Antonine Plague

The Antonine Plague of AD 165 to 180, also known as the Plague of Galen (after Galen, the Greek physician who described it), was a prolonged and destructive epidemic, which impacted the Roman Empire. It was possibly contracted and spread by soldiers who were returning from campaign in the Near East. Scholars generally believe the plague was smallpox, although measles has also been suggested, and recent genetic evidence strongly suggests that the most severe form smallpox only arose in Europe much later. In AD 169 the plague may have claimed the life of the Roman emperor Lucius Verus, who was co-regnant with Marcus Aurelius. These two emperors had risen to the throne by virtue of being adopted by the previous emperor, Antoninus Pius, and as a result, their family name, Antoninus, has become associated with the pandemic.

Ancient sources agree that the plague is likely to have appeared during the Roman siege of the Mesopotamian city of Seleucia in the winter of 165–166, during the Parthian campaign of Lucius Verus. Ammianus Marcellinus reported that the plague spread to Gaul and to the legions along the Rhine. Eutropius stated that a large proportion of the empire's population died from this outbreak. According to the contemporary Roman historian Cassius Dio, the disease broke out again 9 years later in 189 AD and caused up to 2,000 deaths a day in the city of Rome, 25% of those who were affected. The total death count has been estimated at 5–10 million, roughly 10% of the population of the empire. The disease was particularly deadly in the cities and in the Roman army.

The Antonine plague occurred during the last years of what is called the Pax Romana, the high point in the influence, territorial control, and population of the Roman Empire. Historians differ in their opinions of the impact of the plague on the empire in the increasingly troubled eras after its appearance. Historians have noted similar plagues in the Han Empire of China during the mid-to-late 2nd century AD that caused devastating effects there, at a time when ancient Chinese historians claimed diplomatic contacts were made with what they perceived to be the Roman Empire. Based on archaeological records, Roman commercial activity in the Indian Ocean extending to the Indian subcontinent and Southeast Asia from ports of Roman Egypt seems to have suffered a major setback after the plague.