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This volume is based on the National Academy of Sciences' colloquium entitled "Changes in Human Ecology and Behavior: Effects on Infectious Diseases." The articles appearing in these pages were contributed by speakers at the colloquium and have not been independently reviewed. Any opinions, findings, conclusions, or recommendations expressed in this volume are those of the authors and do not necessarily reflect the views of the National Academy of Sciences.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences.
Library of Congress Cataloging-in-Publication Data
Infectious diseases in an age of change: the impact of human ecology and behavior on disease transmission / Bernard Roizman, editor
p. cm.
Includes bibliographical references and index.
ISBN 0-309-05136-3
1. Communicable diseases. I. Roizman, Bernard, 1929-[DNLM: 1. Communicable Diseases—epidemiology. 2. Risk Factors. 3. Social Environment. WC 100 14156 1995]
RA643.1654 1995
616.9—dc20
DNLM/DLC
for Library of Congress 94-31151
CIP
Copyright 1995 by the National Academy of Sciences. All rights reserved.
Printed in the United States of America
Preface
… it is not inconsistent with respect to personal freedom to attempt to create an environment which encourages people to do what is good for them and to avoid what is bad.
Thomas McKeown The Origins of Human Disease Blackwell, Oxford, United Kingdom, 1988 p. 215.
The two key factors which affect the spread of infectious diseases in the human community other than the nature of the infectious agent are human ecology and behavior. Although some aspects of the impact of the resulting infections are similar since both result in disease, the processes by which these human activities lead to increased risk of infectious disease are quite different.
The agents of infectious diseases do not arise de novo in each infected individual by spontaneous generation. For the most part, they are transmitted from one species to another or from one individual of a species to another member of the same species. To survive, infectious agents must be successful in maintaining themselves in their chosen, susceptible population. There are many determinants of success, but undoubtedly contact between the infected and the susceptible populations is a major determinant of the frequency of transmission. Furthermore, when a human population comes in contact with a new transmissible agent, or with a previously isolated human population, new
Bernard Roizman is the Joseph Regenstein Distinguished Service Professor of Virology at the University of Chicago.
James M. Hughes is director of the National Center for Infectious Diseases at the Centers for Disease Control and Prevention, Atlanta, Georgia.
infectious agents are likely to enter the human community. These simple rules have been known for many years. They accounted for the spread of measles, smallpox, influenza, and bubonic plague in the centuries past. The principle that human ecology affects the incidence and patterns of infectious diseases is not only accepted but has been credited with playing a major role in the rise and fall of nations in human history (1). The focus of attention of the articles in this volume is on two aspects of changes in ecology. The first concerns the spread of infectious agents resulting from the human migrations from regions of high disease incidence to low incidence, from cities to forested suburban areas, etc. The second concerns the rise and spread of agents resistant to drugs designed to arrest their multiplication.
Only recently, however, have we become fully aware of the global impact of the changes in human behavior on infectious diseases. At first glance, "changes in human behavior" implies changes in sexual behavior, and in fact, increases in the number of sexual partners accounts for the increased incidence of sexually transmitted diseases. We may add failure to self administer available drugs to arrest the development and spread of drug-resistant, non-sexually transmitted agents such as Mycobacterium tuberculosis, and the role of immunosuppressive medical treatments which may predispose patients to serious infections with agents considered relatively innocuous for immunocompetent individuals.
The increase in the incidence or severity of infectious maladies has led to the recognition of emerging infectious agents and diseases; these have been described in numerous reports and publications (e.g., 2–4). It is relevant to note that some 10 to 15 years ago it was thought that most infectious agents of diseases had been identified and that the few agents still unknown played a role in diseases, like cancer, which manifested themselves many years after infection. Two events discredited this view. Foremost, the technology for identification of the presence of an infectious agent underwent dramatic developments and led to the identification of several hitherto unknown, but not novel agents of disease. No less important, however, was the fact that changes in human ecology and behavior increased the incidence or severity of diseases resulting in their recognition and subsequent investigation. The significance of the latter factor cannot be overstated. Improved surveillance to ensure a timely response to the effects of changes in ecology and behavior on human infectious disease will play a major role in reducing the human burden of infectious diseases (5). Control of infectious diseases is our goal. The lesson of history is that prevention of infectious diseases by prophylaxis or immunization will be only partially effective
in the absence of changes in human behavior and ecology. Syphilis, for example, is still rampant notwithstanding availability of inexpensive and effective therapy.
