plague of Justinian, plague pandemic that spread throughout the Mediterranean region and beyond beginning about 541 CE. It is named for Justinian I, who was the Byzantine emperor at that time.

　　Although there is evidence that bubonic plague has been around for as long as humankind, the plague of Justinian is the first documented outbreak of a bubonic plague pandemic. The 6th-century historian Procopius wrote about the Byzantine Empire during Justinian’s reign, and he recounts the devastation wreaked by the plague on Constantinople (later renamed Istanbul), at that time the most important political and cultural center of the Western world and the hub of Christian civilization.

　　Britannica Quiz Disasters of Historic Proportion The plague, casued by the bacterium Yersinia pestis, appears to have started in the port of Pelusium in Lower Egypt about 541 and then spread across the Mediterranean in the ships that transported grain to the heart of the empire. The first few cases appeared in Constantinople in the spring of 542, where Justinian himself fell ill but then recovered. The disease soon took hold and raged for four months. Justinian ordered vast pits to be dug to dispose of the rotting corpses; when these overflowed, bodies were stuffed into the towers of the city walls with quicklime poured over them to speed up decomposition, or they were loaded onto ships that were pushed out into the Sea of Marmara and set alight. Constantinople came to a standstill, food started to run out, and law and order broke down. At its height, perhaps as many as 10,000 people a day were dying in Constantinople. By the time the plague had run its course, nearly half the city’s population was said to have died.

　　The plague spread east to the Caucasus, infecting invading Persian armies, and west throughout Europe, where it became endemic, with localized outbreaks occurring for the next two centuries, disappearing entirely about 750. However, the worst was over by 590. It is impossible to be certain of the mortality rate during this outbreak. Estimates vary between 25 million and 100 million deaths. It was received wisdom that about a third of Europe’s population had been wiped out, but on the strength of the evidence modern medical historians believe that figure is exaggerated and based on analogy with the Black Death. Not until that latter plague ravaged Europe would a pandemic on the scale of the plague of Justinian be experienced again.

　　Some historians regard the plague of Justianian as the dividing line between late antiquity and the beginning of the Middle Ages.

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