Antonine Plague (165–180 CE)

Summary

In 165 CE, Roman soldiers returning from a war in the East brought a devastating disease back with them. It spread across the entire Roman Empire — from Syria to Rome and beyond — killing millions of people over the next fifteen years. The physician Galen was practicing in Rome when the plague arrived and later treated hundreds of victims, leaving behind the most detailed ancient account of the disease. Based on his descriptions of the symptoms — especially a black, ulcerated skin rash — most modern historians think the disease was smallpox, possibly the first time that infection had ever entered the Mediterranean world in epidemic form. The death toll may have reached five million people or more, with some areas losing a quarter of their population. The plague weakened the empire’s army, damaged its economy, and contributed to broader instability that persisted long after the epidemic ended.

Origins and Spread

The pandemic that would later bear the name “Antonine” — after the dynasty ruling Rome — originated in the East during Rome’s campaign against the Parthian kingdom. It reached Italy with the returning army of the co-emperor Lucius Verus.(Mattern, 2008) Galen, writing late in life, gave a compressed account of its arrival: “When the great plague began, I immediately left the city and traveled to my homeland.”(Mattern, 2013)

The disease did not wait for Rome. The plague struck the city of Smyrna in 165 CE, where it infected the household of the rhetorician Aelius Aristides, who barely survived.(Mattern, 2013) Nutton notes that the disease moved westward from Persia across the whole empire, carrying as far as beyond the Rhine and across the Channel.(Nutton, 2023) It was supposed at the time to have been carried initially by the victorious Roman army returning from its eastern campaign.(Nutton, 2023)

Galen’s own confrontation with the plague at full force came not in Rome but at Aquileia, in northern Italy. He had been summoned by imperial command in late 168 CE to join the emperors as they assembled for the German campaign. What he found there was catastrophic: “When I reached Aquileia, the plague descended as never before; so that the emperors immediately fled to Rome with a few soldiers, while most of us struggled for a long time to stay alive, and a great many died — not only because of the plague, but also because these things were happening in the middle of winter.”(Mattern, 2013)

Lucius Verus, the co-emperor, died of the plague in early 169 CE, leaving Marcus Aurelius as sole ruler for the extended German wars.(Mattern, 2013)

Galen’s Account

Galen’s writings are the primary surviving ancient source for the Antonine plague. His descriptions are scattered across several works — including On the Method of Healing, On Prognosis, and On Antidotes — rather than consolidated in a single epidemic report.

Galen described the characteristic rash in detail: black, often ulcerated eruptions “close together” over the whole body, which eventually formed scabs that fell away.(Mattern, 2013) He noted that the excretion of black diarrhea was another common feature. He interpreted these symptoms through humoral theory, viewing the plague as caused by an excessive accumulation of black bile; the rash and black diarrhea he considered hopeful signs — evidence that the body was expelling the toxic humor.(Mattern, 2013)

Mattern notes that his description of the rash as black and resembling “a deposit of ashes on the skin” suggests the late-forming variety of hemorrhagic smallpox — a rare, almost always fatal form.(Mattern, 2013)

On the question of how the plague spread, Galen is largely silent, except for one passage that attributes transmission to breathing corrupted air — the standard Hippocratic miasmatic explanation.(Mattern, 2013) He also invoked the precedent of Hippocrates, who had reportedly treated the great Athenian plague of 429 BCE by purifying the air with fires.(Mattern, 2013)

Galen treated hundreds of plague victims personally.(Mattern, 2013) His remedies included milk from Stabiae (near Pompeii), earth from Armenia, and the compound antidote theriac. He also acknowledged that a Syrian folk remedy — the urine of a boy — could work, however repulsive he found it.(Mattern, 2013) The plague was personal: Galen lost almost all of his slaves at Rome and his close friend Teuthras to the disease.(Mattern, 2013)

