People are beginning to understand there is nothing in the world so remote that it can’t impact you as a person. It’s not just diseases. Economists are now beginning to say if we are going to have good markets in Africa, we’re going to have to have healthy people in Africa.
—WILLIAM FOEGE, MD
For most of human history, infectious disease outbreaks weren’t much of a concern compared with the other challenges of staying alive and finding enough to eat. When our ancestors lived in small groups of hunters and gatherers, there wasn’t enough of a population concentration to create much of an epidemic. But about 10,000 years ago, with the beginnings of agriculture, population concentration grew exponentially, leading to the creation of villages and then towns and cities.
Agriculture also meant the domestication of animals for food and work, and many of our infectious diseases originated in animals; these are what we call zoonotic illnesses. The importance of this cross-connection between humans and animals has resulted in the One Health movement, which emphasizes that only by understanding the health of both humans and animals can we prevent diseases in our own species.
I was among the first supporters of One Health because it addresses such a critical reason for today’s increased risk of infectious diseases in humans.
Many infectious diseases, including poliovirus and variola major (smallpox), have adapted themselves solely to humans, with other variations (such as cowpox and monkeypox) affecting humans and other species. Zaire Ebola, the strain that caused the 2013–15 West African epidemic, is efficiently deadly to humans, with anywhere from one-third to one-half of the victims dying. Reston Ebola, the strain that played the lead in The Hot Zone, Richard Preston’s 1994 bestseller, was fatal to primates but left humans virtually untouched.
Each infectious disease needs a certain human or animal population to sustain itself. Measles, for instance, one of the more effectively transmitted infectious diseases there is, likely requires a contiguous population of several hundred thousand; otherwise, it dies out.
Some biological agents can simply lie in wait for the right time to strike. If we have chicken pox as children, the varicella-zoster virus that caused it can remain latent in the body for decades. Then, when we’re older and our immune system is weaker, it can break out in a form called herpes zoster, causing painful shingles. The bacterium Bacillus anthracis can lie dormant in spore form almost indefinitely, until it is inhaled or ingested or comes in contact with an open wound, at which point it will be reactivated and cause deadly anthrax in its unwitting host.
Once a disease effectively jumps from animal reservoir to human, it represents a new risk to its potential victim population, which has no biologic memory, and it takes time and trauma for that population (the surviving part of it) to form immunity. As civilizations grew and progressed, so did the speed and impact of infectious diseases. Yersinia pestis bacteria—the Black Death bubonic and pneumonic plague that wiped out between a quarter and a third of the European population in the fourteenth century—took only a decade to spread across Europe and continued to be deadly for more than a century.
But when the Europeans came to “settle” the New World two centuries later, they came upon peoples who were immunologically naïve to their bugs. The smallpox virus they brought with them cut the number of Timucuan Indians in Florida by half in six years—from roughly 722,000 in 1519 to 361,000 by 1524. Four years later, measles pandemic halved the population yet again. Similar courses had similar effects on other Native American civilizations, which the Spanish conquistadors took to mean that God favored their conquest and lust for gold.
As fast steamers replaced sailing ships and then trains superseded horse-drawn wagons, the efficiency of infectious disease spread picked up. That’s pretty much where we were at the beginning of the twentieth century.
Statistically, the worst pandemic of the modern era occurred in 1918, when the so-called Spanish flu swept the globe. In reality, it was not Spanish at all. It was just that Spain, neutral in World War I and thus a country that did not censor its press, reported it honestly and therefore was erroneously stuck with the rap. Conservative estimates have traditionally pegged the worldwide death toll at 40 to 50 million, but recent analyses suggest it might have been twice that, dwarfing the toll of the brutal and bloody world war that immediately preceded it.
For reasons we will discuss, the 1918 flu was an influenza strain like none other in recorded history. Could something like this happen again? You bet it could. In fact, you bet your life it could. But with all of the advances in medical science and communications in the past hundred years, would we be better prepared to deal with it?
Don’t be too sure.
The world is a far different place today than it was a century ago. In fact, the world is a far different place today than it was twenty-five years ago. And almost all of the changes that have taken place favor the microbe side of the war rather than the human side.
First, by its very nature, public health requires cooperation; communities and countries must come together. The worldwide smallpox eradication program worked because the two superpowers of the time—the United States and the Soviet Union—both agreed it was the right thing to do. Had either side not supported this effort, smallpox eradication would not have happened. And when those two gave marching orders, every other country in the world lined up behind them and saluted.
Since the fall of the Soviet Union, the world has changed. The nonprofit Fund for Peace’s Fragile States Index was much higher in 2016 than a similar study would have showed in 1975, and it is more difficult now than it was forty years ago to get the international community to work together to achieve a common goal. Today, there are more than forty countries with no more than a marginal ability to govern.
It’s not just Africa we’re talking about. In the Americas, as of this writing, Venezuela and Colombia are on the verge of economic and political collapse, based on falling oil prices. Brazil’s president has been impeached, its government is breaking down, and the state of Rio de Janeiro has declared a “public calamity.” Puerto Rico, part of the United States, is virtually bankrupt. All of these disruptions in governance can lead to major catastrophes in public health.
Internal and external terrorism is a constant threat, and suspicion is persistent. As of this writing, a number of polio vaccination workers have been murdered in several areas of Pakistan, where hard-line Islamists oppose the campaign as contrary to the will of God and a secret attempt to sterilize the population.
Second, population tends to expand exponentially, and more and more humans and animals are concentrated in close proximity. We’ve already noted the human population explosion: In 1900, there were an estimated 800 million people on the earth; by 1960 that number had risen to 3 billion. Today it is around 7.6 billion. The World Health Organization (WHO) estimates the world population will reach 10 billion by 2050. Most of that growth will be in the megacities of the developing world, where the unsanitary conditions, including the lack of safe water and sewers, make Dickens’s descriptions seem not so bad.
