THREATS, OUTBREAKS, EPIDEMICS, AND PANDEMICS: A PRIMER
UNTIL A few years ago, many scientists had banished words like “threat” and “danger” from our vocabulary. In an attempt to be more rigorously quantitative and less emotional, we began to write about risks. Our response to danger was called “risk management.” A risk is a threat or a danger that you put into a box. Then you can count boxes, and manage them. The assumption in risk management is that you can quantify danger. This is only partially true.
Epidemiologists sometimes define an epidemic as more cases than they would expect, or as “unusually high rates.” But measuring this isn’t as simple as it sounds. We can ask, first of all, whether in our case numbers we are counting people exposed to a virus (and who may be test-positive), people who have been infected but don’t show any clinical disease, people who are clinically ill, or people who die. We might, if we are the World Bank and are worried about economic impacts, try to calculate disability-adjusted life years; that is, how many years of economically productive life are lost. This means that the younger you are when you get sick, the greater the impact (assuming you are economically productive).
Once we decide who and what to count, we are faced with another set of questions. What are we referring to when we say “expected” or “usual”? That is relatively easy, at least from a scientific point of view. The expected or usual numbers are those we’ve seen over the past few decades. Even if the numbers of cases are unexpected or unusual, however, we need to ask: Are we dealing with a disease that is important?
How do we assess importance? Is it a scientific decision? Are authorities more hesitant to use the loaded word “pandemic” for some diseases, preferring to speak of a “global epidemic” of AIDS or “high rates” of malaria or diarrhea in certain parts of the world? If so, why is that? Do some diseases so radically and explicitly expose global economic inequities that the wealthy owners of global institutions would prefer to focus on those that more directly threaten Europe and North America and for which a technical, money-making fix is more likely to be found? Hey, I’m a curious epidemiologist. I’m just asking. The truth is that although words like “outbreak,” “epidemic,” and “pandemic” have a scientific ring to them, and some grounding in science, their use is very political.
Now, after decades of quantitative risk management, in the new age of emerging infectious diseases such as bird flu, SARS, Ebola virus disease, and COVID-19, we seem to be back in a jungle of threats and dangers. If SARS-COV-2 has taught us anything at all, it’s that even our best quantitative, scientific measurements cannot give us all the answers we want.
Before we dive into what we mean by a pandemic—that equivalent to the man-eating lion in the dark forest—let me begin the definition with something smaller, at least in terms of numbers: an outbreak. An outbreak occurs when a relatively small group of people or animals or plants gets sick, as when everyone gets sick after eating a warm potato salad on a sunny day. The source of an outbreak can usually be traced to one particular event or exposure.
The next step up from an outbreak is an epidemic, which is like an outbreak, only huger. The word “epidemic” goes at least as far back as Homer, in about the eighth century BC. Homer used it to refer to someone in his or her own country, as differentiated from a traveler. It had connotations of “indigenous” or “endemic.” Hippocrates, in 430 BC, gave it a medical slant, referring to physical syndromes (illnesses) that occurred in particular places and times. After the discovery of bacteria in the nineteenth century, people began to use the term to refer to specific diseases, as in epidemics of cholera. More recently, the word has been used to refer to more cases than expected, both of very specific diseases, such as hemolytic uremic syndrome caused by E. coli O157:H7, and general syndromes, such as obesity.
This brings us back to the question of expectations. Every year, we expect a certain number of cases of say, influenza A. When we get more than we expect, or we are faced with a new variation of the same old thing, we call it an epidemic. Some diseases, such as West Nile virus disease and Lyme disease, start as epidemics. They surprise us. But after a few years, we get used to them, and we think of them as troublesome, tiresome, endemic. They now belong here, wherever that “here” may be. The words we use to describe these disease patterns are both descriptive and a way to catch—or divert—our attention. Why, some might ask, are there more cases than we expect? How and why have our expectations changed?
