Infectious Diseases: In Context – Finals/ 9/25/2007 11:15 Page 17
Introduction
Humanity shares a common ancestry with all living things on Earth. We often share
especially close intimacies with the microbial world. In fact, only a small percentage of the
cells in the human body are human at all. ‘‘We’’ are vastly outnumbered, even within our
bodies, by microbial life that can only be counted on the same scale as the vast numbers of
stars in the universe. This is also an essential relationship, because humanity could not
survive without an array of microflora that both nourish us and that provide needed
enzymes for life processes.
Yet, the common biology and biochemistry that unites us also makes us susceptible
to contracting and transmitting infectious disease.
Throughout history, microorganisms have spread deadly diseases and caused widespread epidemics that have threatened and altered human civilization. In the modern era,
civic sanitation, water purification, immunization, and antibiotics have dramatically reduced
the overall morbidity and the mortality rates of infectious disease in more developed
nations. Yet, much of the world is still ravaged by disease and epidemics; new threats
constantly appear to challenge the most advanced medical and public health systems.
Although specific diseases may be statistically associated with particular regions or
other demographics, disease does not recognize social class or political boundary. In our
intimately connected global village, an outbreak of disease in a remote area may quickly
transform into a global threat. Given the opportunity, the agents of disease may spread
across the globe at the speed of modern travel, and also leap from animals to humans.
The articles presented in these volumes, written by some of the world’s leading
experts, are designed to be readable and to instruct, challenge, and excite a range of
student and reader interests while, at the same time, providing a solid foundation and
reference for more advanced students and readers. It speaks both to the seriousness of
their dedication to combating infectious disease and to the authors’ great credit that the
interests of younger students and lay readers were put forefront in preparation of these
entries.
The editors are especially pleased to have contributions and original primary source
essays within the volumes by experts that are currently in the forefront of international
infectious disease research and policy. Jack Woodall, Ph.D., recounts memories of
belonging to a team that identified and determined the cause of Machupo hemorrhagic
fever in ‘‘Virus Hunters’’ and of his association with the developer of the yellow fever
vaccine in ‘‘Yellow Fever.’’ He also explains ‘‘ProMED,’’ a disease-reporting system (of
which Woodall is a founder) that allows scientists around the world, whether in the
hospital, laboratory, or the field, to share real-time information about outbreaks of
emerging infectious diseases. Jack Woodall now serves as the director of the Nucleus
for the Investigation of Emerging Infectious Diseases at the Federal University of Rio de
Janeiro in Brazil.
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Introduction
Stephen A. Berger, M.D., Ph.D., Director of Geographic Medicine at Tel Aviv
Medical Center in Tel Aviv, Israel, served as a contributing advisor for Infectious Diseases:
In Context and was the developer of GIDEON (Global Infectious Disease and Epidemiology Network), the world’s premier global infectious diseases database. Dr. Berger
explains the Web-based tool that helps physicians worldwide diagnose infectious diseases.
Dr. Berger also contributes ‘‘Travel and Infectious Disease’’ and a special introduction.
Dr. Berger’s contributions reflect a dedication to teaching that has five times earned him
the New York Medical College Teaching Award. Dr. Berger, author of numerous articles
and books, including Introduction to Infectious Diseases, The Healthy Tourist, and Exotic
Viral Diseases: A Global Guide, was gracious with his time, writing, and advice.
The editors are indebted to both of these distinguished scientists for their generous
contributions of time and compelling material.
Readers interests were are also well-served by Anthony S. Fauci, M.D., Director of the
National Institutes of Allergy and Infectious Diseases, for what was, at the time Infectious
Diseases: In Context went to press, a preview of his latest version of the map of emerging
and re-emerging infectious diseases, and also by L. Scott Clements, M.D., Ph.D., for his
advice and articles, including ‘‘Childhood Infectious Diseases: Immunization Impacts.’’
Space limitations of this volume force the editors to include only those infectious
diseases that directly affect human health. It is important to note, however, that diseases
affecting plants and animals can have a significant indirect impact on the lives of humans.
The 2001 outbreak of foot and mouth disease in the United Kingdom, for example,
resulted in the slaughter of over six million pigs, sheep, and cattle, crippling farmers,
tourism, and other commerce, and ultimately costing an estimated four billion dollars to
the U.K. economy. At press time, the cocoa industry in Ghana is threatened by the Cocoa
Swollen Shoot Virus, where farmers are reluctant to cut down their infected mature cocoa
trees and plant healthy seedlings. Ghana is among the leading exporters worldwide of
cocoa for chocolate. Scientists are also concerned about a lack of forthcoming information
from the Chinese government concerning an epidemic virus among pigs in China that is
contributing to a pork shortage and the strongest inflation in China in a decade.
