What Was the Plague of Justinian? The First Pandemic
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In the spring of 542 the emperor Justinian, who had reconquered Italy and North Africa and was rebuilding the Roman Empire from Constantinople, fell ill with swellings in the groin and armpits, and in the city around him the dead were being thrown into the towers of the walls because the burial grounds were full. He survived; between a quarter and half of the city did not. The disease was bubonic plague, the same that would return as the Black Death eight centuries later, and this was its first recorded appearance, a pandemic that ran for two hundred years and that modern DNA has traced to a strain now extinct.
Where it came from
The historian Procopius, who was in Constantinople, wrote that the disease began in Egypt at Pelusium in 541 and spread in both directions along the coast, reaching the capital the following spring by the grain ships from Alexandria, which carried the rats and the fleas that carried the bacterium. Where it entered Egypt is less clear; the DNA of the strain recovered from sixth-century graves in Germany, Britain, France and Spain shows it descends from a lineage of Yersinia pestis native to Central Asia, and it probably travelled by the trade routes through the Red Sea or the steppe. The bacterium lives in the fleas of wild rodents, kills the rats it reaches first, and moves to humans when the fleas run out of rats; in a city of half a million people living on grain, the rats were everywhere.
What it did
Procopius, who had read Thucydides on the plague of Athens and imitated him, describes the symptoms with a doctor's precision: sudden fever, then within a day or two the buboes, swellings of the lymph glands in the groin, armpits and neck, then delirium, coma or death in most cases within days. At the height of the outbreak in Constantinople he put the deaths at 5,000 a day and, on some days, 10,000; the historian John of Ephesus, travelling through Syria and Asia Minor, described villages with no one left to bury the dead and fields of ripe grain with no one to harvest them. Estimates of the mortality across the empire range from 15 to 40 percent of the population, and the disease came back in waves roughly every decade until about 750, when it stopped, for reasons nobody knows, and did not return to Europe until 1347. The marks it left:
- •Constantinople's population fell by perhaps half, and the empire's tax base and army with it
- •Justinian's reconquests stalled: the war in Italy dragged on for a decade more with too few troops, and the Lombards took most of the peninsula in 568
- •Wages rose and the emperor legislated against them, as English kings would after the Black Death
- •The Persian Empire was struck as hard, and both empires were weakened when the Arab armies arrived a century later
- •Farmland went out of cultivation, cities shrank, and the long decline of the ancient urban world in the eastern Mediterranean accelerated
The argument about its size
Not every historian accepts the catastrophe. A school of revisionists, most vigorously since 2019, has argued that the literary sources exaggerate, that the archaeology shows no sharp break in coins, pottery, building or land use in the sixth century, and that the plague was a serious epidemic rather than a civilisation-ending one. The maximalists reply that the graves, the DNA and the laws are exactly what a demographic disaster leaves, that the papyri of Egypt show tax receipts falling, and that a lack of visible rupture is what one expects when the survivors keep living in the same houses. The truth is being argued in pollen cores, ice cores and the isotopes of skeletons, and the range of estimates has narrowed but not closed.
The bacterium in the graves
For a century historians debated whether the Justinianic plague was really bubonic plague at all, since Procopius's account, though vivid, could fit other diseases. The answer came from teeth. In 2013 geneticists extracted Yersinia pestis DNA from two sixth-century skeletons in a Bavarian cemetery, and sequences from Britain, France, Spain and Germany have followed; the strain is a distinct branch of the plague family tree, separate from the Black Death's and from the plague that persists in rodents today, and it appears to have died out after the eighth century. The finds also showed how far the pandemic reached, since a rural cemetery in Cambridgeshire and a village in Bavaria are a long way from the grain ships of Alexandria, and they settled the identity of a disease that its chroniclers described without knowing what a bacterium was.
Why it matters
The Plague of Justinian is the first pandemic in history that can be followed from its outbreak, and it sits at the hinge between the ancient world and the medieval one. The empire that Justinian had nearly rebuilt did not recover its strength, the Mediterranean that Rome had unified became a frontier between Christendom and Islam within a century, and the population of Europe did not regain its Roman level until about 1000. Whether the plague caused those things or merely accompanied them is the argument, and the bacterium, extracted from the teeth of people who died of it fifteen centuries ago, has at least settled what it was.
The takeaway
The Plague of Justinian was the first recorded pandemic of bubonic plague, arriving in Egypt in 541, reaching Constantinople by the grain ships in 542 and recurring for two centuries, killing somewhere between a sixth and two fifths of the eastern Roman Empire and weakening it on the eve of the Arab conquests. Identified from Yersinia pestis DNA in sixth-century graves across Europe as a strain now extinct, its scale is still argued between those who read the chronicles and those who read the archaeology.