The belief that many long-recognized chronic diseases are infectious in origin goes back to the mid-nineteenth century, when cancer was studied as a possible infectious disease. In the 1950s and 1960s, much biomedical research was directed, unsuccessfully, at the identification of microorganisms purportedly causing a variety of chronic diseases. In recent years the picture has begun to change. One chronic disease after another has been linked, in some cases definitively, to an infectious etiology (e.g., peptic ulcer disease with Helicobacter pylori, cervical cancer with several human papillomaviruses, Whipple's disease with Tropheryma whippeli, Lyme arthritis and neuroborreliosis with Borrelia burgdorferi, AIDS with HIV). Evidence implicating microorganisms as etiologic agents of chronic diseases with substantial mortality and morbidity impact, including atherosclerosis and cardiovascular disease, diabetes mellitus, inflammatory bowel disease, and a variety of neurological and neuropsychiatric diseases, continues to mount.
Emerging infectious diseases are conceptualized as either newly identified or appreciated illnesses, conditions, or well-recognized diseases that are newly attributed to infection. Now, scientists are beginning to believe that a substantial portion of chronic diseases may actually be infectious.
While chronic diseases may be proportionally more important in industrialized countries, they actually take a significant toll throughout the world. In the next 25 years it is expected that chronic diseases of economically established countries, dominant among health issues, will increasingly become those of economically developing regions. In these areas of limited health care resources, newly identified infectious etiologies of chronic diseases, including those already known to enter a chronic state, such as tuberculosis and malaria, will acquire increasing importance. The substantial burden presented by chronic diseases of infectious etiology demands global attention and action.
Identifying and confirming an infectious cause of chronic disease is complicated by several factors:
- in some cases, microorganisms may act in a "hit and run" fashion, having disappeared by the time the disease process becomes apparent (e.g., Reiter's syndrome, Guillian Barré syndrome, rheumatic heart disease);
- infection may be latent at the time of diagnosis;
- acute, chronic, latent, or recurrent infections may be involved in pathogenesis;
- detection and culture of microbes in a variety of tissues may be difficult;
- multifactorial etiology, including environmental and genetic (host and microbe) factors;
- the lack of adequate methods to identify novel or rare microorganisms.
Recently-developed molecular and immunological techniques offer new ways to overcome these obstacles. These include representational difference analysis, gene-chip profiling of host and microbe, MHC tetramer technology, intracellular cytokine staining, proteomics, and many others. However, the application of new technologies also demands a database of epidemiologic clues to guide the research efforts. Coordination between basic and clinical scientists, pathologists, and epidemiologists is critical to the development of standardized specific case definitions and specimens, and comparable methods of analysis. Moreover, there needs to be a systematic strategy for defining the nature and scope of the challenge, and for meeting the challenge.
In an effort to identify cross-disciplinary aspects of the challenge of infectious etiologies of chronic diseases, including inflammatory syndromes and cancer, the Institute of Medicine's Forum on Emerging Infections will host a two-day workshop on October 21–22, 2002. The workshop, Linking Infectious Agents and Chronic Diseases will explore the factors that drive infectious etiologies of chronic diseases to prominence, and will seek to identify more broad-based strategies and research programs that need to be developed. The goals of the workshop are to:
- Review the range of pathogenic mechanisms and diversity of etiologic microbes and chronic diseases, including inflammatory syndromes and cancer;
- Explore trends, advances, and gaps in collaborative research on diagnostic technologies, and their integration into epidemiologic studies and surveillance;
- Identify chronic diseases and syndromes that warrant further investigation;
- Identify research needed to clarify the etiologic agents and pathogenic mechanisms involved in chronic diseases, screening for multiple potential agents of the same outcome, and considering that one microbe might induce multiple syndromes;
- Identify the principal bottlenecks and opportunities to detect, prevent, and mitigate the impact of chronic diseases on human health against the overall backdrop of emerging infections;
- Consider the benefits and risks of early detection and prevention of chronic diseases caused by infectious agents.
The issues pertaining to these goals will be addressed through invited presentations and subsequent discussions, which will highlight ongoing programs and actions taken, and will also identify the most vital needs in this important area.
|