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Epidemiology Notes
Definition: ______________________________________________________________________
_______________________________________________________________________________
Epidemiology – What is it?
 The study of the ___________________________________________________________
____________________________ disease, disability, and death in human populations.
 Also involves characterizing the distribution of heath status, diseases, or other health problems
in terms of _________________________________________________________________
_______________
 This characterization is done in order to explain the _________________________________
___________________________ in terms of the causal factors
 Serves as the foundation and logic of interventions made in the interest of _______________
_____________________________________________________.
 ____________________________ of public health research
 ____________________________________ for identifying risk factors for disease
 Used to determine ___________________________________approaches to clinical practice.
 In the work of communicable and non-communicable diseases, the work of epidemiologists
range from ___________________________________________________________
___________________________________________________ and the documentation of
results for submission to peer-reviewed journals.
 ______________________ may draw on a number of other scientific disciplines such as
biology in understanding disease processes and social science disciplines including sociology
and philosophy in order to better understand proximate and distal risk factors
History
 The Greek physician _____________ is sometimes said to be the father of epidemiology. He
is the first person known to have examined the relationships between the occurrence of
disease and environmental influences.
 He coined the terms _____________ (for diseases usually found in some places but not in
others) and __________________ (for disease that are seen at some times but not others).
 One of the earliest theories on the origin of disease was that it was primarily the ___________
_____________. This was expressed by philosophers such as Plato and Rousseau, and social
critics like Jonathan Swift
 In the medieval Islamic world, physicians discovered the contagious nature of infectious
disease. In particular, the Persian physician Avicenna, considered a "father of modern
medicine," in _______________________ ______), discovered the contagious nature of
tuberculosis and sexually transmitted disease, and the distribution of disease through water
and soil.
 Avicenna stated that bodily secretion is contaminated by ___________________ before being
infected. He introduced the method of _____________ as a means of limiting the spread of
contagious disease.
 He also used the method of risk factor analysis, and proposed the idea of a syndrome in the
diagnosis of specific diseases.
 When the Black Death (____________) reached Al Andalus in the 14th century, Ibn Khatima
hypothesized that infectious diseases are caused by small "minute bodies" which enter the
human body and cause disease. Another 14th century Andalusian-Arabian physician, Ibn alKhatib (1313–1374), wrote a treatise called On the Plague, in which he stated how infectious
disease can be transmitted through bodily contact and "through garments, vessels and
earrings."
 In the middle of the 16th century, a famous Italian doctor from Verona named Girolamo
Fracastoro was the first to propose a theory that these _______________________________
that cause disease were alive. They were considered to be able to spread by air, multiply by
themselves and to be destroyable by fire. In this way he refuted Galen's theory of __________
(poison gas in sick people). In 1543 he wrote a book De contagione et contagiosis morbis, in
which he was the first to promote ________________________________________________.
 The miasmatic theory of disease held that diseases such as cholera or the Black Death were
caused by a miasma (Greek language: "pollution"), a _________________. In general, this
concept has been supplanted by the more scientifically founded _______________________.
 The development of a sufficiently powerful microscope by Anton van Leeuwenhoek in 1675
provided visual evidence of living particles consistent with a __________________________.
 John Graunt, a professional ___________________ and serious amateur scientist, published
Natural and Political Observations ... upon the Bills of Mortality in 1662.
 He used analysis of the mortality rolls in London before the ____________ to present one of
the first _________ and report time trends for many diseases, new and old.
 He provided ____________________ for many theories on disease, and also refuted many
widespread ideas on them.
 Dr. John Snow is famous for his
________________________ of the science of
investigations into the causes of the
epidemiology.
19th Century _________ __________.
He began with a comparison between
the ___________ from areas supplied
by two
____________________________ in
Southwark. His identification of the
Broad Street pump as the cause of the
Soho epidemic is considered the classic
example of epidemiology.
 He used chlorine in an attempt to clean
the water and had the handle removed,
thus ending the outbreak. (It has been
questioned as to whether the epidemic
was already in decline when Snow took
action.)
 This has been perceived as a major
event in the history of public health and
can be regarded as the
 Other pioneers include Danish physician P. A. Schleisner, who in 1849 related his work on the
prevention of the epidemic of __________________ on the Vestmanna Islands in Iceland.
Another important pioneer was Hungarian physician Ignaz Semmelweis, who in 1847 brought
down infant mortality at a Vienna hospital by instituting a _____________________ procedure.
 His findings were published in 1850, but his work was ill received by his colleagues, who
discontinued the procedure. Disinfection did not become widely practiced until British surgeon
Joseph Lister 'discovered' antiseptics in 1865 in light of the work of Louis Pasteur.
 In the early 20th century, _______________________________ were introduced into
epidemiology by Ronald Ross, Anderson Gray McKendrick and others.
