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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: Public Health / Epidemiology and Biostatistics
- Sprache: Englisch
Emerging Infectious Diseases
Emerging Infectious Diseases offers an introduction to emerging and reemerging infectious disease, focusing on significant illnesses found in various regions of the world. Many of these diseases strike tropical regions or developing countries with particular virulence, others are found in temperate or developed areas, and still other microbes and infections are more indiscriminate.
This volume includes information on the underlying mechanisms of microbial emergence, the technology used to detect them, and the strategies available to contain them. The author describes the diseases and their causative agents that are major factors in the health of populations the world over.
The book contains up-to-date selections from infectious disease journals as well as information from the Centers for Disease Control and Prevention, the World Health Organization, MedLine Plus, and the American Society for Microbiology.
Perfect for students or those new to the field, the book contains Summary Overviews (thumbnail sketches of the basic information about the microbe and the associated disease under examination), Review Questions (testing students' knowledge of the material), and Topics for Further Discussion (encouraging a wider conversation on the implications of the disease and challenging students to think creatively to develop new solutions).
This important volume provides broad coverage of a variety of emerging infectious diseases, of which most are directly important to health practitioners in the United States.
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CONTENTS
Tables and Figures
Preface
The Author
Acknowledgments
Part 1 : Introduction to Emerging Infectious Diseases
Chapter 1 : Infectious Diseases Past and Present
Major Concepts
History of Infectious Diseases
The Role of Infectious Diseases in the World Today
The Links Between Infectious Diseases, Poverty, and Civil Unrest
Emerging and Reemerging Infectious Diseases
Factors Contributing to the Emergence of New Infectious Diseases and the Spread and Evolution of Older Diseases
Timeline
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 2 : Of Microbes and Men
Major Concepts
Introduction
Infectious Agents: The Enemy Combatants
Genetic Information and the Making of Proteins: Preparing the Armament
The Immune Response: Humans Fight Back, Part One
Antimicrobial Agents: Humans Fight Back, Part Two
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Part 2 : Bacterial Infections
Chapter 3 : Lyme Disease
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 4 : Human Ehrlichiosis
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 5 : Bartonella Infections
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 6 : Group A Streptococci
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 7 : Escherichia Coli O157:H7
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 8 : Helicobacter Pylori, Ulcers, and Cancer
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 9 : Legionnaires’ Disease and Pontiac Fever
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 10 : Pulmonary Tuberculosis and Multidrug Resistance
Major Concepts
Introduction
History
The Disease
The Causative Agents
The Immune Response
Detection and Diagnosis
Treatment and Drug Resistance
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 11 : Emerging Bacterial Drug Resistance
Major Concepts
Introduction
History
The Diseases, Causative Agents, and Treatment Options
Mechanisms of Resistance
Diagnosis
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Part 3 : Viral Infections
Chapter 12 : Marburg and Ebola Hemorrhagic Fevers
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 13 : American Hemorrhagic Fevers
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 14 : Lassa Hemorrhagic Fever
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 15 : Dengue Fever and Dengue Hemorrhagic Fever
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 16 : The Human Immunodeficiency Virus and Acquired Immune Deficiency Syndrome
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis and Detection
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 17 : Human Herpesvirus 8 and Kaposi’s Sarcoma
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 18 : Hepatitis C
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 19 : Epidemic and Pandemic Influenza
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 20 : Hantavirus Pulmonary Syndrome
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 21 : Severe Acute Respiratory Syndrome
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 22 : West Nile Disease in the United States
Major Concepts
Introduction
History
The Diseases
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 23 : Monkeypox
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Part 4 : Parasitic Infections
Chapter 24 : Malaria: Reemergence and Recent Successes
Major Concepts
Introduction
History
The Disease
The Causative Agents
The Immune Response
Diagnosis
Treatment and Drug Resistance
Prevention: Failures and Successes
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 25 : Babesiosis
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 26 : Cryptosporidiosis
Major Concepts
Introduction
History
The Disease
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 27 : Chagas’ Disease and Its Emergence in the United States
Major Concepts
Introduction
History
The Disease
The Causative Agent
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Part 5 : Infectious Proteins
Chapter 28 : Creutzfeldt-Jakob Disease and Other Transmissible Spongiform Encephalopathies
Major Concepts
Introduction
History
The Diseases
The Causative Agents
The Immune Response
Diagnosis
Treatment
Prevention
Surveillance
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Part 6 : Special Issues in Infectious Diseases
Chapter 29 : The Emerging Importance of Infectious Diseases in the Immunosuppressed
Major Concepts
Introduction
Immunosuppressed Populations
Selected Causes of Immunosuppression
Infectious Diseases of the Immunosuppressed
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Chapter 30 : The Emerging Threat of Bioweapons
Major Concepts
Introduction
History
Bioterrorism Agents and Diseases
The Threat of Agroterrorism
Preparation for Biological Attacks
Protective Vaccines
Summary
Key Terms
Review Questions
Topics for Further Discussion
Resources
Glossary
Index
Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved.
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Library of Congress Cataloging-in-Publication Data
Beltz, Lisa A., 1960.
Emerging infectious diseases: a guide to diseases, causative agents, and surveillance/Lisa A. Beltz.—1st ed.
p. cm.—(Public health/epidemiology and biostatistics; 10)
Includes bibliographical references and index.
ISBN 978-0-470-39803-6 (pbk.); ISBN 978-1-118-00157-8 (ebk); ISBN 978-1-118-00158-5 (ebk); ISBN 978-1-118-00159-2 (ebk)
