Ancient accounts place the epidemic’s first appearance during Lucius Verus’ Parthian campaign, with an outbreak reported around the Roman siege/sack of Seleucia in the winter of 165–166. Later writers linked the wider imperial epidemic to troops returning west from this theater.
Modern medical-historical summaries describe the outbreak beginning in late 165/early 166 in Mesopotamia during Verus’ campaign and then spreading rapidly along military and travel routes toward Rome and other population centers.
By 166 the epidemic had reached Rome. The physician Galen is reported to have left the city during the outbreak, later becoming a key witness through his scattered descriptions of symptoms and course of illness.
Marcus Aurelius and Lucius Verus celebrated a joint triumph at Rome for the Parthian War in 166. The event occurred as the epidemic was taking hold in Italy, highlighting how military mobility and public mass gatherings coincided with disease spread.
Galen returned to the western imperial sphere in 168 when summoned by the co-emperors. His later notes became the most-cited clinical description of the Antonine Plague, including fever and a characteristic eruptive rash.
In the winter of 168/169, Galen observed a severe outbreak among troops stationed at Aquileia. This episode is often used to date a major wave of the epidemic affecting armies mobilized for frontier war.
After the Aquileia winter quarters and renewed sickness, Lucius Verus fell ill en route back to Rome and died in early 169. Ancient and modern narratives commonly treat his death as plausibly connected to the epidemic.
Facing heavy military costs during a period described as marked by “grievous pestilence,” Marcus Aurelius held a public auction of imperial furnishings (including luxury vessels and silken gold-embroidered garments) in Trajan’s Forum, a high-visibility fiscal response to compounded war-and-disease pressures.
The Antonine Plague is generally dated as a prolonged, multi-year epidemic (commonly 165–180) that strained manpower and finances during the Marcomannic Wars. Galen’s description—fever, gastrointestinal symptoms, and an eruptive rash—has often been interpreted as consistent with smallpox.
In spring 175, the eastern commander Avidius Cassius was declared emperor by his troops (reportedly amid false news of Marcus’ death). The episode illustrates how prolonged crisis conditions under Marcus Aurelius—including the aftershocks of epidemic and frontier war—coincided with heightened political instability.
Marcus Aurelius formally shared imperial power with his son Commodus in 177, making Commodus co-ruler. This succession planning took place while the empire was still recovering from years of epidemic disruption and ongoing military burdens.
Marcus Aurelius died on 17 March 180 while on campaign (sources place his death at Vindobona or near Sirmium). The commonly cited terminal date for the Antonine Plague is “about 180,” making his death a practical historical marker for the epidemic’s final major phase under the Antonine co-emperorship.
The Antonine Plague and Imperial Responses (165–180 CE)
