Plague of Justinian
The Plague of Justinian struck the Byzantine Empire, killing up to 25 million people
January 01, 541
The First Great Plague Pandemic
The Plague of Justinian struck the Byzantine Empire beginning in 541 AD during the reign of Emperor Justinian I. It was caused by the bacterium Yersinia pestis — the same pathogen responsible for the Black Death eight centuries later. The plague arrived via grain ships from Egypt and spread through the port cities of the Mediterranean. Constantinople, the empire's capital, was hit hardest. At its peak, chroniclers reported as many as 10,000 deaths per day in the city, though this figure may be exaggerated.
How It Spread and Who It Killed
The disease spread through bites from infected fleas that had fed on infected rats. Symptoms included swollen lymph nodes (called buboes), fever, and rapid deterioration. Death often came within days. The plague struck repeatedly in waves across the Mediterranean world between 541 and about 750 AD, killing an estimated 25 to 50 million people — perhaps half the population of the Byzantine Empire. Justinian himself caught the plague but survived, one of the few rulers to do so.
The Plague's Historical Impact
The Plague of Justinian halted Justinian's ambitious campaign to reunite the old Roman Empire. Entire regions were depopulated, tax revenues collapsed, and military recruitment became impossible. Some historians argue it contributed to the weakening of Byzantine power and helped create the conditions for the Arab conquests of the 7th century. Ancient DNA analysis of burial sites, conducted in the 2010s, confirmed the presence of Yersinia pestis — finally establishing the biological identity of the disease that changed the ancient world. Use our date calculator to see how long ago this plague began.