Plague of Justinian

The Plague of Justinian (541–542) was a pandemic that afflicted the Eastern Roman (Byzantine) Empire, especially its capital Constantinople, the Sassanid Empire, and port cities around the entire Mediterranean Sea. One of the deadliest plagues in history, this devastating pandemic resulted in the deaths of an estimated 25 million (at the time of the initial outbreak that was at least 13% of the world's population) to 50 million people (in two centuries of recurrence).

In 2013 researchers found that the cause of the pandemic was Yersinia pestis, the bacterium responsible for bubonic plague. The plague's social and cultural impact during the period of Justinian has been compared to that of the similar Black Death that devastated Europe 600 years after the last outbreak of Justinian plague. The principal historian during the 6th century, Procopius, viewed the pandemic as worldwide in scope. Genetic studies point to China as having been the primary source of the contagion.

The plague returned periodically until the 8th century. The waves of disease had a major effect on the future course of European history. Modern historians named this plague incident after the Eastern Roman Emperor Justinian I, who was emperor at the time of the initial outbreak; he contracted the disease himself yet survived.

The Plague of Justinian is generally regarded as the first recorded instance of bubonic plague. This conclusion is based on the historical description of the clinical manifestations during the epidemic and the detection of Y. pestis DNA from human remains at ancient grave sites dated to that period. A genetic study of the bacterium causing bubonic plague based on samples taken from the remains of 14th-century plague victims in London and a survey of other samples suggests that the Plague of Justinian and others from antiquity arose from either now-extinct strains of Yersinia pestis genetically distinct from the 14th-century strain or came from pathogens entirely unrelated to bubonic plague. However, further work by the same researchers noted that the spread of several unusual modern variants of plague worldwide can be dated to an evolutionary radiation event approximately coinciding with the Plague of Justinian, supporting the notion that it was caused by a strain of bubonic plague.

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