Purposes of Epidemiology
 To explain the _______________ ______ of a single disease or group of diseases using
information management
 To determine if data are consistent with _________________ To provide a basis for developing control measures and prevention procedures for groups and
at risk populations
Terms to know
 Disease __________________________________________________________________
_________________________________________________________________________
 also – an abnormal state in which the body is not capable of responding to or carrying
on its normally required functions
 Pathogens _________________________________________________________________
_________________________________________________________________________
 Pathogenesis _____________________________________________________________
 Pathogenic _____________________________________________________________
 Pathogenicity______________________________________________________________
_________________________________________________________________________
 Infective __________________________________________________________________
_________________________________________________________________________
 Virulence _____________________________________________________________
 _____________________________________________________________
 the capacity and strength of the disease to produce severe and fatal cases of illness
 Invasiveness _______________________________________________________________
_________________________________________________________________________
 Etiology _____________________________________________________________
 Toxins __________________________________________________________________
_________________________________________________________________________
 notably toxic when introduced into the tissues, and typically capable of inducing
antibody formation
 Antibiotics _______________________________________________________________
_________________________________________________________________________
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 endemic: _____________________________________________________________
 hyperendemic: _____________________________________________________________
 holoendemic: _______________________________________________________________
_________________________________________________________________________
 epidemic: _________________________________________________________
_________________________________________________________________________
 pandemic: _________________________________________________________
_________________________________________________________________________
 incidence: _________________________________________________________
_________________________________________________________________________
 prevalence: _________________________________________________________
_________________________________________________________________________
 point prevalence: _________________________________________________________
_________________________________________________________________________
 How many people have had the disease in the past
 Duration of the disease in the population
7 Uses of Epidemiology
1. To study the _________________________
 Studies trends of a disease for the _______________________
 Results of studies are useful in __________________________________________
2. Community diagnosis
 What ___________________________________________________________________
_____________________________________________
3. Look at risks of __________________ as they affect _________________________
 What are the risk factors, problems, behaviors that ________________
 Groups are studied by doing ____________________________
4. Assessment, evaluation and research
 How well do public health and health services ______________________________________
 Effectiveness; efficiency; quality; access; availability of services to treat, control or prevent
disease
5. Completing the clinical picture
 Identification and diagnostic process to establish that a _______________________________
________________________
 Cause effect relationships are determined, e.g. _____________________________________
6. Identification of syndromes
 Help to establish and _______________________________, some examples are: Down, fetal
alcohol, sudden death in infants, etc.
7. Determine the _____________________________________________
 Findings allow for control prevention, and elimination of the causes of disease, conditions,
injury, disability, or death
The Epidemiology Triangle
 Outbreaks in a population often involves several factor and entities
 Many people, objects, avenues of transmission, and organisms can be _________________
________________________________
 Epidemiologist have created a model to help explain the multifaceted phenomena of disease
transmission: _____________________________________
 Many diseases rely on an _______________ or single factor for an infectious disease to occur.
 Epidemiologist use an _____________________________ to assess the interaction of various
elements and factors in the _____________________________________________________
 When more than a ____________________ must be present for a disease to occur, this is
called _________________________
The interrelatedness of 4 factors contribute to the outbreak of a disease
1. _____________________________
2. _____________________________
3. _____________________________
4. _____________________________
 The epidemiology triangle is used to analyze the role and interrelatedness of each of the four
factors in epidemiology of infectious diseases, that is the influence, reactivity and effect each
factor has on the other three
 The___________________ is the cause of the disease
 Can be ___________________________________________________________
 __________________________________________________________________
 The _________ is an organism, usually human or animal, _________________________
 _____________________ disease-causing _______________________ or related substance
 Offers subsistence and lodging for a _____________________
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
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


 __________________________________________________________________
within the host can determine the effect of a disease organism can have upon it.
The _____________________________ is the favorable surroundings and conditions external
to the human or animal that ___________________________________________________
 Environmental factors can include the _____________________ as well as the
__________________________________________________________________
Time accounts for _____________________________, ______________ of the host or
pathogen, ______________________________ of illness or condition.
The mission of the epidemiologist is to ________________________________, which disrupts
the connection between ______________________________________ stopping the
continuation of an outbreak.
The goals of public health are the ______________________________________________.
By ____________________________________________, public health intervention can
partially realize these goals and stop epidemics
An epidemic can be stopped when one of the elements of the triangle is
___________________________________________________________________.
Disease Transmission
 ____________________ inanimate objects that serve as a role in disease transmission
 ____________________________________
 __________________ any living non-human carrier of disease that transports and serves the
process of disease transmission
 _________________________________________
 ___________________ humans, animals, plants, soils or inanimate organic matter (feces or
food) in which infectious organisms live and multiply
 _____________________ often serve as reservoir and host
 ______________________ when a animal transmits a disease to a human
 __________________________ one that spreads or harbors an infectious organism
 Some carriers may be infected and not be sick. e.g. Typhoid Mary
 Mary Mallon (1869 – 1938) was the first person in the United States to be identified as
a healthy carrier of typhoid fever. Over the course of her career as a cook, she infected
47 people, three of whom died from the disease.