1. Emerging infectious diseases. I. Title.
RA643.B45 2011
362.196′9—dc22
2011001414
TABLES AND FIGURES
TablesTable 2.1Immune cells and immune responsesTable 2.2Actions of selected cytokinesTable 3.1Incidence of Lyme disease by stateTable 5.1Human diseases caused by Bartonella speciesTable 5.2Bartonella species that infect humansTable 5.3Treatment for diseases associated with Bartonella infectionTable 6.1Diseases associated with GAS infectionTable 6.2Actions of streptococcal virulence factorsTable 6.3GAS and the human immune responseTable 7.1Diseases associated with E. coli O157:H7 infectionTable 7.2Routes of transmission of E. coli O157:H7Table 7.3E. coli O157:H7 virulence genesTable 8.1Helicobacter species associated with human diseaseTable 8.2H. pylori–induced changes in production of cytokines and chemokinesTable 8.3Agents used in combination for the treatment of H. pylori infectionTable 9.1Diagnostic techniques for Legionnaires’ diseaseTable 9.2Water treatment options to decrease Legionella contaminationTable 11.1Mechanisms of antibiotic drug actionTable 13.1Cytokines active during New World hemorrhagic feversTable 15.1Factors influencing the development of DHF and DSSTable 15.2Roles of immune mediators in dengue infectionTable 15.3Roles of leukocytes in dengue infectionTable 16.1HIV transmissionTable 16.2Total number of AIDS cases in nine U.S. states and Puerto Rico through 2007Table 16.3Viral and immunological characteristics during different stages of HIV infectionTable 16.4Categories of anti-HIV agentsTable 17.1Types of Kaposi’s sarcomaTable 17.2HHV-8 proteins that increase viral growth or survivalTable 19.1Incidence and mortality: Human cases of avian influenza, 2003–January 2008Table 20.1Distinguishing clinical characteristics for HFRS and HPSTable 20.2Pathogenic members of the genus Hantavirus, family BunyaviridaeTable 20.3Hantavirus pulmonary syndrome in the Americas, 1993–2004Table 21.1Summary of probable SARS cases, November 1, 2002–July 31, 2003Table 21.2Graded implementation of community containment measuresTable 22.1West Nile disease in the United States, 2008Table 25.1Tickborne diseases of humansTable 25.2Babesia species and their hostsTable 26.1Several Apicomplexan parasites of humansTable 26.2Immune system components activated by Cryptosporidium infectionTable 28.1Infectious agents of humansTable 28.2Differences between sporadic and variant CJDTable 29.1Some factors that inhibit immune system functioningTable 30.1Categories of potential biological weapons agentsTable 30.2Agents of viral hemorrhagic feverTable 30.3Distribution of the viruses that cause hemorrhagic fever (HF)Table 30.4Agents of viral encephalitis in humansFiguresFigure 1.1Child with smallpoxFigure 1.2Sign announcing smallpox vaccinationFigure 1.3Incidence of diabetes in the United StatesFigure 2.1Yellow fever virusFigure 2.2Transmission via respiratory secretionsFigure 3.1Annual incidence of reported cases of Lyme disease in the United States, by age group and sex, 1992–2004Figure 3.2Reported cases of Lyme disease in the United States, 1994–2008Figure 3.3Erythema migransFigure 3.4SpirocheteFigure 3.5Nymphal Amblyomma americanum (lone star tick) and engorged tickFigure 3.6Approved method of tick removalFigure 4.1Range of one of the principal tick vectors in the United StatesFigure 4.2Lone star tickFigure 4.3Number of ehrlichiosis cases in the United States, 1999–2006Figure 4.4Ehrlichiosis by state, 2001–2002Figure 4.5Black-legged tickFigure 4.6Anaplasmosis cases in the United States, 1999–2006Figure 4.7Anaplasmosis by state, 2001–2002Figure 5.1Small, localized lesion of cat-scratch diseaseFigure 5.2Human body louseFigure 6.1Skin lesions due to impetigoFigure 6.2“Strawberry tongue”Figure 6.3ErysipelasFigure 6.4Group A streptococci growing in chainsFigure 6.5Beta-hemolytic growth: ring of clearing around colonies grown on agar containing sheep red blood cellsFigure 7.1Scanning electron micrograph of E. coli O157:H7Figure 7.2Inoculation of bacteria from a fecal sample onto an agar plate for isolationFigure 8.1Gastric cancerFigure 9.1Bilateral pulmonary infiltrates during Legionnaires’ diseaseFigure 9.2Legionella pneumophila bacilliFigure 9.3Scanning electron micrograph demonstrating the association of Hartmannella vermiformis amoebas with Legionella pneumophila on a potable water biofilm containing Pseudomonas aeruginosa, Klebsiella pneumoniae, and FlavobacteriumFigure 9.4The life cycle of LegionellaFigure 9.5Colony isolation on buffered charcoal-yeast extract (BCYE) agarFigure 9.6Fluorescent antibody staining to detect the presence of L. pneumophilaFigure 10.1Advanced bilateral tuberculosisFigure 10.2Mycobacterium tuberculosisFigure 10.3M. tuberculosis with acid-fast stainFigure 10.4Mobile tuberculosis testing clinic, 1963Figure 10.5Measuring the extent of the hypersensitivity reaction during a Mantoux tuberculin skin testFigure 11.1MRSAFigure 11.2Cutaneous lesion due to MRSA infectionFigure 11.3Electron micrograph of Pseudomonas aeruginosaFigure 11.4Measuring antibiotic resistance: A clearance zone appears around bacteria susceptible to antibiotics on the disksFigure 12.1Surveying for infection during the 1976 Ebola outbreak in ZaireFigure 12.2Graveyard containing some of the first victims of the Ebola outbreak in Sudan in 1976Figure 12.3Lung pathology due to Marburg virus infection, showing breakdown of alveolar walls, leading to pulmonary edemaFigure 12.4Acute tubular necrosis and glomerular fibrin thrombosis in the kidney of a patient with Marburg hemorrhagic feverFigure 12.5Histology of liver tissue infected with Ebola virusFigure 12.6Electron micrographs of Ebola and Marburg virusesFigure 12.7Budding of Ebola virus from the plasma membrane of an infected cellFigure 12.8Sampling animal tissues to determine the reservoir species for Ebola virus, Kikwit, Zaire, 1995Figure 12.9Isolation unit harboring persons with suspected cases of Ebola hemorrhagic fever in 1976Figure 12.10Technician in protective field gear, Zaire, 1976Figure 12.11Barrier clothing donned prior to entering an Ebola isolation ward, Kikwit, Zaire, 1995Figure 12.12Vehicles used to cross the rugged roads of Zaire during the 1976 Ebola outbreakFigure 13.1Petechial lesionsFigure 13.2Cotton ratFigure 13.3“Sandy” appearance of New World arenavirusesFigure 13.4Machupo virusFigure 