Editorial commentary: forecasting when, where, and possibly why outbreaks are likely to occur.


For centuries, infectious disease outbreaks have influenced not only geopolitical events and human migration [1] but also linguistic patterns and the development of different cultures [2]. Infectious diseases were the major drivers of morbidity and mortality throughout the world. However, over the past century, infectious diseases have been surpassed by chronic diseases in terms of their impact on morbidity and mortality: chronic diseases now cause 63% of deaths worldwide [3]. But not all parts of the world have benefited from the dramatic reductions in the morbidity and mortality attributable to infectious diseases. High-income countries have observed the greatest reductions. In many of these countries, decreases in infectious diseases were observed before major medical developments like the introduction of vaccines and antimicrobials. Instead these health improvements coincided with the widespread availability of clean water and improved sanitization, changes associated with economic development. In the current issue of Clinical Infectious Diseases, Chan et al explore the associations between measures of economic development and the likelihood of infectious disease outbreaks [4]. Considering multiple, easily obtained measures of economic development, Chan and colleagues find that the percentage of children vaccinated for measles and the number of telephone lines per 100 people are statistically associated with lower rates of infectious outbreaks. Here outbreaks are defined as either the first country to report cases, or, if that cannot be determined, the country with the most cases. However, it is important to stress that most of the variables they considered (eg, primary school enrollment, paved road density) are highly correlated with each other, and also with a “human development index” obtained from the United Nations [5]. Thus, regardless of the variables considered, the authors convincingly show that outbreaks can be partially explained and anticipated using publicly available information related to economic development and poverty. Importantly, Chan and colleagues, by focusing on forecasting, instead of merely reporting associations, move in the direction of understanding not only when and where outbreaks are most likely to occur, but maybe even why they occur. An equally interesting finding of this paper relates to the factors not associated with a decrease in outbreaks. For example, the authors found that democracy was not an important predictor of infectious disease outbreaks in their model. Why? Findings from other investigations may help explain this result. Previous economic research has shown that “rule of law” (ie, fair implementation of laws and settling of disputes) is strongly associated with economic growth regardless of the political system [6]. In other words, democracy alone might not be enough. Indeed, in 1755 Adam Smith said that “a tolerable administration of justice” is needed “to carry a state to the highest degrees of opulence.” Three hundred years later, this same intervention may, at least in part, help decrease the occurrence of outbreaks. Another interesting finding is that although the percentage of children vaccinated against measles was significant in their model, public health expenditure levels in general were not associated with a decrease in outbreaks. Perhaps, as the authors propose, health-associated financial aid to low-income countries may “displace” local spending on public health. They also suggest that in some cases aid may be used for unintended purposes. Received 5 October 2012; accepted 15 October 2012; electronically published 1 November 2012. Correspondence: Philip M. Polgreen, MD, Division of Infectious Diseases, Dept of Internal Medicine, Carver College of Medicine, Dept of Epidemiology, College of Public Health, University of Iowa Hospitals and Clinics, 200 Hawkins Dr, Iowa City, IA 52252 (philip-polgreen@uiowa.edu). Clinical Infectious Diseases 2013;56(4):525–6 © The Author 2012. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. permissions@oup.com. DOI: 10.1093/cid/cis930


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