Antonin Plague, 165-180
The Antonin Plague, sometimes called the Plague of Galen, began in 165 CE. The plague reached Rome from the Near East, carried by marching Roman troops. Chinese records show the existence of plague around the same time, so this may have been related. It’s likely that the plagues in each region shared the same source. The plague spread along Roman roads, reaching Gaul or modern-day France, as well as other parts of Europe. The Roman Empire was quite connected, providing easy pathways for the spread of illness.
Based on the descriptions of the illness, the plague may have been smallpox or measles. Galen, in 168, describes the plague as involving fever, diarrhea, pharyngitis, and a rash, either dry or with pustules. Based on the timeline of the illness, smallpox, perhaps an unusually virulent variety, was the likely cause of the Antonin Plague. There were frequent recurrences of the same illness over the next 15 years.
Later writers suggested that many towns and villages lost their entire populations to the Antonin Plague. Within 15 years, the Antonin Plague had killed approximately 30 percent of the population of the Roman Empire. In the city of Rome alone, in 178, around 2000 people were dying each day. At least one Roman Emperor likely fell victim to the Antonin Plague. The Roman army, well-fed and supported by the standards of the time, lost one in every 10 soldiers, causing significant military weakness.
The Antonin Plague weakened not only the army, but also the economy and trade in the Roman Empire. As with later bouts of plague, religious fervor increased, and access to education and necessary services decreased in the face of a public health crisis. The Antonin Plague may have actively contributed to the weakening, and even the eventual fall, of the Roman Empire.