Antonine Plague

• 1. Introduction

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  The Antonine Plague came close to killing the orator Aelius Aristides in the city of Smyrna in 165, and that brush with death is the first documented case of an epidemic that would sweep the Roman Empire. It takes its name from the Antonine dynasty, whose emperors included Marcus Aurelius and Lucius Verus. It is also called the Plague of Galen, after the Greek physician who described it. Nobody today can say with certainty what the disease actually was. Nobody agrees on how many people it killed, either. This documentary asks why the empire was so vulnerable, how the sickness travelled, what it did to Rome's soldiers and cities, and whether it truly changed the course of history.

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• 2. A Crowded Golden Age

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  About 75 million people lived in the Roman Empire when the pandemic erupted, in the last years of the Pax Romana, the era often remembered as Rome's golden age. Historians generally agree that the empire's population peaked around the time the plague appeared, and then began to decline.

  Prosperity did not mean good health. About 20 percent of the population lived in one of hundreds of cities, a large share by ancient standards, and Rome alone held an estimated one million people. Historians call such cities a demographic sink. Deaths outnumbered births, so a steady stream of newcomers was needed just to keep the population level.

  Perhaps more than half of all children died before reaching adulthood, and life expectancy at birth was only in the mid-twenties. Crowding and poor sanitation made disease a constant companion. Wealth offered little shelter: only two of Marcus Aurelius' fourteen children are known to have survived to adulthood.

  Skeletons tell the same story. Studies of thousands of them show that the average Roman was shorter than people in pre-Roman Italy or in the Middle Ages. Historian Kyle Harper summed it up with the line: "not for the last time in history, a precocious leap forward in social development brought biological reverses."

  Epidemics were nothing new, with nine recorded between 43 BC and 148 AD. Yet this was the first known pandemic of the empire, because roads and sea lanes carried infection across vast territories faster than in any smaller, more confined society. The fastest travellers on those routes were soldiers, and soldiers were returning from the east.

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• 3. The Road From Seleucia

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  In the winter of 165-166, Roman forces besieged the Mesopotamian city of Seleucia during the Parthian campaign of Lucius Verus. Ancient sources agree that the plague most likely appeared there.

  The traditional Roman explanation was religious. Romans blamed their own army for violating a temple in Seleucia. The soldiers then carried the illness home from the Parthian Empire in early 166.

  From the east, the disease moved steadily westward. It reached Rome in 166, and by 172 it had touched nearly every corner of the empire. Ammianus Marcellinus reported that it spread to Gaul and to the legions stationed along the Rhine.

  The imperial family did not escape. The co-emperor Lucius Verus died of the plague in 169. In 166, the very year the disease reached the capital, a physician named Galen left Rome for his home in Asia Minor.

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• 4. Galen and the Mystery

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  Galen returned to Rome in 168, summoned by the two Augusti, the co-emperors Marcus Aurelius and Lucius Verus. He was present when the disease struck troops stationed at Aquileia in the winter of 168/69.

  He set down a brief account in his treatise Methodus Medendi, meaning "Method of Treatment." He also scattered references to the epidemic through his many other writings. Galen called the plague "great" and long-lasting. He listed fever, diarrhea and pharyngitis, along with a skin eruption, sometimes dry and sometimes pustular, that appeared on the 9th day of illness.

  Scholars have generally preferred smallpox as the diagnosis, partly because of eruptions across the whole body that looked red and black. Yet Galen's description is not completely consistent with smallpox. Recent genetic evidence also strongly suggests that the most severe form of smallpox did not arise in Europe until much later. Measles has been proposed as an alternative.

  Historian William H. McNeill argued that the Antonine Plague and the later Plague of Cyprian, which lasted from 251 to about 270, were two different diseases. One would have been smallpox and the other measles, though not necessarily in that order. The heavy toll in Europe may suggest that people had no earlier exposure to either illness, while survivors gained immunity.

