The Plague Cycle: The Unending War Between Humanity and Infectious Disease, by Charles Kenny

Plague epidemic, ancient book illustration. Banner image: Shutterstock/ matrioshka
The Plague Cycle: The Unending War Between Humanity and Infectious Disease, by Charles Kenny

This extract from The Plague Cycle: The Unending War between Humanity and Infectious Disease by Charles Kenny (Published by Simon & Schuster, Inc., 2021), is part of a series in which OECD experts and thought leaders — from around the world and all parts of society — address the COVID-19 crisis, discussing and developing solutions now and for the future. Aiming to foster the fruitful exchange of expertise and perspectives across fields to help us rise to this critical challenge, opinions expressed do not necessarily represent the views of the OECD.

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The two leading killers worldwide at the start of the twenty-first century are heart attacks and strokes. That is evidence of humanity’s greatest triumph: until recent decades, most people didn’t live long enough to die of heart failure. Rather, they were felled by a range of infectious diseases that picked off the young or swept through whole populations in pandemic catastrophe. Covid-19 is a terrible reminder that our victory against infection is far from complete—and in all likelihood never will be complete. The cycle of population growth, pandemic, and recovery isn’t nearly as violent as it has been in the past, but it’s still with us.

For most of the time civilization has existed, pestilence has wiped out far more lives than famine and violence combined—so much so that Malthus’s proposed final limit of land and resources as the check to human numbers has rarely been approached. Disease has usually kept populations below the levels that could have been supported given agricultural technologies at the time. The expansion of civilization—and, in particular, of cities—was limited by the very diseases it had enabled. The rise and spread of civilizations, and the growing trade between them, provided parasites with unprecedented reach. As empires rose in Europe and China, and were linked by trade across the Asian steppe, new populations were exposed to diseases. Plague twice brought low much of Eurasia.

When Europeans discovered the New World, so did their pathogens. Great empires in the Americas were shattered thanks in considerable part to the onslaught of Old-World diseases that arrived with Columbus or those who followed him. When Africans were brought in to replace native populations as slaves, they carried with them some of humanity’s oldest infections, including deadlier strains of malaria. The indigenous population of the New World fell to less than one-tenth of its level of 1491 as a result.  But if globalization was a vehicle for the launch of pandemics, it’s also true that it was severely limited by the very same diseases. Conquest, colonization, and trade were all severely curtailed by the death rates faced by imperial adventurers in alien disease environments.

By the time of the last great die-offs of populations previously unexposed to Eurasian disease, the world was [however] on the verge of dramatic progress against infection. Global efforts against infection over the past two centuries— from washing hands to constructing sewer systems to making use of penicillin, immunization, and bed nets—have saved billions from premature death and billions more from stunted growth, pain, paralysis, blindness, or a lifetime of recurring fever. Two hundred years ago, almost half of all people born died before their fifth birthday, mostly from infection. Today, that figure is below one in twenty-five.

Millions still die every year of easily prevented or cured conditions, but the Malthusian trap has been sprung. The question remains as to whether it will stay open. If victories against infection have allowed us to get closer, to live with millions and travel worldwide, the coronavirus lockdowns and social distancing are a painful illustration of the psychological, social, and economic costs when we’re pushed apart again by a renewed threat of disease. That’s the irony of our progress against death from infection over the past two centuries. It has helped create the perfect environment for the emergence of a new disease outbreak and the perfect environment for that outbreak to have catastrophic social and economic impact.

More on the Forum Network: Is It Tomorrow Yet: Paradoxes of the Pandemic, by Ivan Krastev, Centre for Liberal Strategies

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The world’s population (human and livestock alike) has never been as large, nor commerce so global, nor peace so widespread. At the same time, we’re abusing our most effective tools against disease—misusing antibiotics by feeding them to farm animals in bulk; leaving our children unvaccinated; funding research on new bioweapons while underfunding new vaccines, treatments, and cures; and letting weak medical systems fester in the world’s poorest countries. And our reaction to disease too often echoes that of our distant forebears; at a time when global human interaction is central to our wealth and welfare, we call for flight bans and trade restrictions. Globally, we respond to new infectious threats too late. We don’t prepare and we don’t coordinate.

Covid-19 is only the latest in a succession of new infections that have emerged and spread in our closer and connected world. We have to do better for next time, because there will be a next time. Phenomena ranging from evolution to climate to demographics mean that many infectious diseases tend to follow cycles. After a first transition toward greater disease threats sparked by the rise of farming, followed by a second transition toward reduced threat thanks to interventions including sanitation, vaccines, and antibiotics, we’re now in a third epidemiological transition back toward greater infectious risk as a result of emerging new diseases spread worldwide by globalization.

This last idea likely underestimates humanity’s ability to respond to disease threats. We are flattening the plague cycle. But through sufficient neglect or miscalculation, we could allow communicable diseases to fight back and reclaim their place as death’s most popular weapon. History suggests such a reversal would shape the coming century more than almost any other conceivable event. And even if that full threat doesn’t materialize, we could allow poor response to new diseases like Covid-19 to stifle global progress. But at least recent history suggests humanity’s response to the new threat can be rapid and effective if we so choose.

