Constantinople was one of the most prosperous cities of the medieval world. Its position as a gateway between East and West turned it into a thriving centre of trade, and was a major factor in the power of the Byzantine Empire. But this prosperity came at a price. The constant flow of people and goods over the docks left Constantinople uniquely vulnerable to any plague that was loose in the world, and the ravages of these diseases often critically weakened the Empire.
Plague was something the Byzantines had some familiarity with through their Roman ancestry. In the second and third century AD, Rome was ravaged by two plagues in short succession, the Antonine Plague and the Cyprian Plague. The Antonine Plague not only devastated the Roman population (between a quarter and a third of the Empire’s population was killed), but it struck particularly hard at the army, and even claimed the life of the co-Emperor, Lucius Verus. The Cyprian Plague also claimed the life of an Emperor, Claudius II, in 270AD. It devastated the Roman people and the army as well, although it struck just as hard at the enemies of Rome. What these two plagues were remains uncertain – the symptoms suggest either smallpox or measles, although measles is not thought to have evolved until 500AD. On the other hand, the devastation of the Cyprian plague rules against both diseases being smallpox, as the first outbreak would have left some immunity to the survivors. Ultimately (unlike some of the plagues we discuss later), we may never actually know.
The first major plague to strike at Constantinople was the Plague of Justinian, named for the Byzantine Emperor who was in power in 541AD when the plague appeared. He did in fact contract the disease, but he was one of the few to survive it – fully 40% of the population of Constantinople were not so lucky. It’s thought that the disease originated in China, and spread west, coming into the city via rats on grain barges from Egypt – it is believed to have been a forerunner of the bubonic plague, carried by fleas on the rats. While the initial outbreak only lasted a year, it had a devastating effect. Between five and ten thousand people a day died in the city, with an equivalent number dying in the countryside surrounding it. The loss of manpower led to a rise in the price of grain, combined with a drop in the amount of tax revenue that crippled the Empire financially as well as leaving it vulnerable to foreign invaders such as the Goths. While the disease did spread out further west (with cases being reported as far away as Denmark and Ireland), it did not strike them as hard and so left them at an advantage. Justinian was well on his way to reconquering the lands formerly held by the Western Roman Empire, utterly changing the course of history and it’s believed that the plague is the only thing that stopped him. The plague returned several times over the next two hundred years, with the last outbreak occurring in 750AD. The constant weakening of the Empire combined with the other world-changing events (such as the Battle of Yarmouk) going on at the same time played a pivotal role in preventing the expansion of the Empire, leading to its eventual stagnation.
But if the Plague of Justinian was what kept the Byzantine Empire from conquering the world, it was a more famous plague that would help to destroy it. The Black Death, the most notorious of historical plagues, came to Constantinople in July of 1347, once again coming from the east (where it had killed over 30 million people in China, a quarter of the population). From Constantinople it spread along the trade network to Sicily, Marseilles and Alexandria. In Europe it killed fifty million people – over half of the entire population. Its effect on Constantinople was just as devastating. While the population of Constantinople was between 400,000 and 1,000,000 at its height, it had only recovered to a total of 50,000 when the city fell a century later. The plague returned repeatedly throughout the world, and struck at Constantinople multiple times both before and after it fell, even right up to relatively recent times (with 68 recorded outbreaks in the city over the 18th century). Plague was a fact of life now – and right in the centre of the world was no longer such a great place to be.