Emerging Infectious Determinants of Chronic Diseases

Siobhán M. O'Connor; Christopher E. Taylor; James M. Hughes

Disclosures

Emerging Infectious Diseases. 2006;12(7):1051-1057. 

In This Article

Abstract and Introduction

Abstract

Evidence now confirms that noncommunicable chronic diseases can stem from infectious agents. Furthermore, at least 13 of 39 recently described infectious agents induce chronic syndromes. Identifying the relationships can affect health across populations, creating opportunities to reduce the impact of chronic disease by preventing or treating infection. As the concept is progressively accepted, advances in laboratory technology and epidemiology facilitate the detection of noncultivable, novel, and even recognized microbial origins. A spectrum of diverse pathogens and chronic syndromes emerges, with a range of pathways from exposure to chronic illness or disability. Complex systems of changing human behavioral traits superimposed on human, microbial, and environmental factors often determine risk for exposure and chronic outcome. Yet the strength of causal evidence varies widely, and detecting a microbe does not prove causality. Nevertheless, infectious agents likely determine more cancers, immune-mediated syndromes, neurodevelopmental disorders, and other chronic conditions than currently appreciated.

Introduction

Infectious agents have emerged as notable determinants, not just complications, of chronic diseases. Not infrequently, infection may simply represent the first misstep along a continuum from health to long-term illness and disability. Preventing or treating infection or the immune response to infection offers a chance to disrupt the continuum, avoiding or minimizing a chronic outcome. To capitalize on these opportunities, clinicians, public health practitioners, and policymakers must recognize that many chronic diseases may indeed have infectious origins.

A diverse spectrum of agents, pathways, outcomes, and co-factors characterize the already well-established causal associations. Together, this group affects all populations around the globe—regardless of country, region, race/ethnicity, socioeconomic status, or culture. Expectations are that additional etiologic relationships will emerge over the coming decades, influenced by ever-evolving populations, ecology, and economies as well as by advances in science and technology.[1,2] The true potential to avoid or minimize chronic disease by preventing or treating infections may yet be substantially underestimated.

Controlling infectious diseases remains paramount to the health and well-being of persons and populations worldwide. The breakdown of public health and prevention measures leads to the resurgence of old and new microbial threats. Nevertheless, implementing and maintaining infection control measures is shifting disease patterns, so that today chronic diseases represent the major health burden of established economies (>90 million people in the United States) and are a rapidly growing burden in developing economies (http://www.cdc.gov/nccdphp/overview.htm).[3] This fact implies that preventing or mitigating chronic diseases of infectious etiology could have considerable positive impact on global and domestic health. Add to this the potential benefits of minimizing infections that influence the morbidity of preexisting chronic conditions. The result is a tremendous opportunity to reduce long-term illness and disability worldwide by maximizing infection prevention and control.

In this perspective, we focus on (non-HIV) infectious determinants of chronic diseases, in which ≥1 infectious agent(s) causes, precipitates, or drives the chronic disease or its long-term sequelae. Expanding on previously published discussions,[4,5,6,7] we outline the causal connections and reasons for their emergence, describing the breadth of the field and the diverse pathways from microbial exposure to chronic disease. Lastly, we present a complex systems framework for the multifactorial interactions that often lead to long-term sequelae, citing current and emerging opportunities for research to prevent chronic diseases of infectious etiology and discussing the potential impact of these benefits.

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