EPIDEMIOLOGY MIOLOGY IS -IS THE BASIC SCIENCE USED TO

OBJECTIVES
.Differentiate between observational and
experimental studies
.Describe three types of observational
studies
.Identify the major elements of the
epidemiologic triad model
OBJECTIVES
eories of disease causation
.Identify at least 3 criteria for
determining causality in a relationship
between 2 events
.Define risk
.Distinguish between morbidity and
mortality rates
.Calculate rates and determine their
significance
.Describe the web of causation model
.Describe the 4 major components of
Dever's epidemiologic model
EPIDEMIOLOGY
MIOLOGY
-IS THE BASIC SCIENCE
OF PUBLICHEALTH
USED TO
DIAGNOSE
TREAT
IS
AND
THE
COMMUNITY
Epidemiology
FINITION
-EPI-upon
DEMOS-determine
"..
...
.The study of the dIstrIbutIon of
health and illness within the
population and the fa~to~s that
the population s health
status.
p eo p le
-LOGOS-study
1
,
",
PURPOSES OF
EPIDEMIOLOGY
The Ultimate
..ology
Goal of
is to:
1. To search for causal relationships
in health and illness
.PREVENTDISEASE
.MAINTAIN HEALTH
2. To control illness through the
resultant understanding of
causality
.Prevent PrematureMortality
.Decrease Years of Potential Life Lost
YPLL
Propoltional distribution of deaths
from Infectious and major
ABULARY
.Communicable
or
infectiousdisease:
~
.:
'ousdiseasesin US
::.=.-
t8
8
The
I f
Death
.
Rate
t..
t811
from
.
t
D .Death
n e~ IOUS Isease
in the United States from
1980 to
Rate from Infectious
in the US (per
100 000)
1992
I
48
has increased
from
::
6 to 38
:
deaths per 100,000
::
TheMiamiHerald1/17/96
.
8
t-
t..2
2
Influences of this trend
.Disru
VOCABULARY
tion in environmental habitats
.Microbial adaptation-drug resistance
.Expanded international travel
.Unsafe sexual habits
.Increased frequency of environmental
disasters
E
.conomlc
~
...
Impoverls
h
-Morbidity
Mortality
.Incidence
Prevalence
-nE
t
men
demlc"
.Eliminated
POLIO CASES IN THE US
711e
MiamiHerald5/19/01
350,IlOO
300,IlOO
40
35
30
25
lo~
~I
100,IlOO
21
15
11
1-
5
0
2.-
1-
Guinea Worm Infections
Worldwide
3,001'2,510'-
2.-
CAUSE
"I
IneurterCenter5/15/00
3.511.-
""
~" &?j
/ ..
.
'
..
2,001'1,511'1,000.I
Eradicated
--::
200,IlOO
150,000
500.-
Pan demlc;
"
NUMBER OF COUNTRIES
0 IS ENDEMIC
250,000
50,100
0
EpI"demlc"
10_t-1
!01..CII888
-\
V
\
t_-
3
MIOLOGY
~rnm
I
l!1Jl!PJjlSJUU
I
b
sase
d
h
t
at
result
th
on
one
event
of
another
e
.d
I ea
.of
IS the
event
.
s an ancien
People
have
t
.
science.
been
trying
for
thous<Jlnds
years to determine
disease. Supernatural
what cause:s
events
were the 1st factors
used to explain
disease causation.
Historical
Theories
Development
of Disease
of
Theories
usation
Disease
usation
8 Religious theories-disease is due to
the will of God as a test of faith or
as punishment for sins (2000-600
b.c.)
8 Environmental theories-disease
to harmful miasma or other
substances in the environment
of
is due
(400
.460-377
b.c
epidemiologist
tried
Hippocrates-1st
to exp Iain disease
causation
on a rational
pointing
to environment
lifestyle
basis,
and
b.c.)
.JOHN
SNOW
8 England, 1850's wrote the classical
epidemiological study. He provided a
scientific base for systematically
studying disease distribution.
8 He was able to determine the
origination of cholera
8 The cholera vibrio was not isolated
until 30 years later by Koch.
