Emerging Infectious Diseases: a 10-Year Perspective from the

Abstract and Introduction

Abstract

Although optimists once imagined that serious infectious disease threats would by now be conquered, newly emerging (e.g., severe acute respiratory syndrome [SARS]), reemerging (e.g., West Nile virus), and even deliberately disseminated infectious diseases (e.g., anthrax bioterrorism) continue to appear throughout the world. Over the past decade, the global effort to identify and characterize infectious agents, decipher the underlying pathways by which they cause disease, and develop preventive measures and treatments for many of the world's most dangerous pathogens has resulted in considerable progress. Intramural and extramural investigators supported by the National Institute of Allergy and Infectious Diseases (NIAID) have contributed substantially to this effort. This overview highlights selected NIAID-sponsored research advances over the past decade, with a focus on progress in combating HIV/AIDS, malaria, tuberculosis, influenza, SARS, West Nile virus, and potential bioterror agents. Many basic research discoveries have been translated into novel diagnostics, antiviral and antimicrobial compounds, and vaccines, often with extraordinary speed.

Introduction

Infectious diseases have been an ever-present threat to mankind. From the biblical plagues and the Plague of Athens in ancient times, to the Black Death of the Middle Ages, the 1918 "Spanish Flu" pandemic, and more recently, the HIV/AIDS pandemic, infectious diseases have continued to emerge and reemerge in a manner that defies accurate predictions.^[1,2,3]

The past 10 years (1994-2004) have been no exception, as many new and reemerging microbial threats have continued to challenge the public health and infectious disease research communities worldwide. Since 1994, when Emerging Infectious Diseases made its publication debut, significant strides in the global fight against the HIV/AIDS pandemic have been made. The infectious disease community has confronted several other newly emerging pathogens, such as the severe acute respiratory syndrome-associated coronavirus (SARS-CoV), henipaviruses (Hendra and Nipah), and, most recently, avian influenza viruses that have caused illness and deaths in humans with the threat of evolution into a pandemic.^[1,2,3] In addition, historically established infectious diseases, such as West Nile fever, human monkeypox, dengue, tuberculosis, and malaria have reemerged or resurged, sometimes in populations that previously had been relatively exempt from such affronts. Over the past decade, strains of common microbes such as Staphylococcus aureus and Mycobacterium tuberculosis have continued to develop resistance to the drugs that once were effective against them.^[1,2,3,4] Such antimicrobial-resistant microorganisms, which defy conventional therapies and pose a threat to public health, underscore the need for a robust pipeline of new antimicrobial agents based on innovative therapeutic strategies, new vaccines, and other preventive measures.^[3,4]

Perhaps most disturbing, the United States has recently experienced a deliberately spread infectious disease in the form of 22 anthrax infections, including 5 anthrax-related deaths resulting from bioterrorism in 2001.^[5] These cases were accompanied by widespread psychological sequelae and societal and economic disruptions.

These emerging and reemerging infectious diseases are superimposed on a substantial baseline of established infectious diseases. Although annual deaths and lost years of healthy life from infectious diseases have decreased over the past decade, the worldwide impact from infectious diseases remains substantial. Overall, infectious diseases remain the third leading cause of death in the United States each year and the second leading cause of death worldwide.^[6] As shown in Figure 1, of the estimated 57 million deaths that occur throughout the world each year, ≈15 million, >25%, are directly caused by infectious diseases. Millions more deaths are due to secondary effects of infections.^[6]

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Figure 1.

Leading causes of death worldwide (estimates for 2002). Nearly 15 million (>25%) of the 57 million annual deaths worldwide are caused by infectious disease.^[6]

Infectious diseases also lead to compromised health and disability, accounting for nearly 30% of all disability-adjusted life years (DALYs) worldwide (1 disability-adjusted life year is 1 lost year of healthy life).^[6] Infectious diseases that contribute to the nearly 1.5 billion total DALYs each year are categorized in Figure 2.

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Figure 2.

Leading causes of disability-adjusted life years (DALYs) due to infectious and parasitic diseases (2002 estimates). Lower respiratory infections, HIV/AIDS, diarrheal diseases, and malaria are among the infectious diseases that contribute to the most DALYs each year throughout the world.^[6]

In the United States, the Centers for Disease Control and Prevention has devised strategies to prevent, monitor, and contain disease outbreaks. Within the National Institutes of Health, the National Institute of Allergy and Infectious Diseases (NIAID) is the lead agency for infectious disease research.

Over the past decade, the NIAID budget has quadrupled; spending on emerging infectious diseases has increased from <$50 million in 1994 to >$1.7 billion projected for 2005, a boost due in large part to increases in funding for biodefense research (Figure 3). NIAID-supported intramural and extramural investigators have contributed substantially to the global effort to identify and characterize infectious agents, decipher the underlying pathways by which they cause disease, and develop preventive measures and treatments for many of the world's most dangerous pathogens. This review briefly highlights some of the research strides made by NIAID-supported investigators during the past decade in preventing and combating emerging and reemerging infectious diseases threats.

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Figure 3.

Budget of the National Institute for Allergy and Infectious Disease (NIAID), FY1994-2005. The overall NIAID budget rose from $1.06 billion in FY1994 to $4.4 billion (estimated) in FY2005. Funding for emerging infectious diseases rose from $47.2 million in FY1994 to $1.74 billion in FY2005 (est.).

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