Multi-country outbreaks of various strains of food-borne Salmonella, noroviruses, and E. coli are regularly reported around the world. These are rarely called epidemics. And almost never called pandemics. These are the “normal” costs of producing lots of food, or so we are led to believe. If nothing else, the language we use should tell us something about our expectations in the twenty-first century.
Pandemics are a step beyond epidemics, at least in terms of numbers. The World Health Organization (WHO) defines a pandemic as “an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people.” The classical definition includes nothing about severity: a disease may become pandemic without being a serious killer. A serious killer disease, even one appearing in many different parts of the world, may not necessarily be classified as a pandemic.
SARS, for instance, was never officially declared a pandemic. Our global alarm was that it might become a pandemic, and was intensified by a general confusion about the non-human origins of most human diseases. Similarly, HIV/AIDS spread around the world in ways that some of us could only describe as a pandemic. In fact, although many agencies and researchers do call it a pandemic, WHO refers to it as a “global epidemic.” Before 2020, the only WHO-declared pandemics since 1900 were in 1918, 1958, 1968, and 2009. All were influenza, and all our guidelines for pandemic response are based on influenza.
If you find this confusing, you are not alone.
Influenza viruses afflicting millions of people annually cross international boundaries in temperate southern and northern hemispheres. However, these “seasonal epidemics” are not called pandemics. An influenza pandemic is a global outbreak of a new influenza A virus, such as the H1N1 strain associated with the 2009–10 pandemic. According to the Centers for Disease Control and Prevention (CDC), “Pandemics happen when new (novel) influenza A viruses emerge which are able to infect people easily and spread from person to person in an efficient and sustained way.” This is why, when pandemics are first described, we often see the word “novel” or “variant” or just a little “n” or “v” in front of the name.
In 2009, WHO published a document called “Pandemic Influenza Preparedness and Response,” which offers more specific guidance. This guidance document described a model with six pandemic phases. The model starts with Phase One, in which other animals, but no people, are infected, and finally arrives at Phase Six, the Pandemic Phase, in which there is “increased and sustained [human-to-human] transmission in the general population.” To be considered a true pandemic, however, this human-to-human transmission can’t just be inside one country, or even in two countries in the same WHO administrative region, but must also be in at least one country in a different administrative region.
After that, waves of the disease go around the world, but fewer people get sick and die with each subsequent wave, either because humans have built up immunity or because the agent, defying creationists, evolves through the processes of mutation and natural selection. In this case, only those with milder forms of the disease survive long enough to pass it on to others, and hence the agent moves in with our species to a longer, gentler, more sustainable life.
In 2017, WHO published another guide, called “Pandemic Influenza Risk Management.” This guide is not a planning document. It is intended to “manage disaster risks” and to help countries assess risks so that they can make more informed decisions. This document, which appears to be the one that WHO used during the SARS-COV-2 pandemic, only shows four phases: Interpandemic, Alert, Pandemic, Transition and then—wait for it, another Interpandemic phase. Note that this document assumes that whenever we are not in a pandemic, we are between pandemics, as we are between ice ages. Although they were designed to manage influenza in humans, WHO phases can be applied to all infectious diseases. There is no non-pandemic phase in our future. We have always lived between pandemics and we always will.
I will remind you (and me), here, that the word “pandemic” does not imply severity. The emergence of H1N1 in pig populations and its spillover into humans appeared, at least at first, to be an example of this. In 2009 this new influenza virus was reported from Mexico and spread very rapidly into an officially declared global pandemic in just a few months. For both scientists and just plain folks, the whole thing was befuddling. Was this serious? Was it real? First bird flu. Now swine flu. Really?