13.5Working in a Biosafety Level 4 laboratoryFigure 13.6Baiting a rodent trap with peanut butterFigure 14.1Lassa witch doctorsFigure 14.2Serum from a nurse who contracted Lassa fever in Nigeria, 1969Figure 14.3Treating a child with Lassa fever in Sierra LeoneFigure 14.4Hepatitis caused by Lassa virusFigure 14.5Budding of Lassa viruses from an infected host cellFigure 14.6Receiving plasma to maintain blood volume during Lassa feverFigure 14.7Barrier nursing in a men’s Lassa fever ward in Sierra Leone, 1977Figure 14.8Viewing tissue samples during a Lassa fever investigationFigure 15.1Female Aedes aegypti taking a blood mealFigure 15.2Cemetery in New Orleans serving as an urban breeding site for A. aegyptiFigure 15.3Testing water from a tree hole for the presence of mosquito larvaeFigure 16.1Chemical structure of AZT (zidovudine)Figure 16.2Candida infection in the mouth of an HIV-positive personFigure 16.3Toxoplasma infection of the heartFigure 16.4Two human retroviruses that infect T lymphocytesFigure 16.5HIV budding from a T helper lymphocyteFigure 16.6Multinucleated giant cell formed during HIV infectionFigure 16.7Proper disposal of a used needle in a “sharps” containerFigure 17.1Skin lesions of Kaposi’s sarcomaFigure 17.2Kaposi’s sarcoma of the hard palate of an HIV-positive personFigure 17.3Polymerase chain reaction (PCR)Figure 17.4The chemical structure of TaxolFigure 18.1Primary causes of chronic liver diseaseFigure 18.2Cirrhosis of the liverFigure 18.3Lichen planusFigure 18.4Electron micrograph of hepatitis virusesFigure 18.5The chemical structure of ribavirinFigure 18.6Disposing of blood-contaminated materialFigure 19.1Annual mortality rate during recent influenza pandemicsFigure 19.2Boxes of “swine flu” vaccine, stored in connection with the National Influenza Immunization ProgramFigure 19.3H3N2 “Hong Kong flu” virus showing spikes of hemagglutinin and neuraminidase on the surfaceFigure 19.4Inoculating a chick embryo with influenza virus during vaccine preparationFigure 19.5Administration of a live attenuated intranasal H1N1 vaccineFigure 20.1Hantavirus pulmonary syndrome (HPS) cases, by reporting statesFigure 20.2Bilateral pulmonary effusion during HPSFigure 20.3Interstitial pneumonitis and intra-alveolar edemaFigure 20.4Electron micrograph of the Sin Nombre virusFigure 20.5Deer mouse vector of the Sin Nombre virusFigure 20.6Activated immune system: lymph node from an HPS patientFigure 20.7Determining virus numbers in infected cells inside a BioSafety Level 4 laboratoryFigure 20.8Examining samples suspected of involvement in a hantavirus outbreakFigure 20.9Donning protective wear prior to collecting deer mice during a hantavirus field studyFigure 21.1Damage to the alveoli of the lungs caused by SARSFigure 21.2SARS-CoV with projecting spike proteinsFigure 21.3Processing samples from a SARS patientFigure 22.1West Nile cases in the United States, 2000Figure 22.2West Nile cases in the United States, 2003Figure 22.3West Nile cases in the United States through December 15, 2008Figure 22.4Electron micrograph of West Nile virusFigure 22.5Culex tarsalis, the West Nile virus vectorFigure 22.6Application of DEET to clothingFigure 22.7Breeding grounds for Culex mosquitoes: irrigation ditch and water in a tree holeFigure 22.8Capturing wild birds to test for West Nile virus infectionFigure 23.1Humans and nonhuman primates share living space in many countries in Africa and AsiaFigure 23.2Vaccination with vaccinia virus during the smallpox eradication program of the 1970s in West AfricaFigure 23.3Monkeypox skin lesionsFigure 23.4Chickenpox rash on the chestFigure 23.5Electron micrographs of two morphological forms of monkeypox virusFigure 23.6Electron micrographs of other orthopoxviruses that infect humansFigure 23.7Real-time PCRFigure 23.8Dryvax vaccine used to prevent smallpox and monkeypoxFigure 24.1Construction of a drainage ditch to eliminate vector breeding sites, Virginia, 1920sFigure 24.2One of the fruits of malaria reduction programs in the Western Hemisphere: the Panama CanalFigure 24.3Malaria parasite life cycleFigure 24.4Microgametocyte and macrogametocyte: Plasmodium falciparumFigure 24.5Erythrocytes infected by multiple ring-stage Plasmodium falciparumFigure 24.6Plasmodium vivax schizont containing 16 trophozoitesFigure 24.7Chemical structures of quinine and chloroquineFigure 24.8Skin exposure during mixing of the pesticide malathionFigure 24.9Female Anopheles gambiae laying eggsFigure 25.1Babesia protozoa in the tetrad conformationFigure 25.2Babesia ring-form trophozoitesFigure 25.3The chemical structure of clindamycinFigure 26.1Life cycle of CryptosporidiumFigure 26.2Cryptosporidium in the gallbladderFigure 26.3Stool sample containing CryptosporidiumFigure 27.1Romaña’s sign: edema above the right eyeFigure 27.2T. cruzi bloodstream trypomastigote (center)Figure 27.3Cluster of T. cruzi amastigotes inside heart cells (center)Figure 27.4Triatoma infestans, a “kissing bug” vector of Chagas’ diseaseFigure 27.5Life cycle of Trypanosoma cruziFigure 28.1Unsteadiness of a BSE-affected cowFigure 28.2BSE cases in North America, by year and country of death, 1993 and 2003–2010Figure 28.3Areas reporting chronic wasting syndrome in wild deer, elk, and moose, as of March 2010Figure 28.4Normal cellular form of the prion protein versus the scrapie formFigure 29.1Pseudomonas aeruginosaFigure 29.2Clostridium difficileFigure 29.3Shingles due to varicella-zoster virus in a person with a history of leukemiaFigure 29.4Histoplasma capsulatumFigure 29.5Pneumonia resulting from Candida infectionFigure 29.6Coccidioides immitis infection of the skinFigure 29.7Several intracellular Toxoplasma gondii protozoa in the heartFigure 29.8Mild leishmanial lesionFigure 29.9Ascaris lumbricoidesFigure 30.1Skin lesions due to bubonic plagueFigure 30.2Rat flea, the vector of Yersinia pestis, causative agent of bubonic plagueFigure 30.3Hemorrhage of the brain due to anthraxFigure 30.4Skin lesion due to Francisella tularensis infectionFigure 30.5Rash typical of Rocky Mountain spotted feverFigure 30.6Burkholderia, obligate aerobic bacteriaThis book is dedicated to the health care professionals at the front line in the battle against infectious diseases and to the researchers who provide them with information about the enemies and weapons to defeat them.