Although these diseases cannot inflict illness in humans, they can ultimately affect the
nutritional, social, economic, and political status of a nation and its people.
Despite the profound and fundamental advances in science and medicine during the
last fifty years, there has never been a greater need for a book that explains the wideranging impacts of infectious disease. It is hubris to assume that science alone will
conquer infectious diseases. Globally, deaths due to malaria alone may double over the
next twenty years and ominous social and political implications cannot be ignored when
death continues to cast a longer shadow over the poorest nations.
The fight against infectious disease depends on far more than advances in science and
public health. The hope that threats and devastation of infectious diseases could be
eliminated for all humankind have long since been dashed upon the hard realities that
health care is disproportionately available, and cavernous gaps still exist between health
care in wealthier nations as opposed to poorer nations. Victory in the ‘‘war’’ against
infectious disease will require advances in science and advances in our understanding of
our fragile environment and common humanity.
K. Lee Lerner & Brenda Wilmoth Lerner, editors
DUBLIN, IRELAND, JULY
2007
Brenda Wilmoth Lerner and K. Lee Lerner were members of the International Society for
Infectious Disease and delegates to the 12th International Congress on Infectious Disease
in Lisbon, Portugal, in June 2006. Primarily based in London and Paris, the Lerner &
Lerner portfolio includes more than two dozen books and films that focus on science and
science-related issues.
‘‘. . .any man’s death diminishes me, because I am involved in mankind, and
therefore never send to know for whom the bells tolls; it tolls for thee.’’ —John
Donne, 1624 (published) Devotions upon Emergent Occasions, no. 17 (Meditation)
The book is respectfully dedicated to Dr. Carlo Urbani and those who risk—and far
too often sacrifice—their lives in an attempt to lessen the toll of infectious diseases.
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INFECTIOUS DISEASES: IN CONTEXT
Infectious Diseases: In Context – Finals/ 9/25/2007 11:15 Page 19
A Special Introduction by
Stephen A. Berger, M.D.
The Burden of Infectious Disease in Our Changing,
Globalizing World
As we move into the twenty-first century, we continue to exist in a sea of ancient, hostile
adversaries that threaten our very existence—both as individuals, and as a race of mediumsized mammals. The good news is that modern technology allows us to understand,
diagnose, and treat an expanding number of infectious diseases. The bad news is that this
same modern technology increasingly places us at risk for those same diseases.
For the purpose of clarity, I will classify the infectious diseases of humans into six
broad categories: traditional, new, emerging, re-emerging, disappearing, and extinct. The
latter category is depressingly small, and in fact contains only a single disease. The last case
of smallpox was reported in Somalia in 1977, and the viral agent hibernates (as far as we
know) in secure freezers located in the United States and Russian Federation. The
few disappearing diseases include measles, leprosy, guinea worm, and poliomyelitis—
conditions whose numbers have decreased in recent years, but which could suddenly
blossom into outbreaks when the political and social climate permits.
One must distinguish between ‘‘new diseases’’ and ‘‘newly discovered’’ diseases. The
former category includes conditions that had never before affected mankind: AIDS,
SARS, Ebola. In contrast, Legionnaire’s disease, Chlamydial infection, and Lyme disease
appear to have affected man for many centuries, but were only ‘‘discovered’’ when
appropriate technology permitted.
Emerging diseases such as West Nile fever and Dengue are certainly not new, but
expand both geographically and numerically with the advent of mass tourism and the
dispersal of mosquitoes in suitable animals or other vehicles. As the term implies, ‘‘reemerging’’ diseases such as malaria repopulate areas from which they had been eliminated,
often as the result of man-made alteration of the environment, elimination of natural
predators, global warming, deforestation, and crowding. The best-known disease in this
category is influenza, which is caused by a virus that seems to evolve and mutate
continually into agents that are not recognized by the human host. Even this phenomenon is largely driven by the practice of some human populations to raise swine and ducks
in crowded, unsanitary conditions that promote interchange of viral material.
