“The main fuel to speed the world’s progress is our stock of knowledge, and the brake is our lack of imagination.” — Julian Simon
“Man cannot survive except through his mind. He comes on earth unarmed. His brain is his only weapon.” — Ayn Rand
“All men by nature desire to know” — Aristotle
All of us have heard that 99% of the species that have ever existed on Earth are now extinct. Extinction events occur for myriad reasons, one of which could be an outbreak of an infectious disease. While there are countless portrayals of end of day scenarios in Hollywood movies and television programs, many of their post-apocalyptic worlds bear little resemblance to what could really occur with a large infectious disease outbreak amongst humans (as opposed to Christmas Island rats).
The most famous extinction event is, of course, that of the dinosaurs 66 million years ago. Though we tend to associate it exclusively with dinosaurs, the truth is that three quarters of animal and plant species perished during this period, formally known as the Cretaceous-Paleogene extinction event. The leading hypothesis, which has amassed enough supportive evidence to reach the level of a theory, points to an asteroid impact. Still, it is important to note that the impact alone, rather than cause mass extinctions, would have created changes in planetary conditions that made life impossible for those species unable to adapt to a markedly different habitat.
Such a cataclysmic result is not surprising, since many species had not developed resiliency mechanisms to cope with a major habitat change. Natural selection would not have produced superfluous traits (in the absence of an asteroid strike) on a large scale. The Cretaceous-Paleogene extinction event was a great culling, the survivors of whom had, by chance mutations, the characteristics that allowed them to survive.
An interesting footnote to this event is the idea (theory) that drastic reductions of sunlight killed those plants that relied on photosynthesis for life, resulting in the proliferation of non-photosynthetic organisms such as fungi. If, like me, you try to find an infectious cause in every event, you may wonder if the increase of fungi led to widespread fungal infections, magnifying the devastation posed by the loss of nutritious vegetation relied upon by most species. Today, fungal infections annihilate species of reptiles and amphibians.
Whatever the mechanics, the Cretaceous-Paleogene extinction event is the most widely known of its kind. For many species – unequipped by evolution for changes in habitat, predator-prey relationship variations, and myriad other factors – micro-extinction events occur continuously.
As I have tried to sketch out throughout the book, there is a lot of reasons to be wary of infectious disease outbreaks but many reasons to believe that nothing fathomable could spell the end of our species—not Ebola, not bird flu, not HIV, and not COVID-19. While there is much we do not know about the microbial world and countless possibilities, one thing stays true: human beings are a resilient species, the most resilient.
In recent years the emergency preparedness community, of which I am a part, has made resiliency a buzzword that has crossed into the vernacular of the public. Resiliency refers to the ability to recover from some sort of shock whether it is a hurricane, a pandemic, or even the loss of your job. Resiliency, on a larger scale such as that of a city, speaks to the ability to get back to normal life after some major alteration in daily life and the same can be said of a species. Humans showed resiliency to the Black Death, to the HIV pandemic, and The Great Influenza; we are showing resiliency to COVID-19.
But what enables resiliency? Is resiliency just duct tape, batteries, and flashlights. Why is it that humans are the species that can cultivate resiliency as opposed to relying on instinct and genetic programming like other organisms do?
Humans have the ultimate resource: their conceptual consciousness, which is capable of abstract thought, long-range planning, and principled action. All those aspects make possible the foresight to buy duct tape and batteries. It is the human mind that makes possible all our technological marvels that allow real resiliency to inhere in the species. Vaccines, antibiotics, and even hospitals are components of the human species resiliency mechanism. In a manner of speaking, all this technology obviates the need of a biblical arc to protect us from doom and in another sense, we already exist in an arc-like environment.
The other aspect of resiliency that is common to all organisms is our genetic makeup. Evolution is not a process that occurs arbitrarily, natural selection directs it. Natural selection is an exacting process that magnifies, over time, even the miniscule advantage one trait possessor has over another. Humans emerged from the battles of natural selection and possess certain attributes, such as the powerfully adaptive immune system, that suits them well for life on this planet. As Darwin’s grandfather Erasmus eloquently said, “All nature exists in a state of perpetual improvement.”
Though, as I emphasized, we live on a planet—and have a body populated by— microbes, our evolution occurred in this context, and we have the means to flourish in such an environment. We not only flourish but we have evolved to enjoy a symbiotic relationship with bacteria in our bodies and in our environment. While I often emphasize the pre-industrial world human life as short and fraught with disease, humans survived in those times and their population grew even before Jenner’s development of vaccines and the antibiotic revolution.