The concern we most often hear or read about animal populations around the world today is their serious loss in numbers, including the extinction of an increasing number of species. Yet there has also been an explosion in the population of food-production animals to feed the growing human population.
For example, in 1960, there were an estimated 3 billion chickens in the world; today there are approximately 20 billion. And since a chicken grows so quickly, the breast on your plate today may have been just an embryo as recently as thirty-five days ago. We can go through as many as eleven or twelve generations of chickens in one year.
Each one of these birds represents a potential test tube in which a new virus or bacteria can grow. And by the very nature of poultry production around the world, these birds are in close contact with humans; they share breathing space with those who care for them. The same is true for pigs. Today, there are more than 400 million pigs produced each year, and the pig happens to be the perfect genetic mixing bowl for the unstable and easily mutated avian and human influenza viruses.
To add fuel to the fire, it’s expected that chicken and pig populations will increase by at least 25 to 30 percent over the next twenty years to help feed the rapidly growing human population.
Third, changes in global travel and trade have made us truly a one-world economy. People, animals, and goods are moving around the planet in greater numbers than ever before and at unprecedented speed. Until the last century, most of the world, particularly the developing world, was rural and isolated. Most people never traveled more than a few miles from the villages in which they were born. In 1850, it took almost a year to circumnavigate the globe on a fast sailing vessel. Today, we can go round the world in less than forty hours by airplane. The first scheduled commercial air flight occurred in 1914, transporting passengers across Tampa Bay. A hundred years later, 8 million people take commercial flights each day; that’s more than 3.1 billion fliers annually.
The significance of the fact that any person can end up anywhere else on earth in a matter of hours is obvious. But just as significant is the idea that because of the global supply chain and the just-in-time-delivery practices affecting nearly all products and components, the impact of a pandemic will be far greater than one of similar virulence would have been in the past. As just one example, we may have among the world’s best medical infrastructures in the United States, but virtually all of our generic lifesaving pharmaceuticals are manufactured overseas. Let’s say there is a major epidemic in a region of India where many of our drugs come from. Lives will be lost in our own major cities because the critical medications just won’t be available.
For the year ending June 30, 2014, air carriers transported 186 million passengers between the United States and the rest of the world. The same carriers also transported 9.54 million tons of freight between these countries. Globally, more than 150 million tons of freight were transported by planes. Every day, up to 60,000 large cargo ships are traversing the oceans of the world, bringing cargo containers from one continent to another, and with them a number of infectious disease vectors such as virus-infected mosquitoes and contaminated agricultural products.
Ironically, the ways we have organized the modern world for efficiency, for economic development, and for enhanced lifestyle—the largely successful attempts to transform the planet into a global village—have made us more susceptible to the effects of infectious disease than we were in 1918. And the more sophisticated, complex, and technologically integrated the world becomes, the more vulnerable we will be to one disastrous element devastating the entire system.
The fourth factor in our war on microbes is global climate change. Frankly, we don’t know what the effects will be, but you can bet there will significant ones. Will malaria, which already kills between half a million and a million people each year, spread into areas farther from the equatorial region? This might happen with any of the tropical diseases, particularly those transmitted by mosquitoes, such as Zika. Will the midwestern winters no longer be cold enough to kill off the disease-causing agents of summer?
Malaria also highlights another important concept in public health: the distinction between epidemic and endemic diseases we alluded to earlier. Those more than half million fatalities in Africa far exceed any reasonable estimate of what Ebola could have caused in the 2014 outbreak. But malaria and other endemic diseases such as tuberculosis do not cause widespread panic in other countries or bring down governments. They don’t lead to threats to shut down airports and close borders.
In contrast to a chronic condition, an outbreak, particularly one caused by a virus transmitted simply by breathing the same air as those already afflicted or suffering a mosquito bite we don’t even feel or notice, creates a sense of panic combined with the struggle to understand the science and control the situation. This naturally leads to disproportionate disruption and impact. In the wake of the 9/11 attacks, a small amount of powdered anthrax sent through the US Postal Service to Capitol Hill and media figures, causing only twenty-two cases, still took billions of dollars to fix, closed down the Hart Senate Office Building across the street from the US Capitol for months, and paralyzed the mail delivery in the area. And anthrax is not a communicable disease the way Ebola and smallpox are. You don’t catch it from another infected person.
Therefore, as serious as epidemics and pandemics can be in medical terms, we have to understand that certain kinds of deadly outbreaks can bring panic and disorder far in excess of their simple numerical effect—the frequent disconnect between what has the greatest potential to kill us or hurt us and what frightens us or just makes us uncomfortable.
A pandemic can shut down regional, national, or even international commerce, which in turn can lead to economic chaos, which in turn can lead to destruction of confidence in unstable governments. If a government’s authority is shaky to begin with, the stress of a pandemic can lead to a failed state, which in turn can lead to anarchism and terrorism. At the same time, while the pandemic is occurring, other endemic and noninfectious diseases are still affecting the population, the combination of which can eventually tax or even break the existing healthcare delivery system.
In the three West African nations affected by the 2014 Ebola outbreak, crops were not harvested, schools shut down, borders closed, and the Peace Corps removed 340 volunteers. Because they were unable to receive medical care during the outbreak, almost as many people died from HIV, tuberculosis, and malaria infections as died from Ebola.
The very enemy we have devoted so much money and human resources to defeating since 9/11 can easily fill the leadership vacuum created by pandemic disease. In a very real sense, fighting infectious disease is, among other things, a matter of national security.