The success of the Five Good Emperors ironically brought about the worst plague in Rome’s epic history. Due to constant warfare on the borders and attempts to defend positions against various groups, Roman soldiers came into contact with foreign diseases, and they unwittingly brought them home when campaigns ended. This culminated around 165 CE, when an unidentified disease brought the empire to its knees and afflicted an untold number of individuals, one of whom may have been Lucius Verus, the co-emperor of Rome alongside Marcus Aurelius. 

In addition to the enormous number of casualties, which has been estimated at upwards of 5 million people, the pandemic disrupted Roman trade to the east, affected societies culturally across Europe, and compelled physicians like Galen to study the symptoms in an effort to figure out not only what the disease was, but any potential cures. Of course, that was a tall task for ancient doctors with relatively primitive technology, and even today people continue to debate what the disease was and where it came from, with theories ranging from a smallpox outbreak in China, or possibly measles. 

The Roman Empire and the Plague: The History of the Worst Pandemics to Strike Rome and the Byzantines in Antiquity and the Middle Ages charts the history of the diseases and how they shaped subsequent events, bringing down nations while inadvertently lifting others. It also describes the diseases’ victims, and how certain segments of society may have avoided contracting it.