 Her notoriety is in part due to her ___________________ denial of her own role in
spreading the disease, together with her refusal to _____________________________.
 She was forcibly quarantined twice by public health authorities and died in quarantine. It
is possible that she was born with the disease, as her mother had typhoid fever during
her pregnancy.
 ___________________ individual exposed to and harbors a disease-causing organism. May
have recovered from the disease
 ___________________ exposed to and harbors disease-causing organism (pathogen) and is
in the recovery phase but is still infectious
 ___________________ exposed to an harbors pathogen, has not shown any symptoms
 ____________________ exposed to and harbors a disease and is in the beginning stages of
the disease, showing symptoms, and has the ability to transmit the disease
 ___________________ exposed to and harbors disease and can intermittently spread the
disease
 _____________________ exposed to and harbors disease causing organism, but has no
signs or symptoms
Modes of Disease Transmission
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 methods by which an ___________________________________________ to the next
 or can ____________________________________________ (either person or animal)
Two general modes
 ________________
________________
_________________________ or person to person
 Immediate transfer of the pathogen or agent
_________________________ or person to person
 Immediate transfer of the pathogen or agent from a ____________________________
 Can occur through direct physical contact or direct personal contact such as
_______________________________________________________
___________________________
 pathogens or agents are transferred or carried by some ________________________,
means or process to a susceptible host
 done in one or more following ways:
 _______________________________________
 _______________
 _________________________ carry the pathogen to the host and infect it
 ________________________________ all spray microscopic droplets in the air
 ________________
 Carried in _______________________ streams or lakes used for swimming.
Examples: ______________
 Vehicleborne
 Related to _________________
 Vectorborne
 A pathogen uses a _____________________________________ as a
mechanism for a ride or nourishment this is mechanical transmission
 _______________________________ when the pathogen undergoes changes
as part of its life cycle, while within the host/vector and before being transmitted
to the new host
Chain of Transmission
 Close association between the triangle of epidemiology and the chain of transmission
 Disease transmission occurs when the ____________________ leaves the
_________________ through a ________________ and is spread by one of several
_______________________________
 _______________ in the chain of transmission will _______________________________
Classes of Outbreaks
 Common Source Epidemic – when a _______________________ is exposed to a common
___________________________
 Point source from a single source (food)
 Persons exposed in ______________________________ and become ill within
the _______________________ Ex: ________________________________________
 Intermittent ____________________________________
 _______________________ spread by person to person contact and people
move around and interact with other people
 Continuous epidemic
 When an epidemic spreads through a ___________________________ at a
high level, affecting a large number of people within the population ___________
 Propagated Epidemic when a single source ______________________, yet the epidemic or
diseases continues to spread from __________________________
 Usually experiences exponential growth
 Cases occur over and over longer than one incubation period
 Mixed Epidemic a __________________________ is followed by ___________________
contact and the disease is spread as a ________________________________
Levels of Disease
Diseases have a range of ___________________________________________________________
Classified into 3 levels
 Acute _____________,_______________________________________________________
 usually the patient ___________________________
 Subacute intermediate in _______________________, having some acute aspects to the
disease but of longer duration and with a degree of severity that detracts from a _______
_____________________
 Patient expected to _________________________
 Chronic less severe but of ____________________________________, lasting over
________________________________________________________ Patient may not fully recover and the disease can get worse overtime
 Life not immediately threatened, but may be over long term
Immunity and Immunization
 History
 Before polio vaccine became available in 1955, _____________ cases of polio occurred
in peak years. ½ of these cases resulted in permanent paralysis
 Prior to measles vaccine in 1963, ___________________________ cases per year
 Immunization of 60 million children from 1963-1972 cost ________________, but saved
_________________
 Mumps used to be the leading cause of__________________________
 10% of children with _____________________________
 According to CDC, unless ____ or greater of the population is vaccinated, ______________
can occur
 Three types of immunity possible in humans
 Acquired Immunity obtained by having __________________________________
____________________________________ or artificially stimulating immune system
 Active Immunity body produces _________________________
 can occur through a _______________________________________________
_______________
 Similar to acquired
 Passive Immunity (natural passive) acquired through ___________________
transfer of a mother’s immunity to diseases to the unborn child (also _______________)
 can also come from the introduction of already __________________________
into a susceptible case
When there is little to no immunity within a population, ____________________________________
Herd Immunity
 the resistance ____________________________________ has to the invasion and spread of
an infectious disease
Disease for which vaccines are used
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Antrhax
Chicken pox
Cholera
Diphtheria
German
measles
(rubella)
Hepatitis A & B
HPV
Influenza
Malaria (in
process)
Measles
Menigitis
Mumps
 Plague
 Pneumonia
 Polio
 Rabies
 Small pox
 Spotted fever

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Tetanus
Tuberculosis
Typhoid Fever
Typhus
Whooping
Cough
 Yellow Fever