From Killer To Common Cold

Herd Protection and the Transitional Phase of Covid-19

David M Graham

• Editorial: FiPhysician
• Año: 2020
• ISBN:
  9780578772868
• Edición: 1
• Categoría: Medicine
• Categoría: Infectious Diseases

We cannot eradicate Covid-19, but humans can help the virus grow to be more benign.

To get there, we must enter the Transitional Phase, when Covid-19 transforms from pandemic to another common cold coronavirus. Understanding what a virus wants and how a virus views the world helps. With knowledge of existing human coronaviruses and basic viral/host interactions, we come to understand that herd protection-not herd immunity-is the goal. Immunity is not permanent from coronaviruses, and a vaccine will not be a silver bullet for the vampire that lives within our cells.

After the epidemics are over, new cases do not go away. With or without a vaccine, we must learn how to live with Covid-19 in the world. What will the next few years look like? How can you protect yourself? And how can we help Covid-19 reach its destiny-to become the common cold?

 

 

 

 

 

 

1 How a virus views the world

 

 

A virus, yet again, changed the world. A bag of protein and genetic material intent on making copies of itself has been unleashed on humans.

SARS-CoV-2—the virus responsible for causing Covid-19—isn’t even a living thing. A virus is just a tiny collection of proteins and genetic material wrapped in your own cellular membrane with one goal: to make more copies of itself.

This killer virus jumped from bats into humans, rapidly traversing the globe in the respiratory secretions of an interconnected planet. Yet, since the introduction of animal domestication, human pandemics from viruses have been relatively commonplace. These human pandemics have shaped our shared histories.

Consider a virus like smallpox. Once a common cause of childhood death and disfigurement, evidence of this virus has been found on mummified remains from ancient pharaohs. Waves of this viral pandemic wiped out vast numbers of humans, from European royalty to entire Aztec and Inca civilizations. Smallpox influenced politics in Europe and decimated the native populations of the New World, allowing settler colonialism to flourish. There are multiple examples of pandemics every century, and now, after a one-hundred-year hiatus, another pandemic virus is upon us.

 

Although viruses are not living, it might be helpful to consider viruses like SARS-CoV-2 as if they lived, breathed, and walked, just like us. What if we were to walk a mile in the shoes of SARS-CoV-2? How does a virus see its human host? What inherent restrictions do viruses have, and how do human cultures shape those restrictions? Can we learn something about Covid-19 by thinking about how a virus experiences the world?

The interaction between humans and viruses is complicated. Anthropomorphizing viruses allows us to think beyond the week- or month-long pandemic planning horizons that governments use. On one side, there is a virus that evolves and modifies the rules of the game while in progress. On the other side, we humans strive to understand the rules, anticipating what changes (both for us and the virus) are inevitably in store. One thing is clear—this virus, SARS-Co-V-2, will change people around the globe.

Human culture is built upon identifying problems and organizing people to create solutions. Where we live in the world drastically affects how we experience Covid-19. We all have different social norms, political gambits, and ever-changing attitudes towards the virus. Culture affects the way we see Covid-19.

Moreover, many have struggled to learn the science of virology and epidemiology through the lenses of political, social, and economic concerns. We are seeing the messy give-and-take of the scientific process in action, occurring simultaneously with haphazard policy proposals. Too often during this pandemic, policymakers endorse a solution now, only to scorn the same solution later. The political response to the pandemic feels like constructing your parachute after jumping off the plane.

Individuals, on the other hand, deal with viruses differently, both physiologically and through their personal decisions. We all have slight variations in our immune systems and underlying health, which massively differentiates our experience of Covid-19, both for ourselves and our family members. Our personal experience with the virus shapes both the way we view what individuals can do now and what we should expect in the future.

Instead of focusing on the rapidly changing political and scientific landscape for bites and bytes of information, what if we instead profiled Covid-19 like we were profiling a criminal? Let’s line up all the usual suspects! Who (or what) has done something like this before? What can we learn by looking at prior pandemics, and, more specifically, at the family of coronaviruses that already infects humans? We might not be able to sentence our culprit (or cure it for that matter), but we can hopefully learn enough about Covid-19 to predict parts of its behavior and know what to expect in the next few years and beyond.

Profiling depends on homology and behavioral consistency. Homology, the idea that similar crimes are committed by similar offenders, allows us to look at other pandemics and consider how Covid-19 is different. Can we learn something from the crimes of smallpox and influenza that might inform us about the future of Covid-19? Behavioral consistency speaks to the idea that an offender’s crimes will be similar in nature. We know there are seven other human coronaviruses currently in existence. Can we look at the crimes of the other coronaviruses and figure out what to expect with Covid-19?

Rather than using the give and take of scientific progress to predict the future of Covid-19, what if we used what we already know about evolution and virus/host interactions to make future inferences? As we build the scientific evidence base to better understand Covid-19, is there a way to know now, in advance, how it will all end? Yes.

 

I believe the destiny of SARS-CoV-2 is already written. With or without a vaccine, with or without an effective treatment, with or without expected technological advances, we are destined to interact with this virus forever. Only a major paradigm-shifting development of the future—something truly out of left field—will rid this world of Covid-19.

 

This book is not so much a tale of science on the ground today. The science is changing too rapidly to consider writing a book on that topic. Instead, this is a tale of evolutionary biology and the natural limitations placed on viruses, humans, and the co-evolving cultures each group simultaneously creates. Within those limitations, we know that SARS-CoV-2 is not eradicable and will become endemic.