The Antonine plague also shaped Galen’s subsequent career in an indirect way. Galen fled Rome in the summer of 166 to avoid the plague, returned in 168–69, and late in life acknowledged the desire to escape the epidemic as one reason for his initial departure.(Nutton, 2023) Hankinson’s introduction to On the Therapeutic Method confirms this sequence: Galen fled Rome in 166, returned the following years, declined the German campaign citing Asclepius, and remained in Rome to treat Commodus.[galen-therm91-ch06-006] When Marcus Aurelius prepared to march north for the German campaigns, Galen invented an excuse to stay behind — claiming that the god Asclepius had appeared to him in a dream and forbidden him from going.(Mattern, 2013) He thus spent the following years in Italy treating the young Commodus and writing his most productive period of major works.(Mattern, 2013) Mattern also notes that by remaining in Italy, Galen missed a rare opportunity: army physicians on campaign were permitted to dissect slain barbarians, the only context in Roman society where human dissection was allowed.(Mattern, 2013)

The two external events that appear with most frequency in Galen’s case histories as temporal landmarks are the Antonine pandemic in the mid-160s and Marcus Aurelius’s departure for the Bohemian campaign in 168.(Mattern, 2008)

Medical Identification

The identity of the Antonine plague remains a matter of scholarly debate. Most modern scholars identify the 166 CE epidemic as smallpox, and Mattern estimates it may have killed as much as 30 percent of Rome’s population on first arrival, though the figure is uncertain.(Mattern, 2008) Modern scholars have most often identified it as smallpox, making it possibly the first epidemic of that disease to reach the Mediterranean region.(Mattern, 2013) Mattern is explicit that this identification is interpretive, not certain: “Few physicians practicing today have seen a case of smallpox, which was eradicated in 1977.”(Mattern, 2013)

Rosen’s History of Public Health is more cautious, listing three possible diagnoses that have been proposed based on contemporary accounts: exanthematic typhus, bubonic plague, or smallpox.(George Rosen, 1993) The plague is referred to in some sources as “the Long or Antonine pestilence,” running from 164 to 180 CE and ravaging the empire from Syria to the West.(George Rosen, 1993)

Mattern’s reading of Galen’s rash description — black, close-set eruptions resembling ash deposits on the skin — aligns best with hemorrhagic smallpox in the modern literature.(Mattern, 2013) Porter’s Greatest Benefit to Mankind follows this identification, calling it “probably smallpox which had smouldered in Africa or Asia before being brought back from the Near East by Roman troops.”(Porter, 1997) Porter adds that it killed “a quarter of the inhabitants in stricken areas” between 165 and 180 CE.(Porter, 1997)

Smallpox, as Porter notes in a broader context, derived from cattle — cattle providing “the pathogen pool with tuberculosis and viral poxes like smallpox” — and populations with no prior exposure would have had no immunity.(Porter, 1997) If the Antonine plague was indeed smallpox’s first visit to the Mediterranean world, a very high case fatality rate in a virgin population would be consistent with Galen’s grim account.

Demographic and Political Impact

The demographic consequences were severe. Nutton, drawing on Egyptian tax records, puts the population reduction at “perhaps 10–15 per cent, and in some places considerably more.”(Nutton, 2023) Mattern’s estimate is higher: approximately 25 percent of the Roman Empire’s population may have died in the pandemic — perhaps fifteen million people — with whole villages in Egypt effectively disappearing from the tax rolls, wiped out by a combination of mortality and the flight of survivors.(Mattern, 2013)

Porter offers a slightly lower figure of some five million total deaths, while still placing local mortality at “a quarter of the inhabitants in stricken areas.”(Porter, 1997)