Effecting changes in human behavior and ecology pits the rights of the individual against the best interests of the society. The issues are not new. Carlo M. Cipolla's studies (6) of archival documents dealing with the plague which ravaged Tuscany in the middle of the seventeenth century are of particular interest. The plague was endemic in seventeenth-century Europe and its causes were not well understood. Diseases which spread through the population were thought to be caused by miasmas characterized by foul odors which clung to the environment and spread from person to person. The Florentine authorities established Health Magistrates whose task was to monitor the pesthouses to which the ill were brought, and to enforce quarantines. The quarantines were commonly disliked because they interfered with everyday life. By and large the Church assisted the Health Magistrates in enforcing procedures that were found empirically to minimize the spread of the plague. In a few instances conflicts arose. While the Health Magistrates had little doubt that religious processions kindled the spread of plague, the men of the Church fervently believed that processions and similar ceremonies had exactly the opposite effect. Cipolla recounts that in December of 1630 the Prior of the Monastery of St. Marco pressed for a religious procession in the face of opposition of the Health Magistrates. A compromise was finally worked out. The procession was held, but it was restricted to chosen members of the clergy, the Grand Duke and his court, and the Senators in their purple. The populace was excluded and access to the procession was blocked by horse guards. Even so, as Cipolla recounts, the streets were strewn with fragrant herbs, presumably to mask the odors through which the plague spread.
The Florentines of the mid-seventeenth century did not know of the role of bacilli, rats and fleas in the dissemination of the plague. While the basic premise was in error, they learned empirically of the need to control human behavior to reduce the impact of the epidemics. Over three centuries later, as this collection of scientific reports illustrates, we know the etiology of most infectious diseases affecting humans but we are far from being able to deal effectively with the factors which facilitate their transmission. Continuous research and dissemination of facts concerning the role of human behavior and ecology on the incidence and spread of infections may ultimately bring about the kind of environment sought by Thomas McKeown.
BERNARD ROIZMAN AND JAMES M. HUGHES
REFERENCES
1. McNeill, W. H. 1976. Plagues and Peoples. Garden City, N. Y.: Anchor Press/Doubleday.
2. Krause, R. M. 1992. The origin of plagues: old and new. Science 257:1073-1078.
3. Lederberg, J., Shope, R. E., and Oaks, S. C., eds. 1992. Emerging Infections: Microbial Threats to Health in the United States. Washington, D.C.: National Academy Press.
4. Morse, S. S., ed. 1993. Emerging Viruses. New York: Oxford University Press.
5. Centers for Disease Control and Prevention. 1994. Addressing Emerging Infectious Disease Threats: A Prevention Strategy for the United States. Atlanta: U.S. Department of Health and Human Services.
6. Cipolla, C. M. 1981. Faith, Reason, and the Plague in Seventeenth Century Tuscany. New York: W.W. Norton & Co.
Acknowledgments
The chapters collected in this book were presented at a colloquium held at the National Academy of Sciences on September 27 and 28, 1993. Several of the chapters, notably those by L. H. Miller, T. P. Monath, T. C. Quinn, and J. N. Wasserheit, have been updated. I am indebted to the National Academy of Sciences for its support and to Robert M. Chanock, James M. Hughes, Stanley Falkow, John LaMontagne, and Richard J. Whitley for their advice and involvement in the organization of the colloquium.
BERNARD ROIZMAN
Contents
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Lyme Disease: A Growing Threat to Urban Populations |
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Working Parents: The Impact of Day Care and Breast-Feeding on Cytomegalovirus Infections in Offspring |
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Changes in Human Ecology and Behavior in Relation to the Emergence of Diarrheal Diseases, Including Cholera |
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Dengue: The Risk to Developed and Developing Countries |
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Hepatitis Viruses: Changing Patterns of Human Disease |
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Population Migration and the Spread of Types 1 and 2 Human Immunodeficiency Viruses |
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Impact of Malaria on Genetic Polymorphism and Genetic Diseases in Africans and African Americans |
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Hospital-Acquired Infections: Diseases with Increasingly Limited Therapies |
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Evolution of Drug-Resistant Tuberculosis: A Tale of Two Species |
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Effect of Human Ecology and Behavior on Patterns of Sexually Transmitted Diseases, Including HIV Infection |
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Genital Human Papillomavirus Infection |
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Herpes Simplex Virus Infections of Women and Their Offspring: Implications for a Developed Society |
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Human Ecology and Behavior and Sexually Transmitted Bacterial Infections |
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Vaccines for Bacterial Sexually Transmitted Infections:A Realistic Goal? |
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Quest for Life-Long Protection by Vaccination |
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