The Antonine Plague of 165–180 CE—also known as the Plague of Galen, who described it—was an ancient pandemic brought back to the Roman Empire by troops returning from campaigns in the Near East.
The plague began shortly after the1st Jewish Blood Moon lunar eclipses in 162 – 163 AD.
It has been suspected to have been either smallpox or measles, but the true cause remains undetermined. The epidemic may have claimed the life of Roman emperor Lucius Verus, who died in 169 and was the co-regent of Marcus Aurelius Antoninus, whose family name, Antoninus, was given to the epidemic. The disease broke out again nine years later, according to the Roman historian Dio Cassius, and caused up to 2,000 deaths a day in Rome, one quarter of those infected. Total deaths have been estimated at five million. The disease killed as much as one-third of the population in some areas and devastated the Roman army.
Ancient sources agree that the epidemic appeared first during the Roman siege ofSeleucia in the winter of 165–166. Ammianus Marcellinus reports that the plague spread to Gaul and the legions along the Rhine. Eutropius asserts that a large population died throughout the Empire.