The vast majority of infectious diseases might be classified as ‘‘traditional,’’ forever
with us and largely unchanged: the common cold, chickenpox, urinary tract infection,
pneumonia, typhoid, gonorrhea, meningitis, and hundreds of others. In some cases,
vaccines have altered the incidence of some traditional diseases among select populations.
In other cases, increasing life span and advances in medical and surgical intervention have
actually created a favorable ecological niche for heretofore non-pathogenic microbes.
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A Special Introduction by Stephen A. Berger, M.D.
Sadly, several new and distressing disease patterns have been the direct result of
advances in managing the infection itself. Tuberculosis has been a largely treatable disease
since the 1940’s; but as of 2007, strains of the causative agent are increasingly resistant to
all known drugs. Highly resistant microbes are now commonplace in cases of AIDS,
malaria, and gonorrhea, as well as many of the traditional bacteria for which antibiotics
were primarily developed: staphylococci, pneumococci and E. coli.
Hopefully, the seemingly self-destructive aspect of mankind will be overtaken by
continued advances in the treatment, prevention, and understanding of the microbes that
share our world.
Stephen A. Berger, M.D.
Director of Geographic Medicine
Tel Aviv Medical Center
Tel Aviv, Israel
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INFECTIOUS DISEASES: IN CONTEXT
Infectious Diseases: In Context – Finals/ 9/25/2007 11:15 Page 21
About the In Context
Series
Written by a global array of experts yet aimed primarily at high school students and an
interested general readership, the In Context series serves as an authoritative reference
guide to essential concepts of science, the impacts of recent changes in scientific consensus, and the effects of science on social, political, and legal issues.
Cross-curricular in nature, In Context books align with, and support, national
science standards and high school science curriculums across subjects in science and the
humanities, and facilitate science understanding important to higher achievement in the
No Child Left Behind (NCLB) science testing. Inclusion of original essays written by
leading experts and primary source documents serve the requirements of an increasing
number of high school and international baccalaureate programs, and are designed to
provide additional insights on leading social issues, as well as spur critical thinking about
the profound cultural connections of science.
In Context books also give special coverage to the impact of science on daily life,
commerce, travel, and the future of industrialized and impoverished nations.
Each book in the series features entries with extensively developed words-to-know
sections designed to facilitate understanding and increase both reading retention and the
ability of students to understand reading in context without being overwhelmed by
scientific terminology.
Entries are further designed to include standardized subheads that are specifically
designed to present information related to the main focus of the book. Entries also
include a listing of further resources (books, periodicals, Web sites, audio and visual
media) and references to related entries.
In addition to maps, charts, tables and graphs, each In Context title has approximately 300 topic-related images that visually enrich the content. Each In Context title will
also contain topic-specific timelines (a chronology of major events), a topic-specific
glossary, a bibliography, and an index especially prepared to coordinate with the volume
topic.
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About This Book
The goal of Infectious Diseases: In Context is to help high-school and early college-age
students understand the essential facts and deeper cultural connections of topics and
issues related to the scientific study of infectious disease.
The relationship of science to complex ethical and social considerations is evident, for
example, when considering the general rise of infectious diseases that sometimes occurs as
an unintended side effect of the otherwise beneficial use of medications. Nearly half the
world’s population is infected with the bacterium causing tuberculosis (TB); although for
most people the infection is inactive, yet the organism causing some new cases of TB is
evolving toward a greater resistance to the antibiotics that were once effective in treating
TB. Such statistics also take on added social dimension when considering that TB
disproportionately impacts certain social groups (the elderly, minority groups, and people
infected with HIV).
In an attempt to enrich the reader’s understanding of the mutually impacting
relationship between science and culture, as space allows we have included primary
sources that enhance the content of In Context entries. In keeping with the philosophy
that much of the benefit from using primary sources derives from the reader’s own
process of inquiry, the contextual material introducing each primary source provides an
unobtrusive introduction and springboard to critical thought.
General Structure
Infectious Diseases: In Context is a collection of 250 entries that provide insight into
increasingly important and urgent topics associated with the study of infectious disease.
The articles in the book are meant to be understandable by anyone with a curiosity
about topics related to infectious disease, and the first edition of Infectious Diseases: In
Context has been designed with ready reference in mind:
• Entries are arranged alphabetically, rather than by chronology or scientific subfield.
• The chronology (timeline) includes many of the most significant events in the
history of infectious disease and advances of science. Where appropriate, related
scientific advances are included to offer additional context.