Theories of Disease
usation
8 Bacteriologic theories-disease
to the action of harmful
microorganisms (1870-1900)
is due
.Era of multiple causation-Disease is
due to the interaction of multiple
factors (1900-present)
4
DnDn~-
STRENGTH OF
Cons i stency
ASSOCIATION
when the cause is present
the effect occurs
I
I
and when the cause is absent I
the effect does not occur
I -~1!~LEJ1!ll
Specificity
the greater the correlation
between the occurrence
of the factor and the health
condition, the greater the
possibility that the relationship
is one of cause and effect
~:iJ.u"::J~JJ.,Temporal relationship
The factor in question results
in one specific condition
The cause occurs before the
effect and not vice versa
@rrf1~@O"d@
fJ@[f @@C!D@@~bnl'l~
jW
.Coherence
The Idea of causality is
congruent with scientific,
knowledge in this area
RI S K
5
-
RISK
RISK
.The probability that a
given individual will
deve~o~ a specific
condition
-Increase
one's
likelihood of death,
disease, injury or
psychosocial
conditions
One's risk is affected
by a
variety of factors including
.physical
POPULATIONS
AT
RISK
.lifestyle
..Groups
.emot'~nal
.behavioral
of people who have the
greatest potential to develop
a particular problem because
.environmental
of the presence or absence of
.genetic
certain contributing factors:.
BASIS
FOR RISK
.SUSCEPTIBILITY
an
d/
.The ability to be
affected by factors
contributing
particular
or
.POTENTIAL
EXPOSURE
SUSCEPTIBILITY
FOR
to a
health
condition.
6
EXPOSURE
ENTIAL
.The
likelihood
of
exposure to factors
that contribute
to the
condition
RELATIVERISK RATIO
.The difference in the
p~obability..of developinga
given condition between
membersof a populationof risk
for developingthat condition
and tho~e individualswho are
not at risk.
RATES OF
RATE
5
URENCE
.Statistical measures that
indicate the extent of health
problems in a group
RATES
RATES OF
URENCE
.Allow comparisonsbetween
groups of different sizes with
respect to a particular
condition.
.Event
.Time
.ace
PI
7
Rates
A TES
Numberof Instancesof an Eventin
a CertainPlaceat a CertainTime
-Multiply
by 1000 or
;~;U~~;i:~
-a~
-~i~~-i~-~~~;~;:c~-~; -100,000
that Time
TYPES OF RATES
tal ity Rates
.The ratio of the number of
deaths in various categories
to a given population
-MORTALITY
-MORBIDITY
Crude Death Rate
Total number of
deaths during year
Cause-specific annual
ath rate
Numberof deaths from
a specific cause during year
X 1000
Total population at
X 11000
Total populationat midyear
midyear
8
Example
Infant Mortal ity Rate
f d
h
eat s
due to cervical cancer
in Cincinnati in 1999
Numberof deaths during
Y
(be.ar
Irt h to one year of age)
X 1000
Number of women in
Cincinnati in 1999
Infant
Mortal
X 1000
Number of live births
during year
ity
Infant MortalityRatesUSand
t
FL
a es
1970-1995
IS
.The
measure
most commonly
usedaroundthe worldas an
indicatorof overallhealthand
availabilityof healthservices
18
1.
11
.
1
1818
1178
1.. 1.. 1.. 1.-
Case Fatality
~
Rate
.Reflects
the percentage of
people with a certain
condition who die as a result
of it
9
-
.ity
Rates
-The ratio of the
ORBIDITY
RATES
.
number of cases of a
.Incldence
disease or condition to
a given population
.Prevalence
.ExampleRate
Annua I Incidence
Number
of New Cases
of a Condition
Number of new cases
last year
of cervical cancer in
X 1000
Total Population
at M od
I year
Cincinnati in 1999
at Risk
X 1000
Number of women in
Cincinnati in 1999
Annual Prevalence
Example
Rate
Total Number of Cases
of a Condition last year
X 1000
Total Population at Risk
at Midyear
Number of cases of
cervical cancer in
Cincinnati in 1999
X 1000
Number of women in
Cincinnati in 1999
10
Survival
Rate
.The
proportion
with a certain
..
'
0
HEALTH ST ATISTICS
of people
condition
ft
remaining a lye a er a
fo
.
speci IC perlo d ( usua II y
O
5
years)
-data that delineate
health or population events
.Vital Statistics-birth. adoption.
death. marriage. divorce
"
..