To the relief and puzzlement of many, the new virus seemed to result in a human disease no more, or less, serious than the “normal flu.” Admittedly, “normal” influenza infects millions and kills thousands annually. Still, when, in June 2009, WHO declared that the spread of H1N1 was a pandemic, some of us were less than alarmed. When virologists were able to rapidly incorporate the novel virus into the annual flu vaccination package, I actively supported vaccination programs. My general view of vaccinations is that they are there more to protect others than to save myself. Whatever side effects the vaccine might incur were part of my commitment to keeping the people around me and in the community healthy. I believed then—as I still do—that many anti-vaxxers are driven by selfishness. As an admittedly privileged, and sometimes smug, white male Canadian, this “me-me-me” business was not something to which I aspired. Still, I had my moments of cynicism. Even as WHO explained pandemics to the general public, and rolled out their six-phase pandemic preparedness plan, I devised my own version of the phases of what I called pandemic panic. My categories started at a pre-panic Phase One, a kind of who-cares phase, in which infection was transmitted among animals in poor countries, then moved into an early panic phase, characterized by moral outrage, in which European and North American tourists returned home with stories about sick dogs or children in the streets. The highest levels of panic and depression among European and American officials, who usually lead the charge on responding to these emerging diseases, involved sick wealthy white people and corporate financial losses on the stock market.
By August 2010, when the pandemic was declared over, and WHO announced that H1N1 had settled into the “typical seasonal patterns,” the new virus had officially killed 18,500 people. The mathematical models used to follow seasonal influenza suggested actual deaths from H1N1 ranged between about 150,000 and 575,000. These numbers are not those we might find with Ebola, but they are not trivial.
On the face of it, the “why” questions of the H1N1 pandemic appeared, at first, to be straightforward. The initial explanation was that the virus originated in commercially raised pigs in Mexico. Later, based on comparisons between the genetic composition of the 2009 virus and other swine influenza viruses circulating in the region, researchers discovered that the movement of viruses from Eurasia and the United States into Mexico closely followed the direction of the global trade of live swine.
Pigs were raised in large-scale operations in Mexico for the North American market for reasons similar to those used for large-scale poultry production. Mexico (and many other countries) offered somewhat relaxed labor laws and low-cost workers. An infected farm worker, receiving low wages and with no paid sick leave or health insurance, would have every incentive not to stay home even when seriously ill. Under these inequitable social and labor conditions, the virus would have been transmitted back into the pigs in a positive feedback cycle. An obvious measure to prevent the spread of the virus would have been for all countries importing pigs from these farms to require them to have paid sick leave and health insurance for their workers, and to meet minimum standards of hygiene.
In one sense, every death is expected and tragic. Optimism about technological breakthroughs notwithstanding, death is, and will remain, the usual course of events. The world could not unfold as it should if we did not all, sooner or later, die. This eventuality is what gives us despair even as it opens the possibility of a better future for our grandchildren. Those of us of colonial descent, however, have come to expect that our deaths will occur later in life, by heart attacks, cancer, suicide, or car accidents, not viruses spread by chickens, pigs, or bats, for goodness’ sake.
There may be a measure of poetic justice in the idea that a global pandemic could come from chickens or bats. However, what we should be wary of is the pontifications and strutting of half-cocked experts and autocrats, like those who hijacked the global narrative after 9/11. We who are citizens of industrial societies have been the ones who called for a chicken in every pot, using every pork-barrel political maneuver at our disposal. In our conquest of hunger and pursuit of obesity, we were the ones who pushed for economies of scale in agriculture, which not only brought down the consumer price of good protein but also created vast brewing vats for a multitude of infectious microbes. Chickens and pigs, the two fastest-growing livestock populations in the history of the world, have been on the front line of our battles against nature and hunger—and our fanatical obsession with personal health, low taxes, and the economics of me-ism.
This, then, is the revenge of the pawns; the foods we eat are the frontline messengers from a beleaguered biosphere to cocky human beings. So far, at least with regard to avian and swine influenzas, the general response has been to centralize control and depopulate the barns, which is akin to shooting the messengers. If we want to stay around in a convivial world, our species shall have to do better; we shall have to come to some accommodation with the kings and queens and bishops hiding in the back row. This is not a battle to win. The best we can hope for is an uneasy, mutually respectful, mutually wary conversation.