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Andrew T Price-Smith, Contagion and chaos: disease, ecology, and national security in the era of globalization , Cambridge, MA, MIT Press, 2009, pp. x, 281, £30.95, $48.00 (hardback 978-0-262-16248-7), £15.95, $24.00 (paperback 978-0-262-66203-1).

“Health is the fulcrum of material power, and therefore it is central to the interests of the modern sovereign state” (p. 1). With this statement, Andrew Price-Smith begins his recent extension of republican security theory, Contagion and chaos: analysing the effects of infectious diseases on a nation's economy, security, and international influence. The author hopes to encourage interdisciplinary discourse, “bridging the epistemic schisms that have deepened over the decades as a result of disciplinary specialization” (p. 4). 
 
Price-Smith, an assistant professor in the Department of Political Science and Director of the Project on Energy, Environment, and Global Security at The Colorado College, has written about these concepts previously in The health of nations: infectious disease, environmental change, and their effects on national security and development (Cambridge, MA, MIT Press, 2002) and is the editor of Plagues and politics: infectious disease and international policy (2001). The book being reviewed is based on work done while the author was with the Program on Health and Global Affairs, Centre for International Studies, University of Toronto, where he completed his PhD. 
 
The author proposes five hypotheses to be explored in this volume where he applies republican security theory. First, epidemic disease may exacerbate prosperity, cohesion, and security of countries. Second, emergence of novel pathogens may promote conflict between countries. Third, criteria of pathogens that threaten national security include: lethalness, transmissibility, fear, and potential for economic damage. Fourth, warfare contributes to the burden of infectious diseases; and fifth, health security is grounded in republican theory and therefore integrally connected to national security. Price-Smith devotes chapter 1 to the theory of republicanism, reaching back to ancient Greece and Hellenic sources. While this development may be compelling to an academic consideration of the topic, public health practitioners will become impatient with the relatively dry historical development. 
 
To support the second hypothesis, in chapter 2 the author uses the plague (1348), smallpox, yellow fever, and the 1918–1919 influenza pandemic to illustrate the theory of the impact of epidemic disease on sovereign states. This theoretical development is followed by chapters that consider influenza, HIV/AIDS, mad cow disease, and SARS. The volume concludes with chapters on the effect of war on disease, and the interrelationship among health, power, and security. In 1995, Dr David Satcher introduced a new journal Emerging Infectious Diseases with an articulation of major aetiologic agents and the burden of emerging and re-emerging infectious diseases; Price-Smith’s third hypothesis extends these criteria to include fear and potential for economic damage. 
 
As with any interdisciplinary study, “disciplinary specialists” must be educated to another's language, vocabulary, and thinking, then deciding to accept the purported linkage. The writing style is that of a social scientist, conversational, with several footnotes and references. As a consequence, many statements lack the precision and level of evidence usually required for medicine and public health. An example is the author’s lack of distinction between incidence and prevalence. In a discussion of UNAIDS 2006 Report on the global AIDS epidemic, the author states, “… UNAIDS prefers to emphasize the point that the epidemic appears to have slowed its expansion”. While it is true that the overall incidence rate (number of people newly infected with HIV) is believed to have peaked in the 1990s, UNAIDS states that “Favourable trends in incidence in several countries … related to changes in behaviour and prevention programmes … [and] rising AIDS mortality have caused global HIV prevalence (the proportion of people living with HIV) to level off. However, the numbers of people living with HIV have continued to rise, due to population growth and, more recently, the life-prolonging effects of antiretroviral therapy” (UNAIDS, Report on the global AIDS epidemic, 2006). In fact, in 2008, the agency stated, “The rate of new HIV infections has fallen in several countries, although globally these favourable trends are at least partially offset by increases in new infections in other countries” (ibid., 2008). 
 
Referencing is somewhat uneven. For example, in his development of the fourth hypothesis in chapter 7, ‘War as a “Disease Amplifier”’, Price-Smith draws heavily (and appropriately) on the work of Andrew Cliff and Matthew Smallman-Raynor, but neglects the extremely relevant work by Barry S Levy and Victor W Seidel, War and public health (2nd ed., Oxford University Press, 2008). The book’s primary audience is students and practitioners of public policy. In light of the recent swine influenza pandemic and the World Health Organization’s proposal to “redefine” the criteria for a pandemic, do we remain unconvinced of the association between infectious disease and political stability? If so, what will it take to convince policy makers of this connection? The call in Contagion and chaos is to bridge the gap between the natural and social sciences to acknowledge their causal dependence.