Nursing 205

Introduction to Epidemiology

Epidemiology the Basic Epidemiology the Basic Science of Public HealthScience of Public Health

Imagine that you are a detective and a theft has been committed… a mysterious theft has been committed

You examine all the clues and investigate all the suspects…

Using the investigative tools of your trade…

You solve the Mystery

Disease Detectives=Epidemiologists

Epidemiology- Study of distribution and the determinants of disease in a population

Link between smoking and Link between smoking and lung cancerlung cancer

Sugary drinks increase risk Sugary drinks increase risk of diabetes…of diabetes…

N.S. tick numbers could be rising, says N.B. N.S. tick numbers could be rising, says N.B. scientist scientist

Up until 2011, there have been 120 cases of Up until 2011, there have been 120 cases of Lyme disease confirmed in the provinceLyme disease confirmed in the province: :

Wednesday Sept 5Wednesday Sept 5

Halifax eatery gets OK to reopen following Halifax eatery gets OK to reopen following illness outbreakillness outbreak

Dozens of suspected norovirus cases were Dozens of suspected norovirus cases were linked to the waterfront eatery linked to the waterfront eatery

New norovirus cases prompt food services closure at resort Resort rep says two weddings were to be held at the resort

this weekend

The Epidemiologic World of Discovery is now in your hands…..

Clinical medicine and epidemiology differ with respect to which major aspect?

A. Practice focus

B. Health monitoring

C. Determinants of disease

D. Evaluation of interventions

Practice

focu

s

Health m

onitorin

g

Determ

inants of d

isease

Evaluation of in

terventions

0% 0%0%0%

30

Nurses in community health often use epidemiology because in the community, it is often difficult to control the environment. Which of the following statements demonstrates an epidemiological strategy

for monitoring disease trends?

A. A community health nurse (CHN) conducts a diabetic education class for newly diagnosed clients.

B. A CHN investigates reported cases of whooping cough in an elementary school.

C. A CHN organizes a health and wellness fair at the community health centre.

D. A CHN participates on a county school board that addresses student health issues.

A community

health nur..

A CHN inve

stigate

s repor..

.

A CHN organizes a

health...

A CHN particip

ates on a ...

0% 0%0%0%

30

Definition

Epidemiology is defined as the study of the distribution and determinants of health-related states or events in specified populations (Last, 2001)

Study

It refers to the use of tested and validated methods of scientific inquiry. These include surveillance, observation, hypothesis testing, analytic research and experiments….

Distribution Refers to the frequency and pattern of health events in a

population (age, sex, occupation, ethnicity etc) It tells about the who, when and where of health events and

the characteristics of those affected

Determinants

All the physical, biological, social, cultural and behavioral factors that influence health

TypesTypes

Descriptive epidemiologyDiscusses disease/event/condition in terms of person, place and time

Who, where and when

Analytical epidemiologyLooks at origins or causes of the disease, and deals with determinants of health (factors, exposures, behaviors, characteristics that influence patterns)

Analytic epidemiology differs from descriptive epidemiology in its search for

which one of the following?

A. The when of disease patterns

B. The where of disease patterns

C. The why of disease patterns

D. The who of disease patterns

The when of d

isease

patt...

The where

of dise

ase pat..

.

The why o

f dise

ase pattern

s

The who of d

isease

patterns

0% 0%0%0%

30

Focuses on populations Population/community from which a certain

condition originates Identifies DOH and disease in communities Investigates and evaluates interventions to

prevent disease and maintain health

Application- How do we use Epidemiology?

Is health improving or declining? What actual and potential health problems are there? Evaluating Health Services

– Efficacy - Can it work in an ideal setting?– Effectiveness - Does it work in the "real"

world? - Efficiency - How can the service utilize its resources

for maximum benefit?

What was Epidemiology then?

History Contributed to understanding, preventing

and controlling epidemics of communicable diseases such as the plague and cholera

https://www.youtube.com/watch?v=hs8wjxW4U4E

What is Epidemiology now? A discipline that focuses on factors that affect

the health and illness of a given population

Cornerstone of public health and preventative medicine (e.g. communicable/non-communicable diseases, occupational health, environmental health, health services, deaths, accidents, birth defects, child health, health behaviors, parental health

Disease Transmission

Host

EnvironmentInfectio

us agent

Epidemiological Triangle

Chain of TransmissionChain of Transmission

Agent, host, and environment alone are not sufficient to cause an epidemic.

Requires a source for the agent, a portal of exit, a mode of transmission, and a portal of entry.

Camplyobacter bacteriaCamplyobacter bacteria

Agent: Camplyobacter bacteria Host: Humans working at a disaster site Environment: A disaster scene at which food brought by

volunteers is served to people working on the disaster. Source for the agent: Chicken that was not properly prepared

or was undercooked, was delivered to the disaster scene and was not held at proper temperature

Mode of transmission: Chicken juices with infective quantities of Campylobacter

Portal of entry: Oral, is a person eats contaminated food and ingests enough bacteria to become “sick”

Vector

Host

EnvironmentAgent

Susceptible

GeneticNutritional

Immunologic

Biologic

Physical

Chemical

Factors that Increase Risk

Host characteristics Agents (examples) Environmental factors

Age, sex, race, religion Biologic (bacteria/viruses, fungi, insects)

Temperature

Customs Chemical (poison, alcohol, smoke) Humidity, altitude

Occupation Physical (trauma, radiation, fire,cold)

Crowding, housing

Genetic profile Nutritional (lack, excess) Neighbourhood

Marital status Water, milk, food

Family background Radiation

Previous diseases Air pollution

Immune status Noise

AgentAgent

1. The amount of agent needed to produce illness

Chickenpox-only small amount of the virus are needed to cause disease

TB- need exposure to large amounts of the tubercule bacilli.

Agent…Agent…

Virulence- strength of the organismInfluenza A symptoms severe and longer than B

Invasiveness-how much it affects the hostGonorrheal usually limited to the genito-urinary tract where syphilis affects many body tissues (brain)

Ability to mutateSome can mutate i.e. penicillin resistant gonorrhea

Generation of Pandemic Generation of Pandemic Influenza: “Antigenic Shift”Influenza: “Antigenic Shift”

36“the mixing vessel”

PandemicPandemic

ClassicalClassical Swine Influenza Swine Influenza Swine=mixing vessel for influenza- human, swine &

avian – influenza in pigs firstrecognized in 1918 pandemic

2009 H1N1 –new lineage

Influenza pandemics occur when a new strain of influenza virus appears that most people have no natural immunity to

cynthiamania.files.wordpress.com

www.ars.usda.gov/2009H1N1/index.html?

pf=1

Modes of Disease Transmission

1. Directa) Person-to-person contact

2. Indirecta) Common vehicleb) Vector

Methods of Disease Methods of Disease TransmissionTransmission

Direct transmission: By coming into direct contact with the infectious lesion or infected body fluids (e.g., blood, saliva, semen, vaginal secretions).

•Indirect transmission: Transfer of organisms to a susceptible person can occur by, for example, handling contaminated instruments or touching contaminated surfaces and then touching the face, eyes, or mouth.

Host-population at riskHost-population at risk

State of immunity-Immunity refers to the host’s ability to resist a particular agent

Genetic susceptibilