In combatting Covid-19, scientists, public health experts and government agencies have occasionally turned to history for counsel. Measures taken, for better or worse, during the Spanish flu of 1918, which infected nearly a third of the world’s population, have been particularly influential in the formulation of healthcare policies. No less salutary, oddly, has been guidance from the Middle Ages, an era normally associated with religious mysticism and benighted superstition at the expense of medical science. For upon the advent of the bubonic plague in the 1300s—the notorious Black Death—epidemics began to ravage large parts of Europe, afflicting seaports in the Mediterranean following the arrival of infected ships and their crews from Asia. “The truth is, our most urgent modern biologic threats have required us to roll back to our fourteenth-century tool kit,” according to Martin Cetron, Director for the Division of Global Migration and Quarantine at the Centers for Disease Control and Prevention. Medieval measures included a primitive form of contact tracing, health passports and beaked masks stuffed with medicinal herbs and spices for the purported protection of plague doctors. More important, quarantines, the most effective remedy seven centuries ago, were rapidly implemented to try to curb the current pandemic. Already by April 2020, over 20 percent of the world’s population had been quarantined in some fashion, either locked-down or self-isolated. At first glance, Geoff Manaugh and Nicola Twilley would seem unlikely authors of “Until Proven Safe: The History and Future of Quarantine” (MCD, 396 pages, $28). Neither boasts credentials as a historian or a scientist. What instead makes their book compelling, besides their extensive experience as journalists, is the depth of their research coupled with a firm conviction that quarantine, a mighty yet dangerous weapon, must be used “more wisely in the future.” The actual purpose of a quarantine has always been, not to sequester diseased individuals indefinitely—as in the case of leper colonies and tuberculosis sanatoriums—but to detain persons whose exposure to a communicable disease was uncertain to evaluate their health. This turns on its head traditional Anglo-Saxon law, in which a person charged with a crime is innocent until proven guilty; under quarantine, internment rests upon a presumption of uncertainty. The first official quarantine for which written evidence has survived appears to have been instituted in 1377 by the port of Dubrovnik on the Adriatic Sea, in what is now southern Croatia. Public regulations forbade entry for a month to “those who come from plague infested areas.” Yet it was Venice, a crossroads of maritime trade that had lost some two-thirds of its population to plague in the 1300s, that in 1423 constructed the first lazaretto—a large stone building designed to confine potentially infected individuals. (The term “lazaretto” originated from several sources, including the Biblical beggar Lazarus, the patron saint of lepers.) Years afterward, Venice acquired a second structure—each was located on its own island—where food, water, and medical care were dispensed “for the public good.” By the early 18th century, such “quarantine hospitals” in Mediterranean Europe had become commonplace owing to the addition of monasteries, abandoned barracks and moored merchant ships. One of the most fascinating chapters in this enlightening book recounts the tireless efforts of the Englishman John Howard, an eccentric social reformer of ample wealth and unfailing courage, whose achievements on behalf of incarcerated criminals and debtors gave way by his late 50s to a newfound concern over conditions within quarantine facilities. In 1785, he embarked from London upon a far-flung journey across Europe to inspect a number of lazarettos—a mission that the authors, who traveled as far as Malta, endeavored to duplicate. Howard’s terminus was Constantinople, but a subsequent expedition took him to Ukraine, where he successfully persuaded the potentially typhus-infected inhabitants of Kherson to move to what came to be called Quarantine Island in the Dnieper River, shortly before Howard himself perished from the disease. Long afterwards, local residents, reported a Soviet magazine in 1945, still recalled “the Englishman who came from far off to help” their ancestors “in time of their distress.” Early 20th century quarantine sign for the contagious disease diphtheria. Photo: Everett Collection/Bridgeman Images Over the centuries not only people, but mail also was quarantined. Paper and other “soft materials”—among them cloth, wool and produce—were thought susceptible to infection. Letters, we are told, were doused with vinegar, grilled atop iron grates or even suspended by tongs over fire—leaving in many instances “scorch marks, stains, and incisions” that in combination with cancelled stamps have left modern experts with a “postal paper trail” indicating the course and timing of epidemics and the disinfection stations accompanying them, many of which would otherwise be “lost to history.” Besides coastal facilities, Europeans created cordons sanitaires between countries to enforce quarantines. Beginning in 1770, Austro-Hungarian officials, for instance, established a broad buffer zone that ran from the Adriatic to the Transylvanian Mountains. Scarcely an iron curtain, it was nonetheless enforced by 2,000 guard posts manned by armed peasants, “each no more than a musket-shot’s distance from the next.” Nineteen