.Mortality statistics-death trends
M b"d " ty t t . t .
.or
I I S a IS Ics-ex t ent 0f
illness. disability
.Demographic statisticscharacteristics of populations
Other important rates
SOURCES OF
AT A
.Employment rates
.Rates of alcohol. drug use and
abuse
.Utilization rates of health care
services
.Marriage. divorce rates
.Literacy rates
.Population
.Morta
M
.or
I "fty
b "d "
I
I
ty
.Immunization rates
REPORTABLE
10 MOST FREQUENTLY
DISEASES
REPORTEDINFECTIOUS
IN THE US 1995
.Animal bite
.Anthrax
.Botulism
.Brucellosis
1.
2.
3.
4.
Chlamydia 477,638
Gonorrhea 392,848
AIDS 71,547
Salmonellosis 45,970
.Campylobacteriosis
.Cancer
(except non-Melanoma skin cancer)
.Olancroid
5.
6.
7.
8.
Hepatitis A 31,582
Shigellosis 32,080
TB 22,860
Syphilis 16,500
.Ollamydia
.Oguatera
.aytosporidiosis
9. Lyme Disease 11,700
10. Hepatitis B 10,805
the Miami Herald 10/19/96
11
.
~
Major Indicators of Health
.Life
expectancy
*Infant
I
.Health
#1
#2
#3
#4
#5
DMBIe
DFenaIe
10
I ty
10 0
behavior
DEATH
~
40
30
mortality
LEADING
www.origina/ghrl~com
so
mortality
b od °
.Mor
IN
:
causes of death
*Maternal
THE US
80
.Mortality
*Leading
LIFE EXPECTANCY
1..
CAUSES
OF
LEADING
1993-95
Congenital Anomalies
Short Gestation
SIDS
Respiratory Distress Syndrome
Maternal Complications
118
DEATH
I-.
u.
CAUSES OF
1993-5
ge # Unintentional Injuries
#2 Congenital Anomalies
#3 Malignant Neoplasms
#4 Homicide
#5 Heart Disease
.
#7 Injuries
#6 HIV
#8 Perinatal Infections
#7 Pnuemonia & Influenza
#9 Pheumonia & Influenza
LEADING
DEATH
CAUSES OF
1993-5
Ages 5-9
#1 Unintentional Injuries
#2 Malignant Neoplasms
#3
#4
#5
#6
#7
LEADING
Congenital Anomalies
Homicide
Heart Disease
HIV
Pnuemonia & Influenza
DEATH
CAUSES OF
1993-5
ges
#1 Unintentional Injuries
#2 Malignant Neoplasms
#3 Homicide
#4
#5
#6
#7
Suicide
Congenital Anomalies
Heart Disease
Bronchitis, Emphysema, Asthma
12
LEADING
CAUSES OF
DEATH
1993-5
Injuries
#2 Homicide
Neoplasms
Disease
Neoplasms
Disease
Neoplasms
#3 Unintentional
Injuries
Disease
#2
Heart
Neoplasms
Disease
#3 Unintentional
#4
Injuries
HIV
#5 Suicide
#5 Cerebrovascular
#6 Homicide
#6 Suicide
#7 Liver Disease
#7 Diabetes
LEADING CAUSES OF
DEATH 1993 -5
#1
#2
#3
#4
Malignant Neoplasms
Heart Disease
Bronchitis, Emphysema, Asthsma
Cerebrovascular
#5 Diabetes.
#6
#7
#8
#9
accidents
LEADING CAUSES OF
DEATH 1993-5
Ages 45-54
#1 Malignant
Malignant
Heart
Malignant
#6 Heart
ges
#1 HIV
#4
#5
#7 Cerebrovascular
LEADING CAUSES OF
DEATH 1993-5
#2
Injuries
#2 HIV
#4 Suicide
#4 Malignant
HIV
1993-5
#3 Homicide
#3 Suidide
Heart
DEATH
#1 Unintentional
#1 Unintentional
#5
CAUSES OF
ges
Ages 15-24
#6
LEADING
Actual causes of death
8 Tobacco
-Diet/activity
-Alcohol/illicit
drug use
-Certain
infections
.-Firearms
Unintentional Injuries
Liver Disease
Pnuemonia,Influenza
Suicide
-Sexua
-Motor
I b h.
