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165-180 CEReputable source · 2 sourcesDebated

The Antonine Plague Follows Roman Legions Home

A disease carried back from the Near East by Roman soldiers kills up to 2,000 people a day at its peak and helps end the empire's golden age

On the timeline · around 165-180 CE · Ancient PlaguesAncient PlaguesMedieval PandemicsThe Antonine Plague Follows Roman Legions Home100 BCE1 CE100 CE200 CE300 CE400 CE500 CE

Quick facts

Pathogen
Likely smallpox or measles, based on Galen's description; not confirmed by ancient DNA
Also known as
The Plague of Galen
Duration
165 to 180 CE
Peak reported toll
Up to 2,000 deaths per day in Rome at its height
Origin
Brought west by troops returning from the siege of Seleucia

What happened

Roman troops besieging the city of Seleucia on the Tigris in 165 CE brought a new disease back with them, and it spread north and west along military supply lines to Gaul and the Rhine frontier. The Greek physician Galen, who treated cases in Rome and left the fullest surviving account, described fever, diarrhea, vomiting, an inflamed throat, and a skin eruption that appeared around the ninth day of illness, a symptom pattern that has led most modern researchers to conclude the disease was smallpox, though measles remains a competing candidate. Roman citizens had no prior exposure to either virus, so the outbreak moved through a fully susceptible population for fifteen years, killing at a rate estimated at up to 2,000 people daily in Rome at its worst.

Why it matters

The plague thinned the Roman army during Marcus Aurelius's wars on the northern frontier and disrupted the tax base and grain supply that funded them, contributing to the economic and military strain historians point to when explaining the end of the Pax Romana. It also set a pattern that would repeat: a crowd disease moving along a road or supply line built for something else entirely, in this case, imperial conquest.

How we know

Galen's clinical writings are the primary medical source; Cassius Dio's Roman History and other period authors supply mortality anecdotes, though ancient death tolls of this kind cannot be independently verified and should be read as scale indicators rather than precise counts.

Sources

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