PREFACE
Headlines and news reports warn of “Flesh-Eating Bacteria,” “Mad Cow Disease,” the AIDS pandemic, and flu pandemics. Drug-resistant bacteria are in our hospitals and our locker-rooms, malaria incidence is on the rise, and TB is reemerging. Every year, new infectious threats appear or old diseases spread to new areas or attack with greater viciousness. Some of the new diseases rear their heads and then suddenly vanish, like SARS, while others may be with humanity for the foreseeable future. The media warn and inform of the newly emerging diseases yet also may capitalize on public fears by overstating the real danger or describing the diseases in the most gruesome terms possible before moving on to the next “killer virus” predicted to kill tens of millions of people. Meanwhile, other, less spectacular diseases spread unnoticed through certain segments of the world’s population (as babesiosis or cryptosporidiosis in immunosuppressed persons or dengue hemorrhagic fever in many parts of the world). This book attempts to provide a balanced overview of some of the emerging and reemerging diseases of current times. No single text could cover all of these diseases, but a number of illnesses have been selected which are found in different regions of the world. Many of these strike tropical regions or developing countries with particular virulence, others are found in temperate or developed areas, and still other microbes and infections are more indiscriminate. In five or ten years, other diseases may have emerged as major killers of humanity while some of the current threats may have been neutralized by the development of new drugs, vaccines, or other preventive measures. Poverty, civil unrest and war, and lack of access to modern health care supplies and facilities have fueled epidemics of some of the diseases covered in this book. If these underlying causes could be nullified or eliminated, many diseases would be controllable and large numbers of people freed from their crippling effects upon health and prosperity.
Since many of the infectious diseases presented in this book are relatively new or little information is known about the causative agent, much of the material has been derived from recent infectious disease journals or other related articles. Other timely information is derived from the Centers for Disease Control and Prevention, the World Health Organization, or MedLine Plus. The excellent Emerging Infections series from the American Society for Microbiology have also provided much of the background material for this book.
This text has been written to accommodate several different groups of students, including but not limited to, upper-level undergraduate or graduate students in biology or medically-related professions, public health students, and persons already working in the healthcare arena. Not all of the information may be useful to every audience but the material (especially some of the immunology and microbiology) is presented for use by those who wish to have a greater understanding of how the microbes function and cause disease and how the human body attempts to remove or minimize the damage. This information may be skipped without losing understanding of the disease itself or its prevention and treatment.
The diseases are divided by type of causative agent: bacteria, viruses, protozoa, or infectious protein. Those chapters which deal with diseases induced by infection with a single organism or group of organisms are organized in a similar fashion: introduction, history, the disease(s), the causative agent(s), the immune response, diagnosis, treatment, prevention, and surveillance. The Major Concepts section presents a brief overview of the most important concepts found in the chapter. The Summary is a thumbnail sketch of the basic information about the microbe and the associated disease. Review Questions help students to test their knowledge of the material, while Topics for Further Discussion allow for a wider conversation of the implications of the disease and challenge students to “think outside of the box” to develop new solutions. There are no right answers or solutions to the material found within this section; rather, it is hoped that any students entering into the medical or research fields, as well as those destined to serve in public health, may learn to search for innovative ways of dealing with health-related problems.
The two introductory chapters provide basic information that will be useful for the other chapters, including an introduction to emerging and reemerging infectious diseases, proposed causes for disease emergence, very basic microbiology, and very basic immunology. The latter is included since a discussion of disease needs to include how the host attempts to defend itself as well as what can go wrong with this “protective” response. The last two chapters cover topics of particular interest. Chapter Twenty-Nine discusses emerging diseases in immunocompromised individuals since the numbers of people in this group are increasing rapidly, posing unique challenges to public health. Chapter Thirty describes several of the agents that may be used in acts of bioterrorism. Many of these agents have already been used for this purpose. Hopefully, the spread of knowledge about the threat of bioterrorism will discourage its usage in the future.
Lisa A. Beltz
New Philadelphia, Ohio
February 2011
THE AUTHOR
Dr. Lisa A. Beltz is an assistant professor in the Department of Biology at Kent State University at Tuscarawas, in New Philadelphia, Ohio. She has taught a number of medically-related biology courses during her 14 years of teaching at Kent State University and the University of Northern Iowa. Prior to teaching, she studied two of the diseases described in this book. While a graduate student at Michigan State University, she examined the mechanisms by which Trypanosoma cruzi inhibits human immune responses, allowing the parasite to kill large numbers of people in Central and South America. Later, at Johns Hopkins University and the University of Pittsburgh, she studied interactions between the simian and human immunodeficiency viruses and bone marrow cells as well as exploring the mechanisms by which HIV kills white blood cells. Dr. Beltz was the co-originator of the course Cancer and Emerging Infectious Diseases during her time in Iowa. The need for a college-level textbook in this field became apparent over her seven years of teaching the course. Dr. Beltz’s more recent research has involved studying the impact of nitrate and other environmental contaminants on the human immune system and studying the effects of green tea components upon normal and cancerous white blood cells.
ACKNOWLEDGMENTS
I would like to thank the following reviewers for their time and many helpful suggestions: Gokul Das, John E. Gustafson, Kathy Hanley, Carrie Horwich, Frank Jenkins, Stanley Katz, and Terri Rebmann. Mr. Andrew Pasternak and Seth Schwartz of Jossey-Bass played major roles in the writing of this text. Their ideas shaped the book and guided every step of its creation. I am also grateful for the support of the faculty and administration of Kent State University at Tuscarawas and Kent State University at Kent, particularly Dean Gregg Andrews from the Tuscarawas Campus, Dr. James Blank, Chair of the Department of Biology, Dr. Christopher Fenk, and Dr. Donald Gerbig. They provided me with the time and atmosphere in which to develop my ideas into the final product. Finally, I wish to thank my family for their patience and encouragement during the writing process.
—L.A.B.
PART I
INTRODUCTION TO EMERGING INFECTIOUS DISEASES
CHAPTER 1
INFECTIOUS DISEASES PAST AND PRESENT
LEARNING OBJECTIVES
Discuss the roles of plague and smallpox in human historyDiscuss the most important infectious diseases in the world todayDiscuss the linkages between infectious diseases, poverty, and civil unrestDescribe a number of emerging and reemerging infectious diseases found in the Americas, outside of the Americas, and throughout the worldDiscuss a number of factors contributing to the emergence or reemergence of infectious diseasesGain a sense of the number of new infectious diseases that have emerged recently and the rapid pace of discovery of the microbes responsible, development of antimicrobial drugs, and evolution of microbial drug resistanceMajor Concepts
History
Infectious diseases have had a great impact on human history, killing vast numbers of persons and disabling or disfiguring many others. Some diseases have transformed the social and economic landscape of a region, as when the decline in the peasant population following the Black Death contributed to the end of the feudal system. The fight against smallpox led to the development of vaccination, a weapon in the human arsenal that prevented major loss of life by protecting people from a wide range of diseases. Due to an ever-better understanding of the causative agents of infectious diseases, other tools have been developed to prevent or treat illnesses, including improved sanitation, greater availability of clean drinking water, the increased use of disinfectants, the discovery of antimicrobial compounds, and improvements in the inspection, processing, and preparation of food and drink. The incidence and severity of infectious diseases have fallen in developed nations but are again on the rise worldwide.