• An extensive glossary section provides readers with a ready reference for contentrelated terminology. In addition to defining terms within entries, specific Words-toKnow sidebars are placed within each entry.
• A bibliography section (citations of books, periodicals, websites, and audio and visual
material) offers additional resources to those resources cited within each entry.
• A comprehensive general index guides the reader to topics and persons mentioned
in the book.
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About This Book
Entry Structure
In Context entries are designed so that readers may navigate entries with ease. Toward
that goal, entries are divided into easy-to-access sections:
• Introduction: A opening section designed to clearly identify the topic.
• Words-to-know sidebar: Essential terms that enhance readability and critical
understanding of entry content.
• Established but flexible rubrics customize content presentation and identify each
section, enabling the reader to navigate entries with ease. Inside Infectious Diseases:
In Context entries readers will find two key schemes of organization. Most entries
contain internal discussions of Disease History, Characteristics, and Transmission,
followed by Scope and Distribution, then a summary of Treatment and Prevention. General social or science topics may have a simpler structure discussing, for
example, History and Scientific Foundations. Regardless, the goal of In Context
entries is a consistent, content-appropriate, and easy-to-follow presentation.
• Impacts and Issues: Key scientific, political, or social considerations related to the
entry topic.
• Bibliography: Citations of books, periodicals, web sites, and audio and visual
material used in preparation of the entry or that provide a stepping stone to further
study.
• ‘‘See also’’ references clearly identify other content-related entries.
Infectious Diseases: In Context special style notes
Please note the following with regard to topics and entries included in Infectious Diseases:
In Context:
• Primary source selection and the composition of sidebars are not attributed to
authors of signed entries to which the sidebars may be associated. In all cases, the
sources for sidebars containing external content (e.g., a CDC policy position or
medical recommendation) are clearly indicated.
• The Centers for Disease Control and Prevention (CDC) includes parasitic diseases
with infectious diseases, and the editors have adopted this scheme.
• Equations are, of course, often the most accurate and preferred language of science,
and are essential to epidemiologists and medical statisticians. To better serve the
intended audience of Infectious Diseases: In Context, however, the editors attempted
to minimize the inclusion of equations in favor of describing the elegance of thought
or essential results such equations yield.
• A detailed understanding of biology and chemistry is neither assumed nor required
for Infectious Diseases: In Context. Accordingly, students and other readers should
not be intimidated or deterred by the sometimes complex names of chemical molecules or biological classification. Where necessary, sufficient information regarding
chemical structure or species classification is provided. If desired, more information
can easily be obtained from any basic chemistry or biology reference.
Bibliography citation formats (How to cite articles and
sources)
In Context titles adopt the following citation format:
Books
Magill, Gerard, ed. Genetics and Ethics: An Interdisciplinary Study. New York: Fordham
University Press, 2003.
Verlinsky, Yury, and Anver Kuliev. Practical Preimplantation Genetic Diagnosis. New
York: Springer, 2005.
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INFECTIOUS DISEASES: IN CONTEXT
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About This Book
Web Sites
ADEAR. Alzheimer’s Disease Education and Referral Center. National Institute on Aging.
<http://www.alzheimers.org/generalinfo.htm> (accessed January 23, 2006).
Genetics and Public Policy Center. <http://dnapolicy.org/index.jhtml.html> (accessed
January 23, 2006).
Human Genetics in the Public Interest. The Center for Genetics and Society. <http://
www.genetics-and-society.org> (accessed January 26, 2006).
PGD: Preimplantation Genetic Diagnosis. ‘‘Discussion by the Genetics and Public Policy
Center.’’ <http://dnapolicy.org/downloads/pdfs/policy_pgd.pdf> (accessed
January 23, 2006).
Alternative citation formats
There are, however, alternative citation formats that may be useful to readers and examples
of how to cite articles in often used alternative formats are shown below.
APA Style
Books: Kübler-Ross, Elizabeth. (1969) On Death and Dying. New York: Macmillan.
Excerpted in K. Lee Lerner and Brenda Wilmoth Lerner, eds. (2006) Medicine,
Health, and Bioethics: Essential Primary Sources, Farmington Hills, Mich.: Thomson
Gale.
Periodicals: Venter, J. Craig, et al. (2001, February 16). ‘‘The Sequence of the Human
Genome.’’ Science, vol. 291, no. 5507, pp. 1304–51. Excerpted in K. Lee Lerner and
Brenda Wilmoth Lerner, eds. (2006) Medicine, Health, and Bioethics: Essential
Primary Sources, Farmington Hills, Mich.: Thomson Gale.