.
e avlor
vehicles
13
EPIDEMIOLOGICPROCESS
DEFINE
.ndition
.Determine the natural history of the
THE
DITIO
disease
.Identify strategic points of control
.Design control strategies
.Implement control strategies
N
.Define
the health condition
requiring
intervention
.Evaluate control strategies
The Natural History of the
at rat History
the
.A
descri
of
Condition
Condition
.Preexposure-factors
p tion
of
the
..to
problem
.Preclinical-Exposure
events
that
precede
condition
and occur
...Resolution-Return
urlng
ItS courSe
d
Identifying Points of
Control
.Primary
.Secondary
.Tertiary
Prevention
Prevention
a
present leadin!1
development
to
causative
agents, no symptoms present
.Clinical-Symptoms present
to health or
chronic state or death
Designing,
Implementing
Evaluating
and
Strategies
Prevention
14
EPIDEMIOLOGIC
ODELS
HOST
-The host is the
client system
-Triad
*Host
* Agent
affected
by the
particular
condition.
*Environment
Factors that Influence the Host's
Exposure,
AGENT
Susceptibility and
se to an Agent
.Intrinsicfactors
*age
*gender
.The
of
.Physical factors
.Psychological factors
.Presence or absence of immunity
primary
a
cause
health-
related
condition
.Behaviors
AGENTS
.Physical
agents-heat,
trauma,
genetic change
.Chemical agents-medications, poison
N ..ivy
I
V. A V. C
.utrltlve
agents- ron, It , It
.Infectious agents-virus, bacteria
aracteristics
Infectious
-Extent
of
A
gents
of Exposure
.Psychological-stress
15
Characteristic
of
Infectious
Agents
.Infectivity-the
ability of the agent
to invade the host
.Related to the Portal of Entry
.Portal of Exit
.The Portals of Entry and Exit
influence the
.MODE of TRANSMISSION
MODES OF
TRANSMISSION
.direct transmission
.water
.milk
.food
.animal vectors
.fomites
.air
.soil
Characteristic
of
Infectious Agents
.at ogenlcity-the ab.ility of
the agent to cause disease
.Pathogenicity relates to the
Attack Rate
.Attack rate is the proportion
of those exposed to the agent
who develop the disease
Characteristics
of
Noninfectiousagents
."Extent
of exposure"
."Infectivity"
."Virulence"
."Delay between exposure and
disease"
cteristics
of
Infectious
Agents
..
.Vlrulence-the
severity
of the health
problerr\
caused by the agent
ENVIRONMENT
.Physical
.Biological
5
.ocla
. I
16
-
-
0
f C
ausa
"
IS anot
h
t
"
Ion
Dever's Epidemiological Model
(3rd Epidemiologic Model)
.Human Biological factors
er
.*genetic inheritance
Epidemiologic
.*functioning
.*maturation
Model
of physiologic systems
and aging
.Environmentalfactors
.Lifestyle factors
.Health Care System factors
ENVIRONMENTAL
Human Reservoirs
.Physical
* R eservolr-were .
h
th
.Case-actually
has
t
diseasE~
e
microbe exists and
multiplies
*Intermediary-transmits,
.Carrier-harbors
the agent without
having symptoms
i. e., vectors, fomites
TYPES of CARRIERS
T
es of Epidemiologic
.INCUBATIONARY-in
the process of
developing the disease
.CONVALESCENT -symptoms have
subsided
.CHRONIC- a convalescent carrier that
continues to harbor the disease
.TRANSIENT-may
have a subclinical
case, never develop symptoms
Studies
.Descriptive
.Analytic
17
~;;~~~
Descriptive Epidemiology
.-
ANALYTIC
EMIOLOGY
.The
study ofofthe
distribution
a given health
state in a specified
populations in terms of
person, place, time
Analytic Epidemiology
8 Hypothesis-generating
studies
8 Hypothesis-testing
studies
8 The s~ud~ of factors
contributing
to health
states for the purpose of
identifying
causal factors
Hypothesis
generating
studies
.Suggest relationships
between factors
health states
and
.Do not establish causality
Hypothesis.Testing
Types
.Examine
re~~:::s between
the health state and the
supposedcause within
individualsto establish cause
and effect.
of
ypothesis
Testing
Studies
.
