Pandemics: History and Prevention – Part 1

I’m Dr. Michael Greger and this is Nutrition Facts. 

There’s one thing we’ve been thinking about a lot lately, and that’s how to stay healthy in the middle of a global pandemic. Especially since we’ve learned that those with underlying health problems like obesity, hypertension, diabetes, and heart disease are more likely to have serious complications if they contract COVID-19. So what do we do? We try to stay healthy with evidence-based nutrition.

Today on the show,  we go back in time –more than a decade to revisit a very timely subject:  how to prevent the emergence of pandemic viruses in the first place.  I recorded this when I was public health director at the HSUS –in Washington, DC.

The two greatest threats facing humanity, according to the United Nations are climate change and emerging infectious disease––particularly pandemic influenza. The current focus of pandemic discussions and debate understandably centers on what we in the public health community refer to as secondary prevention: mediating the impact of the next pandemic, an intervention analogous to mammography. Mammograms don’t prevent cancer, but if caught early enough, for example, we may be able to decrease morbidity and mortality. And, the same with pandemic planning. But what of primary prevention, the possibility of preventing the emergence of pandemic viruses in the first place? Like cancer, the root cause is likely multifactorial, difficult to tease out, but a question worth exploring, nonetheless, and the question I’d like to address here today.

Let’s go back a few years. 1981. Here in the United States, Ronald Reagan takes the oath. MTV starts broadcasting Indiana Jones, and Pacman mania is all the rage. In June, the CDC released a tiny bulletin. Five men in Los Angeles, it seems, were dying with a strange cluster of symptoms. From humble beginnings, AIDS has since killed 25 million people. Now, the spread certainly of the AIDS virus has been facilitated by promiscuity, blood banking, IV drug use; but where did this virus come from in the first place? And, of course, AIDS is not our only new disease. There’s SARS, Ebola, mad cow, bird flu… But from where do emerging diseases emerge? Well, let’s go back a bit further, much further. Human beings have been on this earth for millions of years, yet throughout most of human evolution, there were no epidemic diseases.

No one ever got the measles, because measles didn’t exist. No one got smallpox, no one got the flu, not even the common cold until 10,000 years ago. Medical anthropologists have identified three major periods of disease since the beginning of human evolution, and the first started just 10,000 years ago, with the domestication of animals. When we brought animals into the barnyard, they brought their diseases with them. When we domesticated cows and sheep, for example, we also domesticated their Rinderpest virus, which turned into human measles, now thought of as a relatively benign disease. Over the last 150 years, measles has killed 200 million people. And, in a sense, all those deaths can ultimately be traced back just a few hundred generations to the taming of the first cattle. Smallpox likely came from camel pox. We domesticated pigs, and got whooping cough. We domesticated chickens, and we got typhoid fever and Typhoid Mary, and domesticated ducks, and got influenza. Before the domestication of ducks, likely no one ever got the flu. Leprosy likely came from water buffalo, and the common cold from horses. How often did wild horses have the opportunity to sneeze into humanity’s collective face until they were broken and bridled? Until then, the common cold was presumably only common to them.

In his Pulitzer Prize-winning book, Guns, Germs and Steel, Professor Diamond tried to explain why the diseases of the landing Europeans wiped out up to 95% of the native Americans, and not the other way around. Why didn’t native American plagues kill the Europeans? Well, because there were no plagues. In his chapter, “Lethal Gift of Livestock,” he explains how before the Europeans arrived, we had buffalo, but no domesticated buffalo; so, no measles. American camels were wiped out in the Pleistocene ice age; so, no smallpox. No pigs, and so no pertussis. No chicken, so no typhoid. So, while people were dying by the millions of killer scourges in Europe and Asia, none were dying with diseases in the so-called new world because there weren’t essentially foreign animals to domesticate. There wasn’t this spillover of animal disease.

The next great period of human disease started just a few hundred years ago with the Industrial Revolution of the 18th and 19th centuries, leading to an epidemic of  the so-called diseases of civilization: diabetes, obesity, heart disease, cancer, etc. But by the mid-20th century, the age of infectious disease at least was thought to be over. We had penicillin, we conquered polio, eradicated smallpox. In fact, in 1968, the US Surgeon General declared the war against infectious disease has been won. In 1975, the Dean of Yale School of Medicine pronounced that there were no new diseases to be discovered—except maybe lung cancer. But even Nobel laureates were seduced in the heady optimism of the time. One famous virologist wrote, in a 1962 textbook, “To write about infectious disease is almost to write about something that’s passed into history. The most likely forecast of the future of infectious disease,” he wrote, “is that it will be very dull.”

