What Is an Epidemic?

What Is an Epidemic? Currents in Contemporary Misuse of the word “epidemic” has nature and infectivity of the causal become an epidemic. In this note I agent, its mode of transmission, Bioethics examine several accounts of what the degree of preexisting and newly it means to be an epidemic, explore acquired immunity, etc.”4 This defini- what I take to be the motivation for tion is clear and concise, and it hints Jonny Anomaly over-extending the term, and explain at why epidemics occur and how they why I think we should use it in a more evolve. However, just 15 years later, careful way. the 3rd edition of the Oxford Com- panion to Medicine reflects a newer Epidemics, Old and New and less helpful use of the term: “An The term “epidemic” can be traced epidemic is the occurrence of num- back to Hippocrates, and it appears at bers of cases of a disease clearly above least three times in his brief book, Of normal expectations.”5 References to the Epidemics, which is mainly a col- infection and duration are dropped, lection of medical case descriptions.1 though an above normal rate of dis- In each instance, Hippocrates uses ease remains as a criterion. the term to describe seasonal out- Other dictionaries and textbooks breaks of infectious diseases, though have made further changes, includ- he knew little about the etiology of ing dropping disease as a necessary infection.2 For more than two mil- condition, so that many now consider lennia, the term continued to be used an epidemic anything that negatively to indicate a sudden surge in disease, impacts the health or welfare of a or symptoms of disease, in a popula- large number of people in a popu- tion. Over time, it evolved to refer to lation.6 In some cases, the primary single diseases rather than clusters of definition is confined to infectious diseases or symptoms, but the essen- disease, but the secondary one covers tial meaning remained remarkably all unexpected adverse events that constant for over two thousand years. affect a population. For example, the According to the Oxford English dic- Oxford Dictionary Online includes tionary, the primary definition of epi- as a secondary definition: “a sudden, demic continues to be “a widespread widespread occurrence of a particu- occurrence of an infectious disease in lar undesirable phenomenon” and a community at a particular time.”3 lists “an epidemic of violence” as an Although vague, this account nicely example of this sense of the term.7 captures the common thought that I will argue that the newer mean- epidemics have something to do with ing of “epidemic” suffers from three a spike in infectious disease in a par- main problems: it lacks precision ticular population. and explanatory power, it is politi- An even more precise account is cally controversial, and it contributes found in the first edition of the Oxford to the increasingly common percep- Companion to Medicine, which tion of epidemiology (which began About This Column defines epidemic as “an outbreak of as the study of epidemics) and public disease such that for a limited period health (which began as the branch of Mark A. Rothstein serves as the of time a significantly greater number medicine charged with treating and section editor for Currents in Contem- of persons in a community or region preventing epidemics) as fields of porary Ethics. Professor Rothstein is are suffering from it than is normally study with no clear mission or unique the Herbert F. Boehl Chair of Law the case…The extent and duration of domain. and Medicine and the Director of the an epidemic are determined by the The first problem with the second- Institute for Bioethics, Health Policy interaction of such variables as the ary sense of epidemic is that it is too and Law at the University of Louisville School of Medicine in Kentucky. ([email protected]) Jonny Anomaly, Ph.D., is affiliated with the Duke/UNC program in philosophy, politics & economics. 2 journal of law, medicine & ethics Jonny Anomaly inclusive to pick out a clear set of for vaccination rather than to accu- A third problem for the more issues. For example, if an epidemic rately depict the (likely) trajectory expansive account of epidemic is occurs whenever an unusually large of infection.9 Because epidemics and that epidemiologists – whose main number of people in a population pandemics caused by infectious dis- job is to discover, describe and are adversely affected by an event, ease can be scary events that inflict address epidemics – are not neces- we would have to include as epidem- large losses, most people are will - sarily well-placed to solve the many ics the increase in amputees during ing to make significant sacrifices to problems that fall within its scope, World War II, the uptick in children address them. The relevant sacrifices such as poverty, rape, and unem - who drown in rivers after Indian include foregoing