Yersinia Pestis, and Other Plagues

In late 1346, the Genoese trading settlement at Caffa on the Black Sea was besieged by Mongol Tartars seeking to oust the Genoese from the town. The Tartars brought war with them, but also disease; Central Asia had been suffering from a plague epidemic for several years before.

By April, 1347, the majority of besiegers and townspeople were dead of either battle or illness. The remaining Genoese abandoned Caffa and fled westward to Constantinople, to Messina in Sicily, to Genoa itself, and to French Mediterranean ports. When the Genoese galleys arrived in the Italian and French ports, they carried dead and diseased passengers, and rats. The passengers carried the wildly contagious pneumonic form of the bubonic plague. The rats carried fleas, who in turn carried the bacterium yersinia pestis, the organism responsible for bubonic plague. By late 1347, the plague had spread throughout Italy; by January, 1348, it had reached France, Spain, Portugal, and England. Later that year, it reached Germany and the Low Countries.

By the end of 1350, something between one third and one half of the population of Western Europe was dead, including half of the population of Paris and as much as two-thirds of the populations of London, Florence, Hamburg, and Bremen. Fully 20 percent of the roughly 170,000 villages and towns that had existed in Germany before 1348 vanished completely in the three years of the Great Mortality, the Black Death. The European world was changed utterly, to an extent that even two much-later world wars couldn’t match.

Medieval people understood more about the mechanism of disease than we sometimes assume today. They understood the idea of contagion, that people who were exposed to people who were sick could get sick themselves. Having no understanding of bacteria, they still understood that something unseen — perhaps the breath, perhaps something else — could pass disease from one person to another. Some people, notably the Moors in Spain and perhaps Guy de Chauliac, physician to Pope Clement VI in Avignon, had some inkling that hygiene could have an impact on the spread of the plague, though they didn’t know why. Some people tried to avoid spices and other goods that might have been on Genoese ships, believing that those goods might somehow “store” the plague. Many people understood that people who had had the plague and somehow recovered were unlikely to get it again.

Of course, their understanding was incomplete. They didn’t understand the roles of yersinia pestis, or of rats or the fleas they carried. Most of all, though, they had no tools with which to fight the plague, beyond time and prayers. They attempted to retard its advance by banning ships and travelers from plague areas, and by burning huge fires in the hope that the smoke would stop the plague. But nothing worked; the plague continued to move through Europe. They had no way to make it stop.

By the time the plague reached France in 1348, a conspiracy theory — fake news, if you will — had arisen. The theory offered people the gift of believing that they could control the plague, and the hope that they could, in fact, make it stop. The idea was that the plague was caused by the Jews, either through poisoning the wells or through the application of witchcraft.

Everyone knew, at least in their inner hearts, that this was a lie. It was widely understood that the plague arrived on ships from Central Asia, and that it was spread at least in part by contact with the sick. But the complex truth didn’t offer the easy way out provided by the simple lie, and murders of Jews began. The first massacre was in Toulon, France, in April, 1348, and the anti-Jewish movement spread as fast as the plague through the rest of Western Europe, first to Portugal and then to Germany, Switzerland, and the Low Countries.

In 1348, Pope Clement VI, inspired by charity, common sense and his physician Guy de Chauliac, issued two papal bulls stating forcefully that the Jews were not responsible for the plague, saying that those who blamed the Jews “had been seduced by that liar, the devil.” But the bulls had little effect; even the threat of damnation could not overcome that most powerful of human ideas, the idea that if we can get rid of those people who are different from us, our troubles will be over.

By mid-1349, over 500 Jewish communities had been destroyed. Huge numbers of Jews were stoned to death, lynched, or burned at the stake, with notable massacres in Aragon, Flanders, Strasbourg, and many other places. In January, 1349, the entire Jewish population of Basel was burned; in March of the same year, the people of the city of Erfurt killed every Jew residing there. On a single day in August, 1349, the 6,000-member Jewish community in Mainz, the largest Jewish center in Europe, was eradicated. Jews in some communities killed themselves to escape the persecution; others fled east to Poland, where King Casimir III offered them sanctuary.  By 1350, there were virtually no Jews remaining in the Low Countries or in most of Germany. From that point forward, the majority of European Jews — 70% or more — resided east of Germany, primarily in Poland. The effect of the plague conspiracy theory had shifted the center of Ashkenazi Jewish culture from Western Europe (primarily Germany) to the east.

