The Antonine Plague (also known as the Plague of Galen, who described it), was an ancient pandemic, of either smallpox or measles, brought back to the Roman Empire by troops returning from campaigns in the Near East.
The epidemic claimed the lives of two Roman emperors — Lucius Verus, who died in 169, and his co-regent who ruled until 180, 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 at 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 decimated the Roman army. The epidemic had drastic social and political effects throughout the Roman Empire, particularly in literature and art. (Pictured above is a plague pit containing the remains of people who died in the Antonine Plague.)