I enjoyed the novel Good Omens and the recent eponymous TV miniseries. In it, the biblical Four Horsemen of the Apocalypse return to modern-day Britain. Although the Book of Revelations never actually says so, one of the Horseman is traditionally thought of as Pestilence. That is, infectious disease. However, authors Pratchett and Gaiman reasoned that germs have been largely defeated and make for a lame villain. So, they replaced Pestilence with Pollution. Unrelatedly, this XKCD comic also suggests that Pestilence has been slain, and nuclear weapons have taken up the saddle. This trope is increasingly common. The Horsemen, it is thought, require an update. We destroyed Pestilence with antibiotics and vaccines, right? Pestilence is downplayed, seen as obsolete, or just ignored.

I have two points in reaction. First, personifying Pestilence is actually a useful way to understand history. Pestilence has been the human adversary. The scoundrel has slaughtered far more people than all other causes combined, and sealed the fates of nations over the millennia. Yet we hardly ever tell this story as a story, with a concrete antagonist. Pestilence taps our body fluids like a vampire. Pestilence pulls the strings during key events on the world stage. Pestilence suffers our attacks, and bounces back. The bouncing back part is the basis for my second point. Pestilence isn’t dead. Pestilence has been shackled by modern medicine, but all of that work could still come undone. As the global population becomes denser and more interconnected, we become easy fodder for the next big plague. Only with constant vigilance do we retain the upper hand. And all of this makes for an epic drama. This war has been the main story of our species. Yet, bizarrely, it’s rarely told.

The major events in history have all been governed by disease. Smallpox. Flu. Tuberculosis. Malaria. Measles. Yellow fever. These have had a much bigger effect than any of the famous leaders or heroic battles that fill the bulk of most history books. Obviously microorganisms are mindless and without agency. But if we think of them as Pestilence upon a white steed, maybe they are harder to forget. Pestilence, the character, should dominate the social studies curriculum. There should be a Broadway musical about Pestilence. We should have an annual holiday where we share legends of the heroes who have fought Pestilence. The fingers of Pestilence already permeate our culture, but they’re hidden. For example, even before microbes were discovered, it was clear that contact with corpses leads to misfortune. This observation spawned our myths about ghosts and the taboos surrounding death. But, it was really Pestilence in the shadows all along. One thing Good Omens does well is that the Horsemen aren’t portrayed as frenzied warriors. Think of Pestilence as cunning and Machiavellian, strolling through the city gates without rousing alarm. Then, before you know it, Pestilence is running the show. Here are just a few examples how.

Human populations have always differed in susceptibility. This can occur because of evolved genetic immunity. Or, antibodies can simply build up in some people during a lifetime of living in an infectious environment. These differences influence who can subjugate whom. As laid out in Diamond’s Guns, Germs, and Steel, the main reason that Eurasians could conquer the Americas and Oceania was immunological. They were relatively resistant to the smallpox and other viruses that traveled with them, and indigenous peoples were not. In parallel, resistance to malaria allowed agricultural African populations to overtake the indigenous populations across that continent. When malaria spread to the western hemisphere, resistant Africans made the best laborers, sparking the horrific trans-Atlantic slave trade. In the 18th and 19th centuries, the wars among European thrones and their overseas colonies were largely decided by which armies could best withstand infection. These outcomes set up the borders of the modern geopolitical world. And immune systems still contribute to inequality today. For example, inborn resistance to HIV is most common in Europeans. That partially explains why AIDS has caused its worst devastation in Africa, Asia, and other non-white populations.

Even beyond these differences in resistance, the death toll from epidemics is often simply huge. It can thus have a massive impact on society. The Black Death in the 1300s probably killed over 100 million people, reducing the world’s population by a quarter. Just a century ago, the Spanish flu took out a similar number, though of course there were over a billion of us by then. Today, tuberculosis alone continues to cause over a million deaths every year. Societies stagnate or fail when reeling from disease. If they recover and beat Pestilence back, that’s when cultural innovations like the Renaissance happen.

Finally, even if you think history is determined by the actions of specific influential people, Pestilence still wins. That’s because many important historical figures died prematurely from disease. Who knows what would have happened otherwise? Alexander the Great died at 32 from infectious fever. Among English kings, Richard the Lionheart died at 41 of gangrene, while Edward VI died at 15 of tuberculosis. The loss of young heirs has also shifted power: Emperor Peter II of Russia died at 14 of smallpox and Napoleon II died at age 21 of tuberculosis. Native Americans Pocahontas and Squanto both saw Europe and were poised to be de facto intercontinental ambassadors, but got sick and died before middle age. Others didn’t die, but missed a chance to turn the tides while bedridden. Meanwhile, who can say how many would-be gamechangers were felled as children and are lost to time? And it still affects us. French philosopher Michel Foucault died of AIDS in 1984. Had he lived he could still be shaping current ideas as a 93-year-old today.

Why does all this matter, in the age of modern medicine? Because our victory over Pestilence is shaky. Bacteria can rapidly evolve resistance to antibiotics. If we misuse these drugs, they become useless and we return to the days of King Richard, when a flesh wound was deadly. Vaccines are only effective if we continue to apply them. The anti-vaccine movement is dangerous and threatens to unleash diseases that we had mostly gotten under control. And we don’t have shots for everything yet, certainly not whatever new epidemic is still over the horizon. Also, remedies are costly. Lethal infection remains a serious daily risk in many of the poorer regions of the world, where treatments are scarce. This is to say nothing of biological warfare or terrorism. Such deliberate actions are easier than ever with today’s molecular genetic technology. On top of it all, pathogens will thrive and spread with climate change.

I have a lot of faith in medical science. I don’t think it’s likely that I, or my middle-class American family, will die of infection. At least not before old age weakens us first. But, my confidence depends on society continuing to actively support the struggle against Pestilence. We need to use existing technology wisely, and continue to invest in new therapeutic strategies. It does no good to pretend that Pestilence is exterminated. Keep telling the story.