Epidemiology Flashcards
Study of disease, injury and death
Epidemiology
According to CDC, it is the study
(scientific, systematic, and data-driven) of
the distribution and determinants of
health-related states and events (not
just disease) in specified populations
(neighborhood, school, city, state, country, global)
According to WHO, it is the study of
the distribution and determinants of
health-related states or events
(including disease), and the application
of this study to the control of diseases
and other health problems
Epidemiology
Refers to descriptive epidemiology
When (time), Where (place), Who
(person)
Distribution
incidence, prevalence
and mortality rates
Frequency
- time, place, person
Pattern
Refers to analytic epidemiology
Causes, risk factors, modes of
transmission (why and how)
Causes - agents
Risk factors - exposure to sources
Examples: smoking, obesity, high blood
pressure, diabetes, infections, genetics
Determinants
Veni, vidi, vici
(I came, I saw, I conquer)
Theory of four body humors produced
within the body
Earth - blood and brain
Air - phlegm and lungs
Fire - black bile and spleen
Water - yellow bile and gallbladder
Hippocrates (460 BCE - 370 BCE)
Seeds of disease
Girolamo Fracastoro (Circa 1476 - 1553)
Disease as an external thing called an
ens which could attack any organ of the
body
Paracelsus and JB van Helmont
First to demonstrate microorganisms
Antoni van Leeuwenhoek (1632 - 1723)
Germ Theory, germ cause disease
Developed vaccine against anthrax and
biological treatment for rabies
Louis Pasteur (1822 - 1895)
one germ can cause
one disease
Biological specificity
Perfected methods for growing pure
colonies of bacteria
Developed autoclaves for sterilizing
equipment
Introduced photography to demonstrate
what he had seen through his microscope
Identified some of the key disease-
Robert Koch (1843 - 1910)
Antiseptic surgery which developed into
aseptic surgery
Joseph Lister (1827 - 1912)
Named the disease syphilis in a poem
Notion of seeds of disease
Girolamo Fracastoro (1476
His study on cholera reinforced his notion
that it was not transmitted by miasma
but through contaminated water
John Snow (1813 - 1858)
First thorough notion of a germ theory
of disease
Studied yeast, bacteria, and viruses
Louis Pasteur (1882
Use of carbolic acid dressings to
disinfect surgical wounds
Introduced aseptic technique
Joseph Lister (1827
Discovered causative organisms of
tuberculosis and cholera
Robert Koch
Study led to a better understanding of the
nature of viruses and their relationship
to the cells of the organism they
invade
Martinus Beijerinck
Influenced microscopy, tissue staining, embryology, chemotheraphy and
immunology
Theory of the chemical nature of
antigens and antibodies (lock and key)
Paul Ehrlich (1854 - 1915)
Developed a polio vaccine that used an
attenuated strain of the virus
Albert Sabin (1906
Coined the term prion and came up with
the theory behind how these misfolded
proteins cause grave disease
Stanley Prusiner (1942)
Worked on the retroviruses, of which
HIV is the most significant
Francoise Barre-Sinoussi (1947)
–
includes the study of the frequency, patterns, and causes of health-related
states or events in populations, and the
application of that study to address public
health issues
Basic science of public health, epidemiology
Microbes: bacteria, virus, fungi, protozoa
Agent
The human capable of developing the
disease: genetics, ethnicity, socioeconomic status, sex, and
gender
Host
- Lead and heavy metals
- Air pollutants and other
asthma triggers
Environmental exposures
- Foodborne illness
- Influenza and pneumonia
Infectious diseases
- Increased homicides in a
community
- National surge in
domestic violence
Injuries
- Localized or widespread
rise in a particular type of
cancer
- Increase in a major birth
defect
Non-infectious disease
- Hurricanes Katrina and
Rita (2005)
- Haiti earthquake (2010)
Natural disasters
- World Trade Center
(2001)
- Anthrax release (2001)
Terrorism
widely use
Describes the basic epidemiology of a
disease
Descriptive
Used to study the disease further
Analytic
Test a hypothesis
Experimental
Describe the occurrence of the disease
Data collected by time, place, and person
Descriptive Epidemiology
describes the occurrence of
disease over a prolonged period (years)
Trend of tetanus in the United States
since 1920 shows a gradual and steady