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In 2017, about 10 million people died from communicable diseases worldwide. Many of those deaths were preventable. We need to extend the full benefits of the sanitation and medical revolution. And we need to improve our response to new disease threats. Both efforts will necessarily be global. Just as no one individual or family can fully respond to the infectious threat, in a globalized world neither can any one country.

Controlling the risk of new infectious outbreaks and pandemics is first and foremost about getting public health systems to work. It is in everyone’s interest that every country can provide at least the bare minimum of health coverage and epidemic preparedness. Beyond the health sector, the more that basic sanitation systems function, the less people will need treatments and cures in the first place. The World Bank estimates that it would cost $28 billion a year between now and 2030 to reach universal global access to basic water, sanitation, and hygiene facilities. That’s a lot of money (and, again, it will take more than money). On the other hand, given the global burden of disease related to poor sanitation, it might seem like a bargain.

The world’s governments also need to work together to eradicate some of the worst infectious threats, including polio, measles, and malaria. Such efforts are some of the highest-return investments we can make. The world’s governments should also come together to fund research toward new vaccines, antimicrobials, and vector control. If we want to reduce the risk of a global breakout by a disease customarily found in a developing country, the best response is proactive research and development, and that’s going to take global cooperation.

In addition, the world as a whole needs the spare capacity in pharmaceutical manufacturing to quickly scale up vaccine production. Not least, that involves retooling factories in advance of knowing precisely which vaccines will prove effective. The medical and sanitary advances that took place in the twentieth century transformed the world. There’s no reason that such advances should stop in the twenty-first. The planet has never been richer—able to afford more research and better disease response. At a cost simply dwarfed by the benefits we can resume our global progress against infection.

Worldwide, attempts to limit the coronavirus’s spread by reducing contact were unprecedented in scale. That cost could have been reduced, and, more important, lives could have been saved, if countries had been better prepared. For future outbreaks, governments should expand their stockpiles of masks, basic medical equipment, and drugs. And given that countries that tested many of their citizens early have seen fewer cases and less disruption, every nation should be creating the infrastructure and gathering the equipment to roll out testing, tracing, and isolation.

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From their experiences with Covid-19 governments should also learn what level of isolation is sustainable and for how long. One thing that determines how long and how much people can remain distanced is how long they can afford to do so. Providing financial support to ensure those who don’t need to go to work don’t have to, and providing protective equipment and training to the rest, is a tool both to reduce the economic impact of infection and to save lives. Thinking through financial mechanisms to equitably cushion the cost of lockdowns is a vital part of pandemic preparation.

The extent of disease has always shaped economic and social relations. Pandemics from centuries ago still help determine wealth and poverty, democracy and autocracy to this day. But the last half century clearly demonstrates that not all trends are inexorable. The tragedy of Covid-19 helps illustrate the utterly different world we’ve become used to living in.

If we continue on the path away from Malthusian doom, which we know how to do, how will the world appear different? With declining birth rates and longer lives, it will undoubtedly be older—but the changes go beyond that. Given the links between infection risk and xenophobia born in prehistory, a less infectious world will be friendlier, more cooperative, and less violent. And given the close link between the rise of infection and the subjugation of women at the dawn of civilization, perhaps it will be more equal. If the pandemic tragedies on the scale of Justinian’s plague, the Black Death, and the Atlantic disease exchange go unrepeated, it will be more stable. As good health boosts productivity, countries will be richer and more urbanized—and the gap between industrial and developing countries should continue to shrink. It won’t be a perfect world, but it will continue getting better.

Or perhaps Covid-19 is only a foretaste of even worse to come. Perhaps we’ll backslide. If anti-vaccine prophets peddle their deadly disinformation without response, if our last antibiotics are wasted on adding a few ounces of white meat to a chicken breast, if we do nothing to improve global cooperation, surveillance coverage, and rapid response to outbreaks, we know what the world will look like. A planet without our most effective tools against infection is one moving back toward Malthusian misery. It’s a world where our view of mortality as an increasingly private affair is blown away by mass burial of the young. It’s a world that is poorer, more violent, more insular—a bigoted and misogynistic place.

The history of infection teaches a particular lesson to those who want to withdraw from international cooperation: if disease becomes the excuse for closing borders and deploying force, the costs to global progress will be immense. We don’t have to accept a new pathogen as the will of God—nor are flight, fortresses, or imprisonment our only defense against the scourge. Because, for all of the failings and unnecessary deaths of the response to Covid-19, our scientific advances, our health institutions, and global cooperation have put us in an immeasurably better place to fight it than where Petrarch stood with the plague or Montezuma with smallpox.

Covid-19 temporarily and tragically reversed progress against infection. But still, far fewer parents than ever before in history go through the pain of burying their own children. The massive decline in premature death is something we should celebrate and protect as humanity’s greatest triumph.

Excerpted from The plague Cycle: The Unending War Between Humanity and Infectious Disease by Charles Kenny. Copyright © 2021 by Charles Kenny with permission by Scribner, a division of Simon & Schuster, Inc.

Excerpted from The plague Cycle: The Unending War Between Humanity and Infectious Disease by Charles Kenny. Copyright © 2021 by Charles Kenny with permission by Scribner, a division of Simon & Schuster, Inc.

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