Part of our evolutionary heritage is our immune system, one of the most complex on the planet, even without the benefit of vaccines or the helping hand of antimicrobial drugs. This system, when viewed at a species level, has the ability to respond to almost any enemy imaginable with its adaptability. The immune system’s response capacity coupled to genetic variations amongst humans (such as genetic resistance to HIV and malaria) almost ensures that any infectious disease onslaught will leave a substantial proportion of the population alive to rebuild, in contrast to the fictional Hollywood versions.
Natural selection favors traits that confer survival advantage. Humans, their immune systems, and their unique conceptual and volitional consciousness emerged out of an environment with myriad potentially lethal infectious disease-inducing microbes. While the immune system’s role can never be understated, an even more powerful protector is the faculty of consciousness. Humans are not the most prolific, quickly evolving, or strongest organisms on the planet, but as Aristotle identified, humans are the rational animals—and it is this fundamental distinguishing characteristic that allows humans to form abstractions, think in principles, and plan long-range. These capacities, in turn, allow humans to modify, alter, and improve themselves and their environments. Consciousness equips us, at an individual and a species level, to make nature safe for the species through such technological marvels as antibiotics, antivirals, vaccines, and sanitation. When humans began to focus their minds on the problems posed by infectious disease, human life ceased being nasty, brutish, and short. In many ways, human consciousness became infectious diseases’ worthiest adversary.
On my first trip to the Galapagos Islands, the area of the world that provided much of the data that Darwin induced the idea of evolution from, I spent hours in conversations with naturalist guides. In one such conversation, centering on Zika virus, he endorsed the view – with which I disagree –that humans should not seek to modify their lives in a way that interferes with natural selection. Not only do I disagree with this statement morally – I take human life as my standard of value – but the statement ignores the fact that our consciousness — a biological faculty that evolved with us — is a faculty that has the capacity to use nature to create city sanitation systems, vaccines, antibiotics, microscopes, and genetically modified mosquitoes. It is striking to need to emphasize that humans possess this remarkable form of consciousness as the very result of the natural selection the guide was saying humans should not interfere with. Exercising our consciousness is what has allowed humans to rise to the heights we have on this planet. So, allowing natural selection to work is just what is happening when we make vaccines, antivirals, and the like to promote our species’ well-being. So, when I, as an infectious disease physician, intervene on an illness I am not preventing natural selection from occurring I am exemplifying it.
While I have tried to defuse the fears surrounding certain diseases and direct attention to other threats, it is important to remember all the hypothetical caveats that are in place. While it is extremely intellectually stimulating to contemplate space microbes, dark matter attacks, and the like our chief infectious disease threats throughout time have come from the “known” categories. Even surprise infections like SARS and COVID come from a known viral family whose ability to cause a pandemic the former dean at an institution I am affiliated with presciently predicted decades earlier. There has not been a true unknown unknown outbreak and most of our dark matter infections and mysterious illnesses reflect our technological diagnostic limitations which the advent of a whole host of modern technologies are now increasingly illuminating. What was once mysterious will become routine, especially with the revolutionary advances in synthetic biology, nanotechnology, and systems biology.
The above is not meant to allay all fears for to totally adopt a Panglossian viewpoint would be foolish—and dangerous. We do face countless infectious disease threats and if not handled appropriately severe calamity could, and will, ensue. From the rise of antibiotic-resistant bacteria to the explosive nature of widespread foodborne outbreaks to the looming threat of pandemic influenza to the return of the primitive exemplified by the anti-vaccine and anti-pasteurization movements, humanity has more than its hands full in this realm.
The Ebola outbreak in West Africa concretized for many in industrialized nations just what could happen if an outbreak burned out of control and teetered a society towards failure, but it need not be that way in Africa or anywhere on the planet.
Just 6 years later, a novel coronavirus swept the world in a fashion not seen since 1918. Disruption, death, and divisiveness were what it wrought. However, pathbreaking vaccines were in arms in less than a year accompanied by monoclonal antibodies, home diagnostics, antivirals, and an explosion of knowledge about the novel virus’ epidemiology, clinical course, and treatment.
***
We stand today on the shoulders of giants who have developed so many of the tools that enable the human species to flourish each year better than the last. We also live today amongst scientists and physicians developing the next generation of these tools that will stretch our ability even further. This never-ending quest to understand reality, which stretches all the way back to Thales, is the ultimate safeguard to any existential threat we might face. Paraphrasing a great philosopher, to save the world [from infectious disease] is simple, all one has to do is think.