But then, something changed. After decades of declining infectious disease mortality in the United States, the trend has reversed in recent decades. But then around 1975, it started to go back up. The number of Americans dying from infectious disease started to go back up. Starting around 1975, new diseases started to emerge and re-emerge at a rate unheard of in the annals of medicine. More than 30 new diseases in 30 years––mostly newly discovered viruses. In fact, the whole concept of emerging infectious disease has gone from a mere curiosity in the field of medicine. Now it’s an entire discipline, really moved to center stage.

We may soon be facing, according to the US Institute of Medicine, what they call a catastrophic storm of microbial threats. We are now smack dab in the third era of human disease, which seems to only have started about 30 years ago. Medical historians have called this time in which we live the Age of Emerging Plagues, almost all of which come from animals.

But we domesticated animals 10,000 years ago. What has changed in recent decades to bring us to this current situation? Well, we are changing the way animals live. Take Connecticut, for example, where in 1975, Lyme disease was first recognized. Since, spread across all 50 states affecting an estimated 100,000 Americans since its emergence. Lyme disease is caused by bacteria-infested deer ticks, but the primary host is actually not deer, but the white-footed mouse. The ticks themselves, not quite as cute really, but we’ve been sharing the woods with these fellows forever. What changed recently was suburbia. The black-legged ticks live on the white-footed mouse, kept at bay by woodland predators. But then, developers came in and chopped up America’s woodlands into subdivisions, scaring away the foxes and bobcats, and now we have more mice, more ticks, and more disease.

We are changing the way animals live. Going back a little farther, with the big cattle-producing nations fighting during the Second World War. What Argentina did, took advantage of the situation by dramatically expanding its beef industry at the expense of its rainforest. There we discovered the deadly human virus, or rather it discovered us, and the so-called hamburger-ization of the rainforest exposed hemorrhagic fever viruses all across the continent subsequently. Turning to the other side of the world, cutting into Africa’s rainforests exposed a number of other hemorrhagic fever viruses, including Lassa virus, Rift Valley fever, and, of course, Ebola. Now the inroads into Africa’s rainforest were logging roads cut by transnational timber corporations hacking deep into the rainforest, dragging along a hungry migrant workforce, which survived on bush meat: wild animals killed for food. Now this includes upwards of 26 different species of primates, including a number of endangered great ape species, gorillas, chimpanzees, who are shot, butchered, smoked, and sold as food. Now by cannibalizing our fellow primates, we may be exposing ourselves to viruses particularly fine-tuned to our own primate physiology. In fact, recent outbreaks of Ebola, for example, have been traced to the exposure to the bodies of infected great apes hunted for food. Now Ebola is one of our deadliest infections, but not efficiently spread, compared to a virus like HIV.

The leading theory as to the emergence of the AIDS virus is direct exposure to animal blood and secretions as a result of hunting, butchering, and the consumption of contaminated bush meat. Experts believe the most likely scenario is that HIV arose from humans sawing their way into the jungle, butchering chimpanzees for their flesh along the way. Now in many countries in Africa, the prevalence of HIV exceeds 25% of the adult population, leaving millions of orphan children in its wake. Someone butchered a chimp a few decades ago, and now 25 million people are dead. But wildlife has been hunted for thousands of years. Yes, but never before like this.

With the demand for wildlife meat outstripping local supplies, what countries have done is set up these intensive captive production farms, cramming wild animals in these cramped filthy cages, and then smuggling them around the world. This intensive commercial bush meat trade actually started in the live markets of Asia, particularly the Guangdong province, a southern province surrounding Hong Kong, from which the current bird flu threat arose. The civet cat, a popular commodity in these Chinese animal markets. In addition to being raised for their flesh, they also produce the most expensive coffee in the world. So-called fox dung coffee is produced by feeding coffee beans to captive civets, and then—you guessed it— recovering the partially digested beans from their feces. A musk-like substance of buttery consistency secreted by the anal glands is said to give this coffee its distinctive favor. One might say this unique drink is good to the last dropping. I’m sorry. This animal was blamed for the SARS epidemic. Quoting from the medical Journal, Lancet, “A Culinary Choice In South China.” “A culinary choice in South China led to a fatal infection in Hong Kong.”