Web Sites: Johns Hopkins Hospital and Health System. ‘‘Patient Rights and
Responsibilities.’’ Retrieved January 14, 2006 from Http://www.hopkinsmedicine.
org/patients/JHH/patient_rights.html. Excerpted in K. Lee Lerner and Brenda
Wilmoth Lerner, eds. (2006) Medicine, Health, and Bioethics: Essential Primary
Sources, Farmington Hills, Mich.: Thomson Gale.
Chicago Style
Books: Kübler-Ross, Elizabeth. On Death and Dying. New York: Macmillan, 1969.
Excerpted in K. Lee Lerner and Brenda Wilmoth Lerner, eds. Medicine, Health, and
Bioethics: Essential Primary Sources, Farmington Hills, MI: Thomson Gale, 2006.
Periodicals: Venter, J. Craig, et al. ‘‘The Sequence of the Human Genome.’’ Science
(2001): 291, 5507, 1304–1351. Excerpted in K. Lee Lerner and Brenda Wilmoth
Lerner, eds. Medicine, Health, and Bioethics: Essential Primary Sources, Farmington
Hills, MI: Thomson Gale, 2006.
Web Sites: Johns Hopkins Hospital and Health System. ‘‘Patient Rights and
Responsibilities.’’ <http://www.hopkinsmedicine.org/patients/JHH/patient_
rights.html.> (accessed January 14, 2006). Excerpted in K. Lee Lerner and Brenda
Wilmoth Lerner, eds. Medicine, Health, and Bioethics: Essential Primary Sources,
Farmington Hills, MI: Thomson Gale, 2006.
MLA Style
Books: Kübler-Ross, Elizabeth. On Death and Dying, New York: Macmillan, 1969.
Excerpted in K. Lee Lerner and Brenda Wilmoth Lerner, eds. Medicine, Health, and
Bioethics: Essential Primary Sources, Farmington Hills, Mich.: Thomson Gale, 2006.
Periodicals: Venter, J. Craig, et al. ‘‘The Sequence of the Human Genome.’’ Science,
291 (16 February 2001): 5507, 1304–51. Excerpted in K. Lee Lerner and Brenda
Wilmoth Lerner, eds. Terrorism: Essential Primary Sources, Farmington Hills, Mich.:
Thomson Gale, 2006.
INFECTIOUS DISEASES: IN CONTEXT
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Infectious Diseases: In Context – Finals/ 9/25/2007 11:15 Page 26
About This Book
Web Sites: ‘‘Patient’s Rights and Responsibilities.’’ Johns Hopkins Hospital and Health
System. 14 January 2006. <http://www.hopkinsmedicine.org/patients/JHH/
patient_rights.html.> Excerpted in K. Lee Lerner and Brenda Wilmoth Lerner, eds.
Terrorism: Essential Primary Sources, Farmington Hills, Mich.: Thomson Gale, 2006.
Turabian Style (Natural and Social Sciences)
Books: Kübler-Ross, Elizabeth. On Death and Dying, (New York: Macmillan, 1969).
Excerpted in K. Lee Lerner and Brenda Wilmoth Lerner, eds. Medicine, Health, and
Bioethics: Essential Primary Sources, (Farmington Hills, Mich.: Thomson Gale,
2006).
Periodicals: Venter, J. Craig, et al. ‘‘The Sequence of the Human Genome.’’ Science,
291 (16 February 2001): 5507, 1304–1351. Excerpted in K. Lee Lerner and Brenda
Wilmoth Lerner, eds. Medicine, Health, and Bioethics: Essential Primary Sources,
(Farmington Hills, Mich.: Thomson Gale, 2006).
Web Sites: Johns Hopkins Hospital and Health System.‘‘Patient’s Rights and
Responsibilities.’’ available from http://www.hopkinsmedicine.org/patients/JHH/
patient_rights.html; accessed14 January 2006. Excerpted in K. Lee Lerner and
Brenda Wilmoth Lerner, eds. Medicine, Health, and Bioethics: Essential Primary
Sources, (Farmington Hills, Mich.: Thomson Gale, 2006).
