Near the end of his 680-page tome on the global history of disease, Kyle Harper at the University of Oklahoma poses the ultimate pandemic question: is Covid-19 “a painful lesson on our path to even greater control over microbial threats, or the harbinger of a new period in which our freedom from infectious disease becomes increasingly less secure?” Inevitably, he answers cryptically: it is too early to know. But for those who feel confident that the plagues and pestilences of past centuries are safely behind us, Harper’s new book, Plagues upon the Earth, provides a sobering call for caution. “Coronavirus did not appear out of the blue. It stands in a continuous line of emerging threats, and it follows an unbroken series of near misses,” he warns. While not making light of the remarkable progress we have made in containing the pestilences that have through 200,000-300,000 years of human history regularly culled populations, Harper warns that “humanity’s control over nature is necessarily incomplete and unstable … We do not, and cannot, live in a state of permanent victory over our germs.” Yes, the scientific progress that has over the past two centuries brought understanding of how we get infected, how to foster reliable treatments, how to develop disinfectants, and how to galvanise governments to invest massively in public hygiene and health care, has made us better equipped to control parasites and diseases. But, at the same time, human progress has created an environment where our microbial enemies can thrive: “Our exposure to the threat of new diseases has never been greater, simply because of our numbers,” says Harper. In short, humans have become an irresistible target for an unparalleled range of bacteria and viruses that depend uniquely on us and on the disequilibrium we have created in the “Anthropocene Age”. “What we think of as a medical triumph – the control of infectious disease – is from a planetary perspective a truly novel, systemic breakdown of an ecological buffer,” says Harper, marvelling at the “dizzying novelty of the current experiment in human supremacy”. The development of farming, cities and global travel has incubated and “weaponised” the pandemic potential of “crowd diseases” like tuberculosis, typhoid, dysentery, cholera, smallpox and malaria, in a way that would never have been possible even 2,000 years ago: “There were no crowds in the early Neolithic,” Harper notes: “Big city life, and big city death, were things of the future.” “As humans have spread to every niche on the planet, slashed and burned landscapes, settled into sedentary habitats, tamed a few favoured animals, learned to cross continents and oceans and constructed giant cities, we have changed the ecological prospects for our pathogens,” he argues, describing us as “a boom and bust species” that “spreads like a weed, lives like a rat, and consumes like a plague of locusts. In time, we have acquired the pathogen load to match.” Addressing those scientists who argue that we have developed the tools needed to keep infectious diseases permanently at bay, Harper reminds us that humans are crude novices in a microbial battle for survival that has been waged for aeons. The bacteria and viruses that exist today have survival strategies based on hundreds of millions of years of battles between hosts and parasites. By comparison, we humans have been around for just 10,000 generations, and for all but the past three or four, these have been brutish and short. Viruses aren’t just a threat, they’re essential to life on Earth “Evolution is relentless, and our invisible enemies are ceaselessly tinkering with new strategies to pass on their genes,” Harper notes. I recall the famously humorous Oxford biologist, Peter Medawar, called a virus “a piece of bad news wrapped up in protein”. For those who have been battling the coronavirus worldwide over the past two years, Harper’s marvellous tome teaches humility and brings both comfort and discomfort. Humility that no matter how astute and vigilant we may be, it is naive, even preposterous, to believe we will ever see the back of infectious diseases. Recurrence is inevitable, and our strategies going forward must acknowledge this at the outset. Comfort that the knowledge, clinical tools and health care institutions we have developed over the past two centuries have enabled us to mitigate a novel microbial attack that, until recently, would have wrought immeasurably more devastation across the world than it has. Discomfort that so many mistakes have been made in managing the virus, measured in the loss of millions of lives and in trillions of dollars of economic harm. Worst have been the failure to cooperate internationally and the cruel refusal to act on the self-interested imperative of the world’s rich economies to vaccinate communities across the poorest countries in the world. Harper inscrutably observes that the World Health Organization, which should sit at the heart of effective global response to any pandemic threat, has power and funding that is “anaemic relative to its vision and purpose”. Harper finally reminds us that while pandemic harm has, over the centuries, often been the result of poverty, famine and violence, it has also been the result of economic growth, population expansion and humankind’s sheer dynamic “exuberance”. 240 million reasons to end Covid-19 vaccine hoarding by the rich Our relentless encroachment on pristine habitats and the animals and microbes that inhabit them, our homogenising “domestication” of so many plants and animals, and our contribution to global warming carries grave dangers, and infinite new opportunities for new viruses to ruin all we have achieved. Harper reminds us that our responsibilities in the new Anthropocene Age are awesome and largely unrecognised. This Covid-19 pandemic reminds us that we custodians of the Anthropocene ignore those responsibilities at our peril. David Dodwell researches and writes about global, regional and Hong Kong challenges from a Hong Kong point of view