In 1879 Jules Verne published a science fiction novel, The Begum’s Millions. In the story, two rival heirs—a French doctor and a German chemist—fall into a fortune left by a long-lost relative. They each use their share of the inheritance to build model cities far in the American West.

The contrasts are not subtle. The German establishes “Steel-City,” a nightmarish industrial town dedicated to the manufacture of destructive weapons. The doctor, by contrast, founds a city called “France-ville,” premised from top to bottom on scientific principles of hygiene, where public spaces and private habits are minutely regulated to promote healthy living: “To clean, clean ceaselessly, to destroy as soon as they are formed those miasmas which constantly emanate from a human collective, such is the primary job of the central government.” Citizens are indoctrinated from childhood “with such a rigorous sense of cleanliness that they consider a spot on their simple clothes as a dishonor.” Hygiene is a public imperative and private duty. In exchange for uncompromising vigilance, the residents of France-ville enjoyed the blessings of long life.

Verne’s story is a fable of modern science; it envisions a future in which human ingenuity is used to destroy or to preserve life. In the novel’s happy ending, Steel-City destroys itself, but there is something unsettling about France-ville, too: life is consumed in the crusade against disease and death. Such visions were in the air when Verne wrote; he cribbed the sanitary rules of France-ville almost verbatim from a contemporary British reformer named Benjamin Ward Richardson. In a speech delivered in 1876, Richardson imagined a utopia that he called Hygeia, the City of Health. For Richardson there was nothing inherently fictional about this future. “The details of the city exist,” he said. “They have been worked out by those pioneers of sanitary science.” In the coming years, he hoped the “desires and aspirations” of the hygienic reformers would become the lived reality of the mass of humanity.

Today many of us live in a version of Hygeia. Around 1870, even in the most rapidly developing nations, infectious disease still filled the graveyards. But soon human societies brought infectious disease under control. Toward the end of the nineteenth century, in the United States and Britain, a great threshold was crossed for the first time in the history of our species: noninfectious causes of death—cancer, cardiovascular disorders, and other chronic and degenerative diseases—accounted for a greater portion of total mortality than did infectious diseases. By 1915 an American social reformer could observe that “a generation ago we could only vainly mourn” the deaths of children from disease: “To-day we know that every dying child accuses the community. For knowledge is available for keeping alive and well so nearly all, that we may justly be said to sin in the light of the new day when we let any die.” By midcentury, dying of infectious disease had become anomalous, virtually scandalous, in the developed world.

The control of infectious disease is one of the unambiguously great accomplishments of our species. Through a succession of overlapping and mutually reinforcing innovations at several scales—from public health reforms and the so-called hygiene revolution, to chemical controls and biomedical interventions like antibiotics, vaccines, and improvements to patient care—humans have learned to make the environments we inhabit unfit for microbes that cause us harm. This transformation has prevented immeasurable bodily pain and allowed billions of humans the chance to reach their full potential. It has relieved countless parents from the anguish of burying their children. It has remade our basic assumptions about life and death. Scholars have found plenty of candidates for what made us “modern” (railroads, telephones, science, Shakespeare), but the control of our microbial adversaries is as compelling as any of them. The mastery of microbes is so elemental and so intimately bound up with the other features of modernity—economic growth, mass education, the empowerment of women—that it is hard to imagine a counterfactual path to the modern world in which we lack a basic level of control over our germs. Modernity and pestilence are mutually exclusive; the COVID-19 pandemic only underscores their incompatibility.

But to grasp the full significance of the history of infectious disease, we need more than ever to understand this recent success through the lens of ecology and evolution. Modern human expansion is unnatural in its scale. Global population in 1900 was 1.6 billion; in 2020, humans numbered 7.8 billion. The primary and proximate reason the human population has ballooned is the control of infectious disease. As Peter Adamson noted in the New Internationalist in 1974, human beings have multiplied deliriously not because we “suddenly started breeding like rabbits. It’s just that we’ve stopped dying like flies.” The rapid development and diffusion of disease control technologies thus helped to provoke what is known as the Great Acceleration, the startling intensification of human impact on the planet from the middle of the twentieth century. Our indelible impact has led many earth scientists and others to propose that we now live in the Anthropocene, a geological epoch defined by humanity’s pervasive imprint on the planet. The Anthropocene has a microbiological dimension too, as microbes respond and adapt to the human-dominated Earth.

Indeed, as human control of the environment has expanded, Darwinian evolution has continued, or even accelerated. The evolution of new pathogens is not an anomaly but rather the strictest obedience to the laws of nature. COVID-19 was the evolutionary product of the ecological conditions we have created—our numbers, density, and connectivity, especially in the age of jet travel. The ongoing pandemic has been a jarring reminder that humanity’s control over nature is necessarily incomplete and unstable. We urgently need to learn from the experience of this pandemic—and the larger history of the globalization of health over the twentieth century—to ready ourselves for the inevitable next one.