There are already four coronaviruses that are endemic and cause the common cold. Endemic means that they circulate widely, at all times, and in low levels in human populations throughout the world. SARS-CoV-2 will become the fifth endemic human coronavirus. Believe it or not, the process of a coronavirus becoming endemic has already happened at least once before in our written history.

Even though we cannot eradicate Covid-19, it will be less lethal in the future. This is predictable either through evolution of the virus itself or through changes in its host. Humans, our immune systems, or our cultures will change the face of this killer disease so that it resembles the common cold.

 

Pandemics and infectious diseases have killed more people and shaped human history more than any other aspect of nature. We have been in an arms race with infections since the beginning. Until the twentieth century, infections killed more soldiers at war than human enemies did. We are, and have been, in a constant struggle against infections for millennia, though we forget this when only looking back over our own lifetime. Hygiene, clean water, antibiotics, vaccines, and good old public health have changed the nature of infectious diseases in modern society.

Although there are still many places on earth where infectious diseases are the number one killer of young children, diseases of civilization such as heart disease and cancer have overtaken infectious causes of death in wealthy countries. The impact of infection on our daily life has faded. It has been over one hundred years since the last truly devastating pandemic plagued us. We forgot. We did not plan, and deaths and disabilities from Covid-19 are the inevitable and unfortunate consequences of not preparing for the usual suspects to return to their old, criminal ways.

 

This will be a short book. Using basic virology and evolutionary biology, I aim to convince you that Covid-19 will become endemic no matter what humans do. We will need to learn to live with this virus, and I hope to show you how to do so.

We’ll start by reviewing some basic science about viruses and how they interact with hosts. Next, we will look at influenza and discuss some prior pandemics, contrasting influenza to the family of coronaviruses that already live in and among us. Once we have a basic understanding of viruses (the usual suspects), we will learn a little about epidemiology, viral replication dynamics, and herd immunity. From this, I will demonstrate how eradication of SARS-CoV-2 is unlikely and discuss how the next few years may play out. Covid-19 infections will continue during what I call the “Transitional Phase,” as we progress from epidemic to endemic. Finally, we will review how a current common cold coronavirus, OC43, went from epidemic to endemic during our written history.

Covid-19 is here to stay, but rather than drinking from the fire hose of ongoing scientific discovery, what can we learn from a review of science theory? We have evidence and probable cause. It is time to prosecute SARS-CoV-2 and understand the fallout from the crime. Instead of looking at statistics, modeling, and the ongoing messiness in medical journals, let’s look at history to see potential futures.

 

2 What Does a Virus Want?

Viruses are explosive.

They are an aggregation of proteins and genetic material with a single goal—to make more of themselves. Some viruses literally blow the cell they are trapped inside up in order to escape. When given enough resources, they demonstrate exponential, explosive growth. Remember that viruses, unlike bacteria, protozoa, and fungi, aren’t even alive. They are the ultimate parasites that require a living organism—often you—to survive and reproduce.

SARS-CoV-2 is the virus that causes the disease Covid-19. The “CoV” stands for coronavirus, which is a large family of closely related viruses that cause various illnesses in many different species. We will learn about the human coronaviruses in chapter 4, but first, we’ll discuss what exactly a virus is and how it interacts with its host.

Viruses are small—much smaller than even bacteria. They are the ultimate minimalists, carrying only what they need to get from one host to another. They must do three basic things. First, they must transfer from host to host via the environment. Then, once in a host, they need to spread from cell to cell. In the cell, they make copies of themselves.

Viruses take over the metabolic machinery of a cell and then make so many copies of themselves that they obliterate the cell. Next, they find another cell to infect. Within a host, only the host’s immune system can break this chain of cell-to-cell transfer.

Surviving in the environment outside the host, however, is difficult. The virus must leave a host (usually via sneezing, coughing, or diarrhea) and get onto, and then into, another host. The environment is a hostile place for viruses. They are diluted by space and time and desiccated by sunlight. If they land on the wrong type of host, it is all for naught. A virus only infects one species of animal.

To protect themselves from the environment, enveloped viruses use a lipid membrane to coat themselves. Not infrequently, viruses actually use your own cell’s lipid membrane to do so. Smart! They use your cellular machinery to replicate, and your cell’s membrane as a coat. They are minimalists, but not ideal houseguests.

Image adapted from “Why Soap Works” by Jonathan Corum and Ferris Jabr, New York Times, 3/13/20.

Next, there are little protein spikes that stick out of the virus and latch on to your cells. The proteins that stick out of coronaviruses look like the solar corona on electron micrographs, hence the name. The protein spikes attach like a lock and key to receptors of your cells. These receptors are there for some other functional purpose, but the virus learns to take advantage of them in order to gain entry. A virus attaches protein spikes to your cell’s receptors, allowing it to enter your cell. Once inside, the virus hijacks your cellular machinery and uses it to make copies of itself.

Viruses have either RNA or DNA as their genetic material. RNA viruses mutate more rapidly and can possess some extra proteins to replicate. We can sometimes target those extra proteins with medications, which make RNA viruses slightly more treatable.

Coronaviruses are large, enveloped RNA viruses. They are found in many different animal species and cause different syndromes in different animals. Cows and pigs get diarrhea from their versions of coronavirus, whereas other species can have respiratory, neurological, and asymptomatic illnesses.

Humans are exposed to animal coronaviruses all the time. However, as the virus is adapted to living in its host species, a great majority of the time it c...