decline
Secular
indicate a change in the antigenic
characteristics of the disease agent
Change in antigenic structure of the
prevalent influenza A virus every 2 to 3
years
Periodic
Food-borne disease outbreaks occur
more frequently in the summer
Seasonal
A sudden increase in occurrence due
to prevalent factors
Epidemic occurence of disease
the level of influenza
activity that signalled the start and end of
the annual influenza season
Seasonal Threshold
the week in which positivity
rate was above the weekly average positivity rate for that year and which
continued for three consecutive weeks
Start/onset
- first week in which the positivity
rate was below the average weekly
positivity rate for that year which
continued for three consecutive years
End
the period in which weekly influenza
positive rates were above the average
influenza positivity rate for a particular
surveillance year for at least three
consecutive weeks
Influenza season
the level above which influenza activity
was higher than most years
Alert threshold
Sites or places to consider
Where the individual was when disease
occurred
Where the individual was when he or she
became infected from the source
Where the source became infected with the
etiologic agent
Epidemiologic Data by Place
Age
Sex
Occupation
Personal habits
Socioeconomic status
Immunization history
Presence of underlying disease
Epidemiologic Data of Infected Person
Analyzes disease determinants for
possible causal relations
Analytic Epidemiology
Starts with the effect (disease) and
retrospectively investigates the cause that led
to the effect
Case-control or Case Comparison
individuals with the disease
Case group
members
similar to the case group without the
disease
Comparison (control) group
Prospectively studies two populations
Cohort Method
had contact with the
suspected causal factor (blood
transfusion) under study
Population 1
similar group that has had
no contact with the factor
Population 2
To determine the relationship between a
disease and variables present
A population is surveyed over a limited
time period
Cross-sectional
One or more selected factors are
manipulated
The effect of the manipulation will either
confirm or disprove the hypothesis
Group 1 with the disease - given a new
drug
Group 2 with the disease - not given the
new drug
Experimental Epidemiology
Identify factors relevant to an outbreak
Identify control and prevention measures
Data are collected and collated according to
time, place, and person and analyzed and
inferences are drawn
Epidemiologic Investigation
Steps:
1. Confirm the existence of the epidemic
2. Look for cases, verify diagnosis - case
definition
Confirmed, suspected, probable case
3. Identify population at risk
4. Develop hypothesis
5. Develop control and prevention measures
6. Continue surveillance activities
Epidemiologic Investigation
living organisms or nonliving
sites (soil, water)
Reservoirs
an individual capable of
transmitting a pathogen without displaying
symptoms
Carriers
harbors and transmit
the pathogen but is not infected
Passive carriers
infected and transmit
the pathogen (symptomatic or
asymptomatic)
Active carriers
person to person transmission
(touching, kissing, sexual
Direct
one meter or less distance
Droplet transmission
involves inanimate objects
called fomites
Indirect
transmission of
pathogens through vehicles such as water,
food, air
Aerosols float in the air
Droplet nucleus can travel long
distances
Vehicle Transmission
Vector Transmission
Refers to the occurrence of new cases of
disease or injury in a population over a
specified period of time
Although some epidemiologists use incidence
to mean the new number of new cases in a
community
Others use incidence to mean the number of
new cases per unit of population
Incidence of Disease
Defined as any departure, subjective or
objective from a state of physiological or
psychological well-being
In practice, morbidity encompasses
disease, injury and disability
Morbidity
The relative magnitude of two quantities
or a comparison of any two values
Calculated by dividing one interval or ratio
scale variable by the other
The numerator and denominator need not
be related
Ratio
Comparison of a part to whole
Its numerator is included in the
denominator
Proportion
A measure of frequency with which an
event occurs in a defined population over
a specified period of time
Rates