For six hundred years after the Great Mortality, Europe’s Jews survived and sometimes prospered, through purges and czarist pogroms in the east and the Inquisition and subtler actions in the west. By 1939, there were 9.5 million Jews in Europe, about 55 percent of the world’s Jewish population of around 17 million. Of the European Jews, roughly two-thirds, six million or so, lived east of Germany, 3.5 million in Poland alone.

We know what happened then: the Greatest German Liar convinced his people that “Jewish Bolshevists” were intent on destroying Aryan culture, thus creating a new edition of if we can get rid of those people who are different from us, our troubles will be over. By 1945, six million European Jews had been murdered. Almost all of Poland’s 3.5 million Jews were lost; after the war, it was estimated that perhaps 120,000 — about four per cent — were still alive. Today, 70 years after the Holocaust, the Jewish population of the world has reached about 14 million, or just over 80 per cent of what it was in 1939. Fewer than 20 per cent of these live in Europe.

The history of European Jewry is to a large extent the history of if we can get rid of those people who are different from us, our troubles will be over. The Jews are not alone in this, of course; this is also the history of Europe’s Roma population and to some extent of America’s Native Americans, to name just two groups. Apparently we cannot learn, still today, that leaders and movements who arrive with the message if we can get rid of those people who are different from us, our troubles will be over are always lying, and will never bring us anything good. Every world religion I know anything about contains parables and stories designed to counter this idea. St. Luke gave us the parable of the Good Samaritan, and there are many others. But they haven’t been able to put a dent in this most powerful, seductive lie.

I find myself thinking of Pope Clement and his warning to 14th-century Europeans that they had been “seduced by that liar, the devil.” But he couldn’t convince his people then. No one has convinced us yet.


For those who would like to know more about the Great Mortality of 1348 – 1351, I recommend the book The Great Mortality, by John Kelly (Harper Collins, 2005). For more information about the Nazi Holocaust, I’d suggest starting with the web site of Yad Vashem.


10 thoughts on “Yersinia Pestis, and Other Plagues

  1. Bravo. Part of the problem in this country is the widespread belief in that “elitism” is ruining us. It gives the uneducated and anti-education crowd a reason to feel that their ill-informed ideas are somehow superior to science and critical thought. There is a general disdain for any history that doesn’t feature great gun fights. It’s hard to not repeat mistakes when one makes no attempt to learn about them.


  2. Most impressive, Sue. I never expect non Jews to have this kind of understanding or even make the attempt. Thank-you!


  3. Very interesting and informative. I did not know that anti-semitism used the plague as an excuse way back then. I’m going to pick up The Great Mortality. In the second half of the twentieth century, I grew up in a township west of Philadelphia that had a vibrant Jewish population and at least half of my classmates from grade school through high school were always Jewish. I never thought of them as different as a group, they were just other kids and often my friends. I don’t understand how non-Jews see Jews as different. What is different? Furthermore, I am very curious about the earliest origins of anti-semitism on planet Earth. Sue, do you know?


    1. I have read that Christian anti-semitism dates from about the 4th century, when Christianity became the official religion of the Roman Emperor under Constantine. Constantine himself instituted some anti-Jewish measures in Roman law. Roman measures against the Jews in Palestine pre-date that, however.


      1. So this suggests that the roots of anti-semitism begin with the rise of Christianity and had no existence before. But how would you describe the woes and suffering of the Israelites in the old Testament? Was that just par for the course in ancient times, trying to keep your people safe? And then when Christianity came along, those generic City States survival challenges became institutionalized as a targeted persecution of Jews?


      2. I can’t really speak to this, except to say that I think the Old Testament persecutions of the Jews may have been different. A lot of the details of the OT period are list to us, for on thing…but I also don’t know a great deal about the period 🙂


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