Subsequently, 8,000 cases of SARS. Nearly a thousand deaths, 30 countries, six continents. Maybe they should have just stuck to Starbucks. These live animal markets took a class of viruses, which in human medicine we had only known for causing the common cold, and seemed to turn them into a killer, SARS, which then spread around the world. Viruses can escape rainforests in animals, live or dead, as pets or as meat. In 2003, the exotic pet trade brought monkey pox from the jungles of West Africa to Wisconsin. Bird-smuggling may have actually been what brought West Nile virus to the Western Hemisphere. Here, it hits New York in ’99, and since spread across the country. Hundreds of human deaths, thousands of cases, all perhaps because of a single imported pet bird.

So, we are changing the way animals live, contributing to the emergence of these new diseases. But, you know, there’s one way we have changed our relationship with animals that really out shadows all the rest. In response to this torrent of emerging and re-emerging infectious diseases, the world’s three leading authorities got together for a joint consultation. The World Health Organization, the Food and Agriculture Organization of the United Nations, and the World Organization for Animal Health (the world’s leading veterinary authority), got together to uncover the key underlying causes of this age of emerging plagues. They came up with four, four main risks––four main themes of risk factors for the emergence and spread of these new diseases. Yes, they talked about the exotic pet trade. They talked about bush meat, but number one on their list was this increasing demand for animal protein the world over. Yes, we domesticated animals 10,000 years ago, but never before like this––especially pigs and poultry.

Chickens used to peck around the barnyard, but now chickens raised for meat are typically warehoused in sheds containing tens of thousands of birds. About half of the egg-laying hens on this planet are now confined in what are called battery cages. These small barren wire enclosures extending down long rows and windowless sheds; can be up to a million birds on a single farm. About half of the pigs on the planet are now again crowded into these intensive confinement operations. You know, old MacDonald’s farm has since been replaced by the new MacDonald’s farm. These intensive systems represent the most profound alteration of the human-animal relationship in 10,000 years. And, no surprise, they are breeding grounds for disease.

A few snapshots. China, 2005, the largest pork-producing nation suffers an unprecedented outbreak of an emerging pig pathogen, strep suis, causing meningitis and deafness in people handling infected pork products. Hundreds of people infected, the deadliest strain on record. Why? Well, according to the World Health Organization, indeed it seems to be these intensive confinement conditions. The USDA elaborates, “All strep suis starts out harmless as natural gut flora, but then the immunosuppressive effect of stress, due to overcrowding, inadequate ventilation, causes the bug to go invasive, causing infections of the brain, blood, lungs, heart, and death.” Starts out harmless, turns deadly. That’s what these kind of conditions seem to be able to do. This is not, arguably, how animals were meant to live.

Pig factories in Malaysia birthed the Nipah virus, one the deadliest of human infections: a contagious respiratory ailment killing 40% of those it infects, causing relapse and brain infections, propelling it onto the official U.S. list of bioterrorism agents. And again, according to one of the leaders of the field, it seems to be the way in which we now raise these animals. So, the three eras of human disease can be characterized perhaps as first, the diseases of domestication, then the diseases of industrialization, and of, finally, of land-use and agricultural intensification. We took natural herbivores like cows and sheep, turned them into carnivores and cannibals by feeding them slaughterhouse waste, blood, and manure, and then we took downed animals, too sick to even walk, fed them to people, and now we have mad cow disease. We feed antibiotics to farm animals by the truckload.

This is the total amount of antimicrobials used for all of human medicine every year. Now, contrast that with the amount we feed to farm animals, just to promote growth, or prevent disease, in such a stressful unhygienic environment. Millions of pounds a year, and now we have these multi-drug-resistant bacteria, and we as physicians are running out of good antibiotic options. Scientists at NYU traced the path of some of these “super bugs” starting, for example, with the mass feeding of the Cipro class of antibiotics to chickens, and then we––there is a fecal contamination of the carcass at slaughter. We buy chicken at the supermarket, polluted with fecal material, leading to longer and more severe human infections.

