He was a child of privilege turned demagogue, a man who blurred the boundaries of politics and spectacle and seemed to think himself a divinity beyond mortal rules. His tumultuous tenure lasted longer than anyone expected. Then along came a pestilence that seemed a sordid reflection of the ruler’s arrogance and ineptitude. The disease revealed social tensions that had festered under the surface and brought back whispers of civil war. The people could stand no more, and even the faint-hearted Senate at last showed hopeful signs of courage.

With the scoundrel gone, power was entrusted to a senior senator whose respect for decency had come to seem like the most reassuring virtue. The ship of state was now to be steered by a safe pair of hands. I am talking, of course, about the Roman emperor Commodus and his successor Pertinax. Son of the emperor Marcus Aurelius, Commodus ruled as sole emperor for 12 years (A.D. 180-192), his reign marred by perpetual scandal. The emperor had disturbingly little esteem for traditional decorum. To the delight of some and dismay of many, Commodus participated in the gladiatorial spectacles himself. We can only imagine what he would have done with Twitter.

So when a vicious pestilence reappeared with tremendous ferocity — at its peak, it was said to have killed as many as 2,000 Romans a day — the tensions boiled hotter. In the words of one contemporary senator, Commodus himself was a curse worse than any plague. The unseemly emperor was finally strangled in his bath by a wrestler, Narcissus, at the urging of a group of conspirators. Drawing parallels between ourselves and the Romans is a favourite parlour game of history buffs, though among professional historians, it can seem a bit uncouth to tap into our training to treat Rome as a mirror of our own times. But there is a serious side to these parallels, too: The way we understand the past inevitably shapes how we understand the present. What we can learn from reflecting on this chapter of ancient Rome is not so much an example to follow or neatly packaged solutions for our own crises, but a different sensibility, an awareness of what a powerful force nature has been throughout human history. The pestilence under Commodus was part of a pandemic known as the Antonine Plague. It first appeared during the reign of Commodus’ father, Marcus Aurelius. It was not the plague, in the sense of bubonic plague, a distinctly horrific disease that would appear in the later stages of Roman history.

Which microbe was responsible for the Antonine Plague remains unclear, though most specialists believe that the likeliest culprit is an ancestor of the smallpox virus. The smallpox virus is less than 2,000 years old. The Antonine Plague may well represent an early stage of its evolution as a human pathogen. Like many viruses, the agent of smallpox belongs to a family many of whose representatives infect small mammals, like rodents. As human societies expand, and become more interconnected, we collide with animals and their diseases. Evolution relentlessly experiments with adaptations to new hosts, and some of these experiments unfortunately prove successful.

The Antonine Plague might have been one of history’s first “pandemics,” if by that term we mean an explosive disease outbreak on an intercontinental scale. Living through a pandemic not only causes us to see different layers of the past, but can also inspire us to listen to our ancient sources more empathetically.

Retracing the role that nature played in Rome’s history reminds us that we, too, are ecologically fragile, the fate of our society only partly under our control. A sense of our fragility should not make us fatalistic. Rather, it should inspire us to be less complacent. Even with all the tools of modern biological science, we could not have predicted exactly when and where a new pandemic would emerge. But we were warned, and those warnings went unheeded, in part because we told stories about ourselves implying that we had been freed from nature, that we were immune from the patterns of the past. It is a lesson we would do well to heed. The Antonine Plague wasn’t the last lethal pandemic the Romans faced. And Covid-19 won’t be ours.