checkpoints permitted travelers to cross after being quarantined and properly inspected. “The cordon,” Ms. Twilley and Mr. Manaugh write, “served as both military and public health defense, protecting Europe from Oriental incursions of all sorts.” The zones that abutted this and other cordons spawned a liminal culture in which the human denizens reputedly suffered from “wall disease,” characterized not only by feelings of isolation but also high levels of depression, poverty and, not surprisingly, suspicion. The informality of the authors’ engaging prose, bearing few scholarly trappings save for the source notes, more aptly resembles that of an article in the New Yorker, where, in fact, portions of the book first appeared. Absorbing chapters, for instance, are devoted to modern containment measures and research centers designed with future perils in mind. While rigorous bans prohibit the importation of suspect produce and animals into most countries, a small number of facilities—such as the International Cocoa Quarantine Centre just west of London—exist for plants of high value that might be contaminated with pests and pathogens. Less conventional protocols exist for confining extraterrestrial matter, notwithstanding “the vast astronomical distances,” to quote C.S. Lewis, “which are God’s quarantine regulations.” Thanks to NASA and other space agencies, those distances have begun to shrink. And not just moonrocks have raised concerns. When the astronauts aboard Apollo 11 returned from the Moon to Earth on July 24, 1969, they remained in quarantine for three weeks. If not for the book’s arresting insights, undergirded by archival research and interviews with historians, epidemiologists and public health experts, “Until Proven Safe” might resemble at times a travelogue of misery, taking readers from one ill-starred site of disease and devastation to another, including recent outbreaks in central Africa and China. Along the way, we are exposed in frightening detail to such apocalyptic epidemics as cholera, yellow fever and Ebola (this is by no means an exhaustive list). Notwithstanding the untold suffering that Covid-19 has wrought, its horrific effects on the human body, readers are reminded, are not wanting for precedents. For a measure of relief from such unremitting sorrow, the authors might be forgiven a bit of melodrama in tracing their travels, not least having to surmount physical as well as bureaucratic obstacles, including the weed-infested ruins of crumbling lazarettos, and, to get a closer look, being forced at times to crawl, climb, and squeeze their way through narrow passages. Still and all, this is an exceptionally powerful book. The hard reality is that future epidemics of disease, given their certainty, pose a formidable threat to human life and that quarantines, however antiquated the practice, will often remain “our only defense”—our primary means to slow the spread of a disease long enough to develop a vaccine or cure. The ability of bacteria and viruses to proliferate across the world will continue to accelerate due to air travel and the ever-increasing volume of global trade. What’s more, the continual penetration of once-remote environments containing wild animals threatens exposure to thousands of new and potentially deadly pathogens capable of jumping hosts. Not that the authors ignore the perils that quarantines themselves pose. Quite the contrary. As history has shown, they have been used by nations to redraw the borders of contested territories, by corporations to gain mineral rights and by nativists to persecute immigrants. The current pandemic demonstrates that quarantines can be deeply problematic for ethical, legal and economic reasons, quite apart from the petty nuisance of wearing a mask. One does not need to be a disciple of French theorist Michel Foucault to anticipate that governments, if given the opportunity, are capable of expanding powers of regulation, surveillance and confinement in the name of safeguarding public welfare. The authors envision the dire possibility of a world, imperiled by disease, in which “smart homes” under quarantine will be equipped with “frontline emergency healthcare technology” maintained by a corporation—“temporarily imprisoning you for the public good—and for private profit.” What can be done? In this age of globalization, toughened border restrictions seem one obvious, if impolitic, step. But the solution that Ms. Twilley and Mr. Manaugh urge lies chiefly in advancing other common-sense measures, some already embodied in Covid-19 protocols, from social distancing to enhanced technology, including contact-tracing and contagion-modeling. Greater attention within quarantined zones needs to be given to plumbing networks, ventilation systems and waste disposal. But just as critical are actions required of authorities to create public trust as well as encourage a greater sense of personal responsibility, among them guarantees of financial, legal and medical support for those whose lives have been paused for the public good. “If public health authorities,” write the authors, “ask us to temporarily give up our freedom of movement, then they will also assume a duty of care, as well as assuring us due process.” Otherwise, as CDC official Martin Cetron points out, “When the trust account is bankrupt, you’re screwed.” —Mr. Ekirch is a professor of history at Virginia Tech and the author, most recently, of “La grande transformation du sommeil: comment la révolution industrielle a bouleversé nos nuits.”