Antonine Plague

From about AD 165 to 180 a long and deadly epidemic swept across the Roman Empire, the first pandemic known in its history. It is named after the ruling Antonine dynasty of Marcus Aurelius and his co-emperor Lucius Verus, and is sometimes called the Plague of Galen after the physician who described it. Its cause is still uncertain, and estimates of the dead vary enormously, with many historians settling on about a tenth of the empire's population.

The plague struck at the end of a long period of relative peace and prosperity, when the empire's population, perhaps around 75 million, was probably at its peak. Yet conditions favoured disease. Perhaps a fifth of the population lived in cities, where deaths outnumbered births and sanitation was poor; Rome alone may have had a million people. Average life expectancy at birth was perhaps 25 years. Roads and shipping lanes that bound the empire together also carried infections quickly from one region to another.

Roman tradition blamed soldiers who had desecrated a temple at Seleucia, on the Tigris, during Lucius Verus's war against the Parthian Empire in the winter of 165–166, and who carried the disease home in early 166. The earliest recorded case, however, is that of the orator Aelius Aristides, who nearly died of it at Smyrna in Asia Minor in 165. The disease reached Rome in 166 and had spread to almost every part of the empire by 172. Lucius Verus died in 169, possibly of the plague, and the outbreak lasted until about 180.

Galen saw the disease at first hand, including an outbreak among soldiers quartered at Aquileia during the winter of 168–169. He described fever, diarrhoea and inflammation of the throat, with a rash, sometimes dry and sometimes pustular, appearing around the ninth day. Scholars have long identified it as smallpox, though Galen's account does not fit perfectly and genetic research indicates that smallpox in its deadliest form reached in Europe much later. Measles has also been proposed, but molecular studies place its emergence after about AD 1000. No ancient genetic material from the epidemic has yet been identified.

Ancient writers describe huge losses. Eutropius says a large share of the population died, and Cassius Dio reports that a later outbreak in 189, perhaps a recurrence, killed up to 2,000 people a day in Rome. Modern estimates range from 2 to 33 percent of the population, between 1.5 and 25 million people, though most cluster around 10 percent, with higher rates in the cities and the army.

The plague coincided with the start of the Marcomannic Wars, when Germanic peoples crossed the middle Danube into Roman territory and pushed as far as Italy. Ancient writers say the army was almost wiped out, and Marcus Aurelius had to recruit gladiators, slaves and even bandits. He took the offensive in 169 and had expelled the invaders by 171, but fighting continued intermittently until his death in 180, possibly also from the plague.

Historians disagree about the plague's long-term importance. In the nineteenth century Barthold Georg Niebuhr saw it as a blow from which the ancient world never recovered, and Kyle Harper has recently placed it near the centre of Rome's story; other historians consider such views overstated. Archaeology suggests that Roman trade with India and South-East Asia through the ports of Egypt suffered a major setback. Recent research also links this epidemic, the Plague of Cyprian and the Plague of Justinian to periods of cooler, drier climate.

Our 200 map shows the Roman Empire at the end of the Antonine era, just after the plague, alongside its Parthian rival to the east, where Roman tradition placed the disease's origin.