a third global wave that had broken out forty years earlier in the mountains of East Asia and was, by then, reaching port cities across the region. A French scientist named Alexandre Yersin, working in Hong Kong, isolated the bacterium responsible and it was eventually named Yersinia pestis after him. Four years later, a French physician named Paul-Louis Simond proved the mechanism that had puzzled everyone for five and a half centuries: it wasn't foul air, and it wasn't even really the rats. It was the fleas living on the rats, which is why plague could jump to a person who had never touched a rodent in their life. That third pandemic wave went on to kill an estimated twelve million people on the Indian subcontinent alone over the following decades, the overwhelming majority of its global toll, a death count that rarely gets mentioned in the same breath as 1347 despite being staggering in its own right.

Cured, not gone

Here is the part that should genuinely unsettle you: the bacterium that caused the Black Death is not extinct, has never been extinct, and is not going to become extinct. It lives on in wild rodent populations across large parts of the world, and it still infects people. The World Health Organization records something like 1,000 to 2,000 confirmed plague cases globally most years, with Madagascar and the Democratic Republic of the Congo accounting for the bulk of them, and the rural southwestern United States, New Mexico especially, logging a handful of cases most summers from wild rodent fleas. In 1943, doctors used the newly available antibiotic streptomycin to treat plague successfully for the first time, and modern antibiotics now make bubonic plague entirely survivable if it's caught within the first day or two. Untreated, the mortality rate hasn't changed at all since 1347. A 2022 genomic study finally nailed down where the whole thing started, tracing the Black Death's ancestral strain to 700-year-old burials near Lake Issyk-Kul in the mountains of Central Asia, closing a question that had been open since Yersin's discovery.

So the plague isn't a story that ended. It's a disease that a handful of unlucky people, most years, still catch from a flea bite while camping or gardening, that still shows up in hospital labs, and that modern medicine can now cure in days rather than letting it kill in days, provided anyone notices in time. The four ships at Messina are seven centuries gone. The bacterium that came off them is still out there, and it is only antibiotics, discovered less than a hundred years ago, standing between that fact and a repeat.

Sources

• Wikipedia, "Black Death" (overview, the 1347 arrival at Messina, death toll estimates, and the flagellant movement).
• History.com, "Black Death" (the siege of Caffa, the four ships, and the term's later origin).
• CDC, "Plague: Signs and Symptoms" (bubonic, septicemic, and pneumonic plague and their mortality without treatment).
• World Health Organization, "Plague" (global case counts, treatability with antibiotics, and current endemic regions).
• CDC, "Plague in the United States" (recent human plague cases in the American Southwest).
• Nature, Spyrou et al., "The source of the Black Death in fourteenth-century central Eurasia" (2022; the Lake Issyk-Kul ancestral strain).
• Wikipedia, "Third plague pandemic" (the 1855 outbreak, Yersin's 1894 discovery, Simond's 1898 flea-transmission proof, and the Indian death toll).
• Britannica, "Peasants' Revolt" (the 1381 English revolt and its roots in post-plague labour conditions).