Zinsser, writing in Rats, Lice and History, makes the broader argument that epidemics were a decisive and systematically neglected factor in Rome’s fall. He contends that maintaining an empire of Rome’s scale without modern sanitary knowledge was inherently unsustainable — the concentration of large urban populations, free communication with Africa and the East, and constant military mobilization “inevitably determine the outbreak of epidemic disease.”(Zinsser, 1935) Zinsser specifically notes that the disintegration of the Roman Empire resulted from complex causes, but that the role of repeated epidemic pestilences during Rome’s most turbulent political periods has been unduly overlooked.(Zinsser, 1935)

The Antonine plague did not operate in isolation. It was followed in the third century by the Plague of Cyprian (251 CE onward), which struck for nearly fifteen years precisely when the empire was experiencing its worst domestic disorders and foreign invasions.(Zinsser, 1935) Together, these successive waves of epidemic disease compounded the empire’s structural vulnerabilities.

Religious Response

The plague’s arrival prompted responses well beyond medicine. Nutton notes that when the Antonine plague reached Asia Minor in 165, many cities sent delegations to consult the great oracles at Claros and Didyma, seeking divine guidance.(Nutton, 2023) The snake-god Glycon at Abonuteichos distributed protective messages throughout the Roman Empire, warning of impending destruction by fire or plague, with brief guaranteed-safety inscriptions affixed to house doors.(Nutton, 2023)

Galen himself was a devoted worshipper of Asclepius, and credited the god with forbidding his participation in the German campaign — a divine excuse that allowed him to stay safely in Italy while the army returned to the plague-ravaged frontier.(Mattern, 2013) Nutton observes that it is incorrect to draw a simple dichotomy between rational medicine and religious healing in the ancient world: Galen, the era’s foremost physician, “was equally confident that his whole career had been guided by the god.”(Nutton, 2023)

Significance for Medical History

The Antonine plague holds several positions in the history of medicine. As a matter of source history, it produced the most detailed ancient clinical description of what is plausibly an epidemic disease. Galen’s account — however embedded in humoral theory — constitutes observational data that later historians have used to reconstruct the disease’s identity across nearly two millennia.(Mattern, 2013)

The epidemic also reshaped Galen’s own career and writing. By fleeing Rome at the plague’s onset in 166, then returning under imperial compulsion only to encounter it again at Aquileia, Galen accumulated clinical experience with plague victims at a scale few physicians would match. His decision to avoid the German campaigns — medically motivated by divine instruction, practically motivated by surviving the epidemic — gave him the years of protected productivity in which he wrote some of his most important works.(Mattern, 2013)

For the broader history of public health, the plague illustrates a structural problem that Roman infrastructure could not solve. The empire’s aqueducts, baths, and sewer systems — celebrated by Rosen as genuine public health achievements — offered no protection against a respiratory or contact-transmitted epidemic moving along military supply routes.(Zinsser, 1935) The Antonine plague demonstrates that premodern epidemic preparedness was essentially non-existent as a state function: Nutton notes that except among Jews and Christians, responsibility for health in antiquity was “a purely private matter for the individual and the individual’s family.”(Nutton, 2023)

Finally, the plague matters as a model for the role of disease in historical change. Zinsser’s argument — that epidemic pestilences were materially if not decisively influential in Rome’s final outcome — found support in later historiography. McNeill’s framework of “virgin soil” epidemics entering immunologically naive populations offers a plausible mechanism for explaining why this particular epidemic, if it was indeed smallpox arriving in a Mediterranean world that had not previously encountered it, should have been so catastrophic.(Porter, 1997)

See Also

• galen — Primary ancient source; physician who treated plague victims and described its symptoms
• marcus-aurelius — Emperor during the plague; suffered its political and military consequences
• lucius-verus — Co-emperor; probably died of the plague in 169 CE
• plague-of-athens — Earlier epidemic (430 BCE) that Galen referenced as a precedent
• plague-of-cyprian — Subsequent epidemic (251 CE) that continued weakening the empire
• theriac — Compound antidote that Galen used in plague treatment
• humoral-theory — Framework within which Galen interpreted the plague’s mechanism

Sources