Infectious Diseases Today
The leading causes of death due to infectious diseases in the world today are lower respiratory tract infections, diarrheal diseases, HIV/AIDS, tuberculosis, malaria, and dengue hemorrhagic fever and shock syndrome. Many of the victims of these diseases belong to the most vulnerable segments of our population, the very young and the very old, those weakened by other pathological conditions, and those with compromised immune responses. Many other diseases affect smaller segments of humankind. Some of these preferentially strike those living in certain climates or ecosystems, in lower socioeconomic groups, or in regions of civil unrest and war. Other diseases are more prevalent in some racial groups, age ranges, occupations, or one gender. Still other diseases are indiscriminate killers. Incidence of some diseases peaks in certain seasons, while others occur year round.
Emerging and Reemerging Infectious Diseases
Many diseases have either been described for the first time within the past 40 to 50 years or have increased in incidence, severity, or geographical range. This text focuses on a number of such diseases and the associated microbes. Several factors in combination have contributed to the explosion of emerging and reemerging infectious diseases in recent times (as evidenced by the Timeline at the end of this chapter). Our awareness of new infections may be due in part to improved detection and understanding of the underlying causes of illness. Many of the emerging diseases, however, appear to be entirely new to humans, while many reemerging diseases represent increasing threats to humankind. Several of the factors believed to contribute to the emergence or reemergence of infectious diseases include microbial evolution, the trend toward increasing urbanization, population migrations between regions or into formerly uninhabited areas, the ease and speed of long-distance movement of persons and materials, natural disasters, climatic and ecological changes, and decreased vaccination rates in many regions of the world. One of the important factors contributing to the rapid emergence of new infections is the increasingly large numbers of immunocompromised individuals who are vulnerable to the development of severe or life-threatening diseases as a result of infection by organisms formerly viewed as nonpathogenic.
History of Infectious Diseases
Much of the history of humankind has been critically shaped by infectious diseases. Large, widespread outbreaks of bubonic, pneumonic, and septicemic plague, caused by infection with Yersinia pestis, have struck repeatedly, including the Plague of Justinian from 542 to 767, which killed 40 million people in Europe and Asia Minor and initiated the Dark Ages, and the Black Death, lasting from the fourteenth to eighteenth centuries. The latter began in Central Asia and subsequently spread to China, India, and Asia Minor, entering Italy in 1347. Twenty-five to fifty percent of the population of Europe succumbed to the plague within the next three years, leading to the death of many peasants and the abandonment of much of the agricultural land. The resulting food shortage and loss of an abundant workforce rendered the existing governments ineffective. These were major factors in the eventual collapse of the feudal system and the rise of middle-class artisans. Improvements in sanitation were also implemented due to lessons learned during the plague years.
Smallpox is another disease that changed the face of human history, quite literally, for over three thousand years, afflicting humans with horrific and disfiguring scars, blindness, and death for most of our known existence. Its eradication has been one of our greatest achievements.
The rich and powerful were not spared the attention of this deadly pestilence. Scars were even found on the mummy of the Egyptian pharaoh Ramses V. Throughout the ages, the fatality rate often approached 30%, with 65% to 80% of the survivors left with pockmarks on their faces as reminders of their ordeal. As late as the 1700s, 10% to 14% of the children in France, Sweden, and Russia died of smallpox. Surviving the disease was almost a rite of passage, and no parent could be totally at ease until his or her children had vanquished that most dreaded foe.
FIGURE 1.1 Child with smallpox
Source: CDC/Jean Roy.
“The smallpox was always present,” wrote T. B. Macaulay, “filling the churchyards with corpses, tormenting with constant fears all whom it had stricken, leaving on those whose lives it spared the hideous traces of its power, turning the babe into a changeling at which the mother shuddered, and making the eyes and cheeks of the betrothed maiden objects of horror to the lover.”
It was observed in China over a thousand years ago that survivors of smallpox did not contract the disease again, even after extended exposure to infected persons. It was additionally discovered that inoculation of previously unexposed persons with material from dried smallpox scabs derived from persons with mild cases of the disease often safeguarded the inoculated persons against developing severe infection at a later time. This practice was known as variolation and occasionally resulted in death. Variolation was brought to Europe in 1721 by Lady Mary Wortley Montagu, the wife of the British ambassador to Turkey. Decades later, Edward Jenner acted on the common observation that milkmaids, who typically developed the mild disease cowpox, did not later suffer from smallpox or develop the hideous scars present on most members of society. In 1796, he modified the practice of variolation by inoculating a young boy, James Phipps, with material from cowpox scabs and subsequently challenging him with smallpox. Fortunately for James (and humanity), the boy was protected.
Thus began the age of vaccination, which ultimately led to the eradication of smallpox as a result of the concerted efforts of many dedicated individuals working under difficult conditions throughout the world for a decade. The program featured the quarantine of patients and their contacts as well as vaccination of all potential contacts. Ali Maalin from Somalia is believed to have acquired the last naturally occurring case of smallpox in 1977. Several subsequent cases occurred several years later in England following viral escape from a laboratory.
FIGURE 1.2 Sign announcing smallpox vaccination
Source: CDC.
While smallpox remains the only disease that humans have totally eliminated from nature, the lessons learned during this triumph of humans over one of its most deadly foes have been applied many times in subsequent years. Highly effective vaccines have been developed and brought into widespread use to tame other serious microbial diseases such as polio, whooping cough, German measles, mumps, and tetanus. The science of epidemiology, initiated by John Snow to trace the source of a cholera epidemic in London in the 1850s to a specific water pump, transformed public health. The “germ theory of disease,” developed by Louis Pasteur, Robert Koch, John Lister, and others in the 1860s, revolutionized beliefs concerning the origins of diseases. These developments—along with improvements in sanitation, the availability of clean drinking water, practices such as pasteurization and sterilization of beverages and food, increased use of disinfectants, the discovery of antimicrobial compounds such as antibiotics (discussed in Chapter Eleven) and antiviral drugs, improvement in the inspection of meat and processing facilities, more thorough cooking of meat and eggs, and educational programs—eventually served as tipping points for many infectious diseases in the developed areas of the world. The numbers of cases of microbial illnesses dramatically declined: the incidence of tuberculosis, malaria, cholera, and many other diseases fell either regionally or around the world. Many persons in the public health arena in the early 1970s declared an imminent end to threats by infectious diseases.