.Observatlonal
E
.
.xperlmen t aI
18
Communicable
Disease
COMMUNICABLE
DISEASE
.Diseases spread by direct
contact with an infectious
agent
Chain of Infection
.Infected person or source
.reservoir
.agent
.mode of transmission
.portal of entry and exit
.susceptible new host
Modes of
..
Transmission
.The means by which the
infectious agent is transferred
from an infected person to an
uninfected one
Modes of Transmission
include:
.airborne
.fecal-oral
.direct contact
.sexual contact
.direct innoculation
I bo
.IDsect or anima Ite
.inanimate objectsor soil
0
0
(
Airborne
.Hantavirus
.Chickenpox
.Streptococcal throat infection
.TB
.uenza
Inn
.Meningococcal meningitis
.Pneumococcal pneumonia
1
Fecal-oral
.HepatitisA
.Salmonellaor Shigelladiarrhea
Direct
8Hepatitis
Inoculation
Band
C
.Cryptosporidium
.Ascarisis
8HIY
.E-coli
.Cholera
.Thyphoid
Direct Contact
Insect or Animal Bite
.Malaria
.Scabies
.Rabies
.Lice
.Lyme disease
.Impetigo
.Mononucleosis
.Rocky Mountain Spotted
Fever
.Plague
Portals of Entry and Exit
Portalsof EntryandExit
.The portals through
which the infectious
agent causing the
disease enters and leaves
an infected host.
2
--
Incubation
Period
PRODROMAL
PERIOD
.The period from exposure
to an infectious organism to
development of the
symptoms of the disease.
.The period between
the first symptoms
and the appearance of
the symptoms that
typify
the disease.
Preventing the Spread of
Disease
Co mm
unica
Disease
b Ie
Control
.Control the infectious agent
.Eradic~te.the vehicle of
transmission
.Quarantine infected
individuals
.
Increase Host
Resistance
.Promote
~ --:: .Produce
",,)
c~):
~
general healt
..communicable
Immunity
.Prevent
complications
f
.
0 communlca bl e
disease
.
Other Control Measures
.Legislationrequiringscreening
for
specific
diseases
in high-riskgroups
.Mandatoryreportingofcases
of
disease
.Compulsory
ImmunIZation
prIort 0
school
entry
.Compulsory
examofcontacts
and
treatmen
t
.Re lationofvehicles
oftransmissin
3
Community Health
Nursing Measures
.Contactnotification
.Chemoprophylaxis.
.Education
ENVIRONMENTAL
HEAL
TH
Supportive care
.Political activity
.Immunization
.CaseFinding
.Referral
.Treatment
ENVIRONMENTAL HEALTH
.One of the earliestpublic health
concerns
B ..
f
anized
.egmnmgs 0 org
actiVIties ill
the U.S. started with the Shattuck
report in 1850.
.*disinfection&fumigation
.*pest & vector~ontrol
Federal Government&
Environmental
Health
E
.
I
.Baets natlona
t I h aIth
enVlronmen a e
legislation
.
.Early sanitationactivities included:
d.
* fi
.sa
eguar mg water supplies
*proper sewage,refuse & waste disposal
.*food and milk sanitation
during epidemic
Federal Agencies Involved in
Environmental Health
.EPA-mission to control and
abate pollution
.FEMA-emergency planning,
preparedness &
response
4
--
State
Health
Agencies
Local
Health
Departments
.
Environmental
.Collect information on
environmental pollution
.Maintain environmental disease
registry
.Take part in environmental
monitoring activities
.Provide consultation to LHD
Often responsible for
and
Health
.Prevent, eliminate and control
environmental hazards through
various environmental
programs
ECOLOGICAL
ISSUES
.*implementiug vettor tontrol measnres
.*testiug tommunity waterand air
.*overseeing solid &hazardouswaste
.Deforestation, desertification, loss of
biodiversity
.Global warming
disposal
.*perfonning
.Ozone depletion
.Planetary toxification
food & restaurant
inspettions
.*ensuring sanitationof publit pools
.* ensuringsafehousing
Physical Hazards
.Radiation
.Lead and heavy metals
.Noise
.Overpopulation
Biological Agents
.;0-*
.Infectious
.Insects
agents
and animals
.Plants
5