freedom to travel ployment. Epidemiologists have no monsoons, and deaths and injuries to certain regions, and paying higher special expertise about what causes in Indonesia that occurred after the taxes to finance vaccination provi- these conditions, or how best to treat them. Instead, political scientists, economists, and psychologists are often better equipped to tell us I will argue that the newer meaning of how to improve employment pros- “epidemic” suffers from three main problems: pects, to create institutions that minimize violence, and so on. Of it lacks precision and explanatory power, it is course, epidemiologists should seek politically controversial, and it contributes to the out and synthesize knowledge from different fields. But there are good increasingly common perception of epidemiology reasons to be skeptical when we (which began as the study of epidemics) and are told that since violent crime is an epidemic, we should pay special public health (which began as the branch of attention to what epidemiologists medicine charged with treating and preventing say about its causes and solutions. There are perfectly good reasons, epidemics) as fields of study with no clear mission though, to listen to what traditional or unique domain. epidemiologists say about how to control the spread of infectious disease. massive 2004 tsunami. These are sion and disease surveillance pro- Communicating Risk medically important events, and in grams. If people are willing to make One of the main causes for concern some ways the resulting injuries were these sacrifices in order to diminish with an over-extended definition unexpected, but few would consider the threat of traditional epidemics, of “epidemic” is that it may become them epidemics. The main reason perhaps activists think they will be more difficult for physicians and seems to be that they are not caused more willing to endorse restrictive public health practitioners to explain by infectious agents. In all three cases laws or higher taxes to address obe- the relevant risks to non-specialists. there is a clear and common cause of sity, autism, and income inequality, Arguably the best way of communi- injury, but there is no vector or vehi- among other issues. cating the risks associated with an cle that transmits the medical event As public health professors Eileen epidemic is to explicitly describe its from one person to another. O’Neil and Elena Naumova have characteristics, such as the speed of The second problem with the argued, when “outbreak” and “epi- transmission, the number of new expansive account of epidemic is that demic” are used to describe problems cases, and the nature and severity of it tends to license a certain amount of like obesity and autism, the motiva- symptoms.11 It is also important to political manipulation.8 It is increas- tion may be to manipulate public classify a population-wide event as ingly common for well-meaning opinion in order to justify precon- either contagious or non-contagious. journalists, politicians and scientists ceived policies.10 This is a dangerous If the newer and broader definition to label global problems as “pandem- trend, and one that should be avoided of epidemic sticks, we should at least ics” (epidemics that cross borders) by scientists, and by scientific nomen- be honest about whether the condi- or “public health crises” in order to clature. When physicians, scientists tion is truly contagious, or whether draw attention to them. Even for and public health activists claim that it just happens to negatively affect a infectious disease, controversies “X is an epidemic,” the words con- large number of people. We might be have raged over whether to label jure images of a rapidly spreading tempted to say some conditions that recent outbreaks of Avian and Swine infectious disease that claims victims influence population health are “cul- flu as “pandemics.” Some suspect indiscriminately, not a steady uptick turally contagious,” rather than bio- that the main motivation for label- in the diagnosis of developmental logically contagious, but it is worth ing them pandemics is to raise public disabilities or an increased consump- remembering that even powerful awareness and government funding tion of carbohydrates. trends that use culture as a vector concussions and sports • fall 2014 3 JLME COLUMN are not literally contagious since peer The danger, of course, is that when Oxford, UK: Oxford University Press, pressure can be resisted. a real event occurs, the force of the 1986). 5. S. Lock, J. Last, and G. Dunea, The Consider adult obesity as a case word [“epidemic” or “outbreak”] has Oxford Companion to Medicine, 3rd ed. in point. Obesity has been labeled been exhausted and communication (Oxford, UK: Oxford University Press, an “outbreak” and an “epidemic,” about a catastrophic event may be 2001).

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