The victory dance proved premature. A number of factors reversed the gains made in humankind’s war against pathogenic microbes. Diseases thought to be on the brink of extinction reemerged with a vengeance, and many new devastating diseases, including AIDS and a variety of hemorrhagic fevers, began to appear at an alarming rate. Rather than an end to the war against microbes, we were surprised to find ourselves facing fresh troops and new enemies. The battle continues as both sides reassess their strategies and struggle to develop new weapons better suited to the continuingly evolving situation.
The Role of Infectious Diseases in the World Today
A number of serious infectious diseases affect humans currently. The type of microbe, the mode of transmission, and the incidence of disease within a population or region varies according to income levels and socioeconomic status, age, gender, type of employment, general health parameters, social customs, housing preferences, climate and ecology of the region (temperature and rainfall; woodland versus prairie versus coastline), and the types and abundance of vector and reservoir species. Many of the diseases strike primarily members of the population with poor immune responses: the very young, the elderly, pregnant women, and immunocompromised individuals. Some infectious diseases, including Lyme disease and hantavirus pulmonary syndrome, preferentially strike men and women between the ages of 20 and 40. Other serious illnesses, such as pandemic influenza, are more indiscriminate with regard to their victims’ age. Due to differences in occupational exposure and recreational activity, some infectious diseases, among them the American hemorrhagic fevers and ehrlichiosis, strike men more frequently than women because males are more likely to spend time working in the cornfields and on cattle ranges or hunting and fishing in the wooded areas where the rodent or insect vectors of these diseases are found. Others are more common among women. One such example is the prion disease kuru, which afflicted women exposed to prions while preparing brains for consumption during funeral rites. Persons in poor overall health are more likely to succumb to infectious diseases. Once infected with one microorganism, individuals are more susceptible to other infections due to generalized immunosuppression. Social customs may increase infectious disease incidence as exemplified by funeral rites that exposed women to the Ebola virus. The type of housing common to a given region also affects disease incidence. People living in homes with thatched roofs and no screened windows or doors are exposed to disease vectors, as seen with Chagas’ disease in South America, where the “kissing bug” vector bites humans sleeping in the thatched huts at night. Tropical areas are home to many, but not all, of the emerging infections presented in this book. A hot, humid environment may support large populations of insect vectors year round. Some microbes are unable to survive in colder environments. Vector and reservoir species availability also influences the spread of diseases. Chagas’ disease is moving into parts of the southern United States, where the insect vector can survive the winters and where abundant small mammals are present to serve as reservoir hosts.
The population of immunosuppressed individuals in both developed and developing regions is increasing, leading to the emergence or reemergence of many infectious diseases. The AIDS pandemic has been responsible for much of this increase, especially in developing regions. Organisms other than HIV, such as Epstein-Barr virus (causative agent of mononucleosis) and herpesviruses, suppress immune reactivity. The aging of the population in developed regions is also a factor because various immune system components either decrease in mass (thymus), numbers (some populations of T lymphocytes), or effectiveness (T and B lymphocytes, natural killer cells) as persons age. Diabetes and cancer chemotherapy also compromise immune response. The incidence of both diabetes and cancer is increasing in developed nations due to obesity and recent alterations in diet, exercise, lifestyle, and occupation.
Depression also adversely affects various aspects of the immune response because functions of the central nervous system and the immune system are closely linked. Anti-inflammatory medications that are used to treat autoimmune disorders, such as rheumatoid arthritis, Crohn’s disease, psoriasis, and systemic lupus erythematosus (such as corticosteroids), suppress lymphocyte responses and increase susceptibility to infectious diseases, such as tuberculosis and staphylococcal infections.
FIGURE 1.3 Incidence of diabetes in the United States
Several infectious diseases cause a great degree of suffering and death in the world today. Lower respiratory tract infections are caused by several bacteria, viruses, and protozoa, including Streptococcus pneumoniae,Haemophilus influenza, respiratory syncytia virus, influenza viruses, parainfluenza viruses, and Pneumocysitis jiroveci (formerly P. carinii). These together constitute the leading cause of death due to infectious disease. Diarrheal diseases are the second leading infectious cause of death throughout the world and are the primary cause of malnutrition. Diarrheal organisms include Vibrio cholerae,Shigella spp., Campylobacter spp., Salmonella spp., rotavirus, Cryptosporidium spp., E. coli, and Giardia lamblia. Children under the age of 2 years are most vulnerable to these infections, and 1.5 million children die annually of diarrheal disease. HIV/AIDS is the single leading infectious cause of death. In 2007, some 33 million persons were living with HIV, and 2.7 million new infections were recorded. Approximately 2 million HIV-related deaths occur each year, and 25 million persons have died from AIDS since the mid-1980s. The tuberculosis bacterium infects about one-third of the world’s population and killed almost 1.6 million people in 2007. Many people are coinfected with HIV and M. tuberculosis: indeed, tuberculosis is one of the leading causes of death in HIV-positive persons. Malaria caused around 1 million deaths in 2005, and 247 million persons were infected with the parasite responsible. Very young African children are especially vulnerable to infection and death and average 1.6 to 5.4 episodes of malarial fever per year. We are currently in the midst of a pandemic caused by the dengue virus, resulting in the extremely painful dengue fever (“breakbone fever”) or the very dangerous dengue hemorrhagic fever, which has a high fatality rate if untreated. Fifty-six million infections occur each year, and the number of cases and disease range are increasing, with explosive outbreaks being reported.
The Links Between Infectious Diseases, Poverty, and Civil Unrest
Infectious diseases continue to be major causes of human death in the world. This is particularly true for areas that are gripped by poverty and the associated ills of decreased access to clean drinking water, malnutrition, overcrowding, substandard housing that does not fully protect against physical or biological threats (temperature extremes, wetness or dryness, insects, and rodents), inadequate health care, and poor educational opportunities. These factors combine to undermine the health of infants, children, and adults in the affected regions, leaving them vulnerable to infectious illnesses. Exposure to insect and rodent vectors in the home increases the spread of pathogenic microbes responsible for diseases such as bubonic plague, malaria, yellow fever, and Lassa fever. Contaminated water supplies transmit diseases such as cholera and schistosomiasis. Overcrowded living conditions, such those found in the slums of major urban centers, homeless shelters, and some prisons, nursing homes, and mental health facilities, permit the rapid spread of infections such as tuberculosis and typhus. Women may be forced into prostitution to obtain money for food for themselves and their children, increasing their risk of acquiring sexually transmitted diseases such as AIDS and syphilis. Children born of infected mothers may become infected in utero, during labor, or via contaminated breast milk. Persons addicted to drugs or alcohol may live in poverty or turn to prostitution in order to obtain funds to feed their habit.