  Other historians believe both outbreaks were smallpox. They point to molecular estimates placing the evolution of measles sometime after 1000 AD. As yet, no genetic evidence from the Antonine plague itself exists, so the question stays open.

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• 5. Counting the Dead

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  The Roman historian Eutropius stated that a large proportion of the empire's population died in this outbreak. Cassius Dio, a contemporary Roman historian, described a fresh outbreak in 189 that killed up to 2,000 people a day in the city of Rome. That figure represented 25 percent of those who fell ill. Whether that later epidemic was a new disease or a return of the old one, and whether it reached beyond Rome, is unknown.

  Modern totals vary widely. One commonly cited estimate puts the death count at 5-10 million, roughly 10 percent of the empire. The widest range runs from 2 to 33 percent of the population, or between 1.5 and 25 million people. Most estimates settle near 10 percent, about 7.5 million, with death rates of up to 15 percent in the cities and the army.

  The diagnosis matters for the arithmetic. If the disease was smallpox, whose survival rate is often around 75 percent, about a quarter of those infected would have died. Cities and soldiers suffered most, and the army's losses arrived at a dangerous moment.

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• 6. An Army Reduced

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  In 166, as the plague spread, the Marcomannic Wars began. Germanic tribes invaded Roman territory south of the middle Danube, in what is now the Czech Republic and Slovakia, and pushed south toward Italy.

  Ancient chroniclers portrayed the army as "reduced almost to extinction." The plague thinned the ranks and weakened Rome's strategic position at the same time. Marcus Aurelius had to recruit and train new soldiers from among "gladiators, slaves, and bandits."

  After a delay of two years, the emperor launched an attack on the Germanic tribes in 169. By 171, the Roman army had driven the invaders out of Roman territory. The fighting continued on and off until 180, when Marcus Aurelius died, possibly of the plague.

  The long conflict fed a cycle of instability along the frontier. The plague may also have struck the Germanic tribes, though the record is thin. How much damage the disease did to Rome as a whole remains one of the sharpest disagreements among historians.

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• 7. A Fall or a Stumble

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  Barthold Georg Niebuhr, who lived from 1776 to 1831, gave the classic verdict. He wrote that the reign of Marcus Aurelius was a turning point in so many things, above all literature and art, and that he had no doubt this crisis was caused by the plague. In his words, "The ancient world never recovered from the blow inflicted on it by the plague which visited it in the reign of Marcus Aurelius."

  Kyle Harper has argued something similar. In any account of Rome's destiny, he wrote, the pandemic "merits a place squarely in the forefront."

  A team of six historians pushed back. They questioned the "extreme" position of Harper and others as "ignoring scholarship that suggests it had a less than catastrophic outcome." Even so, they affirmed that "we do not doubt that disease and climate had some of the impact Harper describes." To some scholars the plague was only slightly deadlier than the epidemics that often hit parts of the empire.

  Some historians have guessed that fear of the disease boosted the cult of Asclepius, the god of medicine. The epigraphic record, meaning inscriptions, shows no such rise in his popularity.

  The archaeological record does show one clear casualty. Roman trade across the Indian Ocean, from the ports of Roman Egypt to the Indian subcontinent and Southeast Asia, seems to have suffered a major setback. That disruption likely contributed to broader economic decline and social instability in the following years.

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• 8. Climate and Contagion

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  A very rare class of eruption, rated VE7, is dated to 173 at Taupo in New Zealand. The timing falls within the plague years, and it fits a wider pattern that researchers have drawn out.

  According to 2024 research, the major plagues that struck Rome were strongly linked to cooler and drier climate. These were the Antonine Plague, the Plague of Cyprian and the Plague of Justinian. The finding suggests that colder weather may have helped these diseases spread.

  The researchers think climate stress did not act alone. It interacted with social and biological factors such as food availability, rodent populations and human migration, leaving populations more susceptible to disease. Rome's first great pandemic may therefore have been the first of a series, rather than a single misfortune.

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