Introduction

Emerging pathogens and the emerging infectious diseases they cause are, by now, almost received wisdom, with scores of books, conferences, and even entire journals devoted to them. The modern interest in emerging infectious diseases can be traced back to the 1990s when, in the wake of what has been labeled the “Age of Receding Pandemics” (named as such due to the shift in causes of mortality away from infectious diseases), ¹ a seemingly unending stream of unknown and rare infections—as well as many thought to have been already vanquished or adequately controlled—rose to a level that could only be ignored at humankind's peril, as gruesomely illustrated by the death toll resulting from the emergence of HIV.

When examined as individual events, emerging infectious disease outbreaks often appear as mere ripples in an ocean of endemic and chronic diseases—particularly as sensationalistic press headlines recede and public attention wanes—and there is a tendency to lose sight of what this special class of diseases truly represents. Many endemic diseases (eg, cancer, heart disease) have simply become a fact of life in many populations. Despite now being responsible for the plurality of deaths globally, ² morbidity and mortality associated with these diseases have been accepted as routine, and healthcare and society have adapted to their omnipresence.

Emerging infectious diseases, on the other hand, share almost none of these characteristics. By their very nature, emerging infectious disease events are acute and disruptive, inciting calamity and stoking panic. As evidenced by recent outbreaks and epidemics of Ebola, SARS, MERS, and Zika, these events can serve as the impetus for sweeping changes in how we, as a global society, approach infectious disease preparedness and response and radically reshape how we perceive risk, with potentially destabilizing social, political, and economic effects on top of the morbidity and mortality directly associated with the disease itself.

That these infectious disease emergencies occur with relative frequency is not surprising to those with knowledge of the field and of human history. This fact often makes it frustrating to perpetually relearn lessons from previous events as a myriad of 21st-century factors such as the anti-vaccine movement, the threat of bioterrorism, antimicrobial resistance, and global trade and travel bring these events to light on an almost daily basis. As our late founder and former editor-in-chief, the architect of WHO's smallpox eradication program, DA Henderson said, “In the 21st century, the potential threat of new and emerging infectious diseases has changed. … We must remember that there is a constantly mutating diverse microbiota throughout the world. It regularly throws off new variants.” ³

In this special feature in Health Security, we have assembled 8 pieces from across the spectrum of emerging infectious diseases that aim to reinforce the unique status of emerging pathogens and the preparedness activities required to keep them at bay, with a particular attention to the impact that these infections have on the overall health security of populations.

The field of emerging infectious disease is one that naturally integrates with biosecurity and health security, as the often-explosive spread of these pathogens creates a necessity for world leaders to confront these threats through action, engagement, and, crucially, through public risk communication that provides clarity, reassurance, and actionable guidance. The study of emerging infectious diseases may begin with the fundamental understanding of microbes' biological and pathophysiological mechanisms, but it quickly expands to include applied research such as how to detect and combat these infections, in both the individual and the community, and how to best protect healthcare workers and the public against infection. With subject matter ranging from Ebola to Zika and risk assessment to hospital preparedness and articles drawn from the United States, Pakistan, and Canada, this issue will hopefully find a large domestic and international audience that will not only learn from these articles but also employ them as springboards for further research and distill the information to improve the management of these diseases in their individual locales.

In 1992, the Institute of Medicine Committee on Emerging Microbial Threats to Health, led by the late Nobel Laureate Joshua Lederberg, noted that “there are many steps that scientists, educators, public health officials, policymakers, and others can and should be taking to improve our odds in this ongoing struggle. With diligence and concerted action at many levels, the threats posed by infectious diseases can be, if not eliminated, at least significantly moderated.” We offer these articles with that aim in mind. ⁴