Once individuals in a poverty-stricken region have acquired an infectious disease, they are unlikely to receive adequate treatment due to the inability to pay for services and medications or the lack of health care facilities and practitioners in close proximity to their residence. Many impoverished regions are located in remote areas with few roads. Most of the population may not own a motor vehicle to allow travel to distant sites, and fuel may be either too expensive or too scarce to permit its use by the majority of persons. Roads may be in poor condition or impassable during the wet season. Many governments may be unable or unwilling to provide basic health services or emergency care. Educational programs that could reduce disease incidence or severity are often of limited value because much of the population may not own televisions or radios and may not read newspapers due to illiteracy.
Poverty and disease often form a vicious circle that entraps large regions of the world today. As noted, poverty may set the stage for sickness. Sickness may then deepen the poverty of an area as individuals who could have been vital members of the workforce, producing food and bringing money into the region, are too ill to be fully productive or to work at all. Corporations may be unwilling to bring factories into regions with ill workers. Areas of sub-Saharan Africa suffer from decreased tourism as travelers hesitate to expose themselves to tropical diseases, some of which are difficult to prevent or treat. Ill children may have frequent absences from school. Some infectious diseases impede children’s physical and cognitive development, interfering with their ability to learn the information and skills necessary to lead themselves and their societies out of the grip of poverty and increasing the distance between developed and developing regions of the world.
Many regions of the world suffer under the twin burdens of poverty and civil unrest. Civil wars as well as wars between nations force mass population movements. Combatants and refugees carry diseases from an indigenous region to other areas. Agricultural activity and economic development are challenged. Refugee camps may be hotbeds of infectious disease due to overcrowding, inadequate clean water supplies, lack of proper sanitation facilities, and malnutrition. Areas of active combat are barriers to transportation of food, medicine, and vaccines, not only to the involved area but also to areas served by the associated roads or waterways. Civil unrest and wars disrupt the fabric of society and may tear apart the social mores of the culture. This may further the spread of disease as sexual practices change in manners conducive to microbial transmission.
The role of infectious disease in the world today is linked to a region’s income level. In the world as a whole, coronary heart disease and stroke and cerebrovascular disease were the leading causes of death, responsible for 12.2% and 9.7% of the deaths, respectively, in 2004, according to the World Health Organization. Four of the remaining ten leading causes of death in the world are due to infectious diseases (lower respiratory tract infections, 7.1%; diarrheal diseases, 3.7%; HIV/AIDS, 3.5%; and tuberculosis, 2.5%; total, 16.8%). Among low-income countries, six of the ten leading causes of death were infectious diseases (lower respiratory tract infections, 11.2%; diarrheal diseases, 6.9%; HIV/AIDS, 5.7%; tuberculosis, 3.5%; neonatal infections, 3.4%; and malaria, 3.3%; total, 34.0%). In middle-income countries, on the other hand, two of the ten major causes of death were of an infectious nature (lower respiratory tract infections, 3.8%, and tuberculosis, 2.2%). Among high-income countries, only one of the ten leading causes of death in 2004 was an infectious disease (lower respiratory tract infections, 3.8%). Less than 25% of the people in low income countries live to the age of 70 years, and more than one-third of the deaths are among individuals under the age of 14 years. In middle-income countries, almost 50% of the population dies after the age of 70, and that figure exceeds 67% in high-income countries. The proportion of deaths among those under the age of 14 years is 10% and 1% in middle- and high-income countries, respectively.
Emerging and Reemerging Infectious Diseases
No one textbook can cover the vast numbers of emerging and reemerging infectious diseases that have either been discovered during the past four to five decades or have greatly increased in incidence or virulence regionally or worldwide during that time. A number of these have been selected for inclusion in this book. These include viral, bacterial, and protozoan infections and a number of important diseases found in both tropical and temperate and both developed and developing regions of the world. Some of these are familiar to the general public, while others are virtually unknown even to most members of the medical community in the developed world. The sheer number of new infectious organisms and their spread to novel geographical regions complicates the tasks of physicians, nurses, public health agencies, epidemiologists, and legislators in their roles of safeguarding the general population against infection. This text attempts to draw attention to a subset of these diseases, some of which were once as obscure and remote as slim disease in Africa was to health care personnel before the recognition of the AIDS pandemic. The health and lives of billions of people in the future relies on vigilance of health workers to trends in old diseases and to the emergence of others.
The following diseases are presented in this book:
Diseases Found Primarily in the Americas
Lyme disease: multisymptom disease transmitted by tick bite; includes rash, arthritis, neurological manifestationsEhrlichiosis: potentially serious or fatal bacterial infection of white blood cells; transmitted by tick biteHantavirus pulmonary syndrome: severe to fatal respiratory disease found most commonly in the American Southwest; deer mice serve as disease reservoirsWest Nile encephalitis in the United States: results in rare but serious neurological disease; transmitted by mosquito biteAmerican hemorrhagic fevers: hemorrhagic fevers with high fatality rates found in South and North America; rodents serve as reservoir speciesChagas’ disease in the United States: potentially fatal parasitic infection of the blood that leads to cardiac failure; transmitted by “kissing bugs”Diseases That Occur Primarily Elsewhere in the World
Marburg and Ebola hemorrhagic fevers: hemorrhagic fevers with high fatality rates found primarily in AfricaLassa fever: a hemorrhagic fever found primarily in western Africa; transmitted by inhalation of contaminated rodent excretaMonkeypox: a potentially fatal smallpoxlike disease found primarily in Central Africa; transmitted directly between humansMalaria (reemergent and newly drug-resistant): potentially fatal parasitic infection of red blood cells; transmitted by mosquito bitesVariant Creutzfeldt-Jakob disease and other transmissible spongiform encephalopathies: fatal neurological diseases caused by an infectious protein; transmitted between humans or by consumption of infected beefDiseases That Occur Around the World
Drug-resistant bacteria: includes methicillin- and vancomycin-resistant bacteria as well as drug-resistant strains of Pseudomonas aeruginosa and Streptococcus pneumoniaeGroup A streptococci: cause potentially fatal infections such as scarlet fever, necrotizing fasciitis, childbed fever, and toxic shock syndromeLegionnaires’ disease: a potentially fatal respiratory infection; transmitted by inhalation of bacteria in aerosolized water dropletsDengue fever: an extremely painful disease that may progress to the often fatal dengue hemorrhagic fever or dengue shock syndromeEscherichia coli O157:H7: causes potentially fatal diseases such as hemolytic uremic syndrome and hemorrhagic colitis; transmitted by the oral-fecal routeHelicobacter pylori: causes peptic ulcers and hepatocellular carcinomaBartonella species: cause several potentially serious diseases including cat-scratch fever, trench fever, and bacillary angiomatosisHIV/AIDS: fatal immunosuppressive disease; transmitted through sexual contact or bloodKaposi’s sarcoma: cancer caused by human herpesvirus-8 that can be fatal to HIV-positive personsHepatitis C: potentially fatal liver disease caused by a bloodborne virusSevere acute respiratory syndrome (SARS): potentially fatal respiratory illness; transmitted via inhalationInfluenza: pandemic influenza strains result in widespread loss of life; transmitted via inhalationTuberculosis: reemergent lung disease that has become resistant to many commonly used drugs; transmitted by inhalationCryptosporidium: causes severe diarrheal disease with a high fatality rate in immunosuppressed persons; transmitted via contaminated water or foodBabesiosis: potentially fatal parasitic infection of red blood cells; transmitted by tick biteOther chapters discuss diseases that particularly imperil persons with suppressed immunity (a rapidly growing segment of human societies) and the emerging threat of biological warfare agents.