The CDC recently really cinched it. They spent a million dollars over a three-year period doing rectal swabs of newly admitted hospital patients. This is what they found. Essentially, they found zero growth of these antibiotic-resistant bacteria within the bodies of those that had zero contact with fresh or frozen poultry. But at least these so-called super bugs aren’t effectively transmitted from one person to the other. With the seeming propensity of industrial animal agriculture to churn out these novel lethal human pathogens, what if these animal factories gave rise to a virus capable of a global pandemic of disease?

Let me put these new animal disease threats in perspective. SARS infected thousands of human beings, killed hundreds; Nipha infected hundreds, killed scores. Strep suis infected scores, killed dozens. Now AIDS has infected millions, but there’s only one virus on the planet that can rapidly infect billions, and that’s influenza. Influenza, the so-called last great plague of humankind, is the only known pathogen capable of truly global catastrophe these days. Unlike many other important diseases like malaria, which are largely confined at the equator, or a virus like HIV, which is only fluid-borne, the influenza virus is considered the only pathogen capable of literally infecting half of humanity within a matter of months.

Now in the 4,500 years that we as species have had influenza, since the first domestication of birds, influenza has always been one of our most contagious known diseases. But only since the emergence of this highly pathogenic, highly disease-causing strain, H5N1, has the influenza virus also emerged as one of our deadliest. H5N1, spreading out of Asia, 2004, 2005, 2006, and continuing to this day, has only killed about a hundred, a few hundred people. And not to minimize, each death is a terrible tragedy. But in a world in which millions of people continue to die of diseases like AIDS, tuberculosis, why is there so much concern about the so-called bird flu? Because it’s happened before. Because the last time a bird flu virus adapted to human beings, it triggered the worst plague in human history: the influenza pandemic of 1918.

Modern flu strains tend to spare young healthy adults, but the 1918 virus killed people in the prime of life. In 1918, a quarter of all Americans fell ill.

Humanity’s greatest mass murder alluded scientists for nearly a century before a mass grave in Alaska was unearthed.  Victims of the pandemic frozen in the permafrost for 80 years.  Traces of virus allowed scientists to piece together letter by letter the genetic code of the 1918 virus solving perhaps the greatest medical detective story of all time. 

Humanity’s greatest killer was bird flu. First civilian casualty in the U.S. was September 11th, ironically, 1918. And this is 1918 now. We’re talking steam locomotive here. Scientists at the Imperial College of London ran a simulation to see how a pandemic might spread today in the UK. In 1918, between 50 and 100 million people lost their lives. A similar virus today could kill many, many more. What started out for millions as muscle aches and a fever ended days, or even hours, later, with many people bleeding from their eyes, from their nostrils, from their ears, into their lungs. Homeless orphans, their parents dead, wandered the empty streets. One agonized official in the stricken East sent an urgent warning West. “Hunt up your woodworkers and set them making coffins, then take your street laborers and set them to digging graves.”

Many victims strangled in their own bloody fluids. Their corpses, tinged blue from suffocation, were said to have been stacked like cord wood outside of morgues, and cities ran out of coffins, so they dug mass graves. That bird flu-originating virus killed more people in 25 weeks than AIDS has killed in 25 years. No war, no plague, no famine has ever killed so many people, in so short a time, as the 1918 pandemic.

Yet in 1918, the mortality rate of this disease was less than 5%. Currently, H5N1 is officially killing over half of its human victims. Don’t even seem to get a coin toss as to whether or not one lives through this disease. Dr. Robert Webster, the world’s leading authority on bird flu: “If we go back to 1918, 2.5% of people died. How many people are dying with bird flu? 50%. We’ve never seen such an event since the time of the plagues.”

Up to 60 million Americans come down with the flu every year. What if it suddenly turned deadly? That’s what keeps everyone up at night: the possibility, however slight, that a virus like H5N1 could trigger a human pandemic. That’d be like combining one of the most contagious known diseases, influenza, with one of the deadliest, like crossing a disease like Ebola with the common cold.

Be sure to listen in next week for part two of my talk on the History and Prevention of Pandemics.

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Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.