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Using Primary Sources
The definition of what constitutes a primary source is often the subject of scholarly debate
and interpretation. Although primary sources come from a wide spectrum of resources,
they are united by the fact that they individually provide insight into the historical milieu
(context and environment) during which they were produced. Primary sources include
materials such as newspaper articles, press dispatches, autobiographies, essays, letters,
diaries, speeches, song lyrics, posters, works of art—and in the twenty-first century, web
logs—that offer direct, first-hand insight or witness to events of their day.
Categories of primary sources include:
• Documents containing firsthand accounts of historic events by witnesses and participants. This category includes diary or journal entries, letters, email, newspaper
articles, interviews, memoirs, and testimony in legal proceedings.
• Documents or works representing the official views of both government leaders and
leaders of other organizations. These include primary sources such as policy statements, speeches, interviews, press releases, government reports, and legislation.
• Works of art, including (but certainly not limited to) photographs, poems, and songs,
including advertisements and reviews of those works that help establish an understanding of the cultural milieu (the cultural environment with regard to attitudes and
perceptions of events).
• Secondary sources. In some cases, secondary sources or tertiary sources may be
treated as primary sources. For example, if an entry written many years after an event,
or to summarize an event, includes quotes, recollections, or retrospectives (accounts
of the past) written by participants in the earlier event, the source can be considered a
primary source.
Analysis of primary sources
The primary material collected in this volume is not intended to provide a comprehensive
or balanced overview of a topic or event. Rather, the primary sources are intended to
generate interest and lay a foundation for further inquiry and study.
In order to properly analyze a primary source, readers should remain skeptical and
develop probing questions about the source. Using historical documents requires that
readers analyze them carefully and extract specific information. However, readers must
also read ‘‘beyond the text’’ to garner larger clues about the social impact of the primary
source.
In addition to providing information about their topics, primary sources may also
supply a wealth of insight into their creator’s viewpoint. For example, when reading a
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Using Primary Sources
news article about an outbreak of disease, consider whether the reporter’s words also
indicate something about his or her origin, bias (an irrational disposition in favor of
someone or something), prejudices (an irrational disposition against someone or something), or intended audience.
Students should remember that primary sources often contain information later
proven to be false, or contain viewpoints and terms unacceptable to future generations.
It is important to view the primary source within the historical and social context existing
at its creation. If for example, a newspaper article is written within hours or days of an
event, later developments may reveal some assertions in the original article as false or
misleading.
Test new conclusions and ideas
Whatever opinion or working hypothesis the reader forms, it is critical that they then test
that hypothesis against other facts and sources related to the incident. For example, it
might be wrong to conclude that factual mistakes are deliberate unless evidence can be
produced of a pattern and practice of such mistakes with an intent to promote a false idea.
The difference between sound reasoning and preposterous conspiracy theories (or
the birth of urban legends) lies in the willingness to test new ideas against other sources,
rather than rest on one piece of evidence such as a single primary source that may contain
errors. Sound reasoning requires that arguments and assertions guard against argument
fallacies that utilize the following:
• false dilemmas (only two choices are given when in fact there are three or more
options);
• arguments from ignorance (argumentum ad ignorantiam; because something is not
known to be true, it is assumed to be false);
• possibilist fallacies (a favorite among conspiracy theorists who attempt to demonstrate that a factual statement is true or false by establishing the possibility of its truth
or falsity. An argument where ‘‘it could be’’ is usually followed by an unearned
‘‘therefore, it is.’’);
• slippery slope arguments or fallacies (a series of increasingly dramatic consequences is
drawn from an initial fact or idea);
• begging the question (the truth of the conclusion is assumed by the premises);
• straw man arguments (the arguer mischaracterizes an argument or theory and then
attacks the merits of their own false representations);
• appeals to pity or force (the argument attempts to persuade people to agree by
sympathy or force);
• prejudicial language (values or moral goodness, good and bad, are attached to certain
arguments or facts);
• personal attacks (ad hominem; an attack on a person’s character or circumstances);
• anecdotal or testimonial evidence (stories that are unsupported by impartial observation or data that is not reproducible);
• post hoc (after the fact) fallacies (because one thing follows another, it is held to cause
the other);
• the fallacy of the appeal to authority (the argument rests upon the credentials of a
person, not the evidence).
Despite the fact that some primary sources can contain false information or lead
readers to false conclusions based on the ‘‘facts’’ presented, they remain an invaluable
resource regarding past events. Primary sources allow readers and researchers to come as
close as possible to understanding the perceptions and context of events and thus to more
fully appreciate how and why misconceptions occur.
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INFECTIOUS DISEASES: IN CONTEXT