In addition to the diseases covered in this book, many others are being studied by researchers around the world. For example, in the journal Emerging Infectious Diseases, published by the Centers for Disease Control and Prevention, the following microbes or diseases were discussed in the September 2009 issue: avian bornaviruses, Baylisascaris, bluetongue virus, bocavirus, Campylobacter enteritis, Candida dubliniensis,Chlamydia, feline infectious peritonitis virus, foot-and-mouth disease, Gordonia sputa, hantavirus, Kyasnur Forest disease virus, Merkel cell polyomavirus, rhinovirus C, rotavirus, Saffold cardiovirus, strongyloidiasis, Zika virus, and zygomycosis. The following were covered in the October 2009 issue: acute Q fever, Aichi virus, anthrax, Borrelia hispanica relapsing fever, coxsackievirus, human bocavirus 2, Japanese encephalitis virus, leishmaniasis, lymphocytic choriomeningitis virus, melioidosis, nontuberculosis mycoplasma infection, novel arenavirus in southern Africa, plague, Pneumonocystis jirovecii, rabies, rickettsia, Salmonella enterica, and scrub typhus.
Factors Contributing to the Emergence of New Infectious Diseases and the Spread and Evolution of Older Diseases
A number of factors have led to the recent increase in the emergence and reemergence of infectious diseases. One trivial factor may be increased awareness of a disease or the discovery of an infectious cause for an old affliction. An example of the latter is our relatively recent awareness of the bacterium H. pylori as the cause of peptic ulcers and hepatocellular carcinoma. In many cases, however, older diseases have either undergone increases in incidence or virulence regionally or throughout the world or novel diseases have appeared in the human population. Some of these changes result from microbial evolution through mutation of their DNA or RNA or by the acquisition of new genetic material in the form of plasmids or via transformation or transduction by a bacteriophage. Some microbes, such as influenza and HIV, have rapid mutation rates: influenza viruses of pigs, birds, and humans may exchange RNA if they happen to infect the same cell, and HIV uses an error-prone enzyme during replication and lacks a repair mechanism. The pathogenic E. coli O157:H7 contains several virulence factors that are borne on either a plasmid or a bacteriophage that has infected the bacterium. These changes in genetic material allow the development of drug-resistant microbes, followed by natural selection processes that are fueled by factors such as medicinal overuse of drugs, agricultural practices, patient noncompliance with correct drug dosage, and failure to complete the course of treatment.
Several additional factors involve the movements of individuals or groups. One such factor is the trend toward increasing urbanization, which has moved drawn numbers of people away from their lives in traditional villages to large population centers with different social customs and moral values concerning sexual practices. The rapid increase in city size has not allowed the time and resources necessary for careful planning, resulting in haphazard growth and the appearance of huge slum areas with overcrowded, shoddy housing and very limited access to sanitary waste disposal facilities and clean water for drinking, cooking, bathing, and laundering clothing.
Another factor, noted earlier, is the mass migration of populations (civilians or military personnel) that occurs during war or civil unrest and the resulting spread of disease to new areas, especially under conditions that also allow movement of disease vectors or reservoir species. Such population movements occurred during the exploration and colonization of the Americas and the importation of slaves followed by the introduction of European and African diseases into New World groups, often with disastrous results for the indigenous peoples. During the Pacific campaign of World War II, North American and European soldiers serving in Asia were heavily afflicted by tropical maladies such as malaria, dysentery, and typhoid fever.
A third factor is the rapid movement of individuals and materials by modern transportation systems. A person may travel around the world by air in several days, carrying pathogenic microbes to a wide range of new hosts. A recent outbreak of mumps was linked to an infected individual flying into and out of a number of American cities within the span of a week. SARS traveled from China to Toronto’s Chinatown in a similar manner in 2003. Infected vector species may also bring diseases into new areas, as occurred with the arrival of West Nile virus via its mosquito vector on a ship that arrived in New York Harbor in the summer of 1999. Reservoir hosts may also travel illicitly aboard ships, as the rats bearing bubonic plague from Asia to California did in the 1800s. Other infected reservoir hosts may be imported as pets (monkeypox-infected African rodents were brought into the United States in 2003) or for medical research purposes (Marburg hemorrhagic fever broke out in Germany and Yugoslavia in 1967 in primate centers housing African green monkeys).
A fourth factor is the settlement and clearing of “virgin” territory for farming in the rain forests of South America, Asia, and Africa. This brought humans into greater contact with new species of animals and disrupted existing ecosystems, allowing the emergence of diseases such as Argentine hemorrhagic fever due to shifts in rodent populations inhabiting the newly developed cornfields in the Pampas and the emergence of HIV in humans, believed by many to have entered people when a macaque infected with the simian immunodeficiency virus bit a farmer trying to carve out a living in the rain forests of sub-Saharan Africa.
Natural disasters and climatic factors play roles in disease emergence. A natural disaster triggered a large outbreak of bubonic and pneumonic plague in India in 1994 after a long disease-free period. It was believed to have been initiated by changes resulting from a large earthquake and its aftershocks, followed by mass population movements and rapid expansion of a population of rats that were particularly suited to host and transmit Yersinia pestis to humans.
Climatic factors contributed to the recent appearance of a new respiratory disease in the United States. The mild winter and wet spring accompanying El Niño in the southeastern United States in 1993 led to an unusual abundance of pinyon nuts in the Four Corners region of Arizona, New Mexico, Colorado, and Utah. The deer mouse population of that region exploded, leading to crowding among the mice and their increased contact with the Navaho residents of the area. Some members of the mouse population were infected with Sin Nombre virus, which subsequently spread to numerous other mice and then to humans, leading to the first reported outbreak of the often fatal hantavirus pulmonary syndrome. Navaho folklore had previously warned of death stalking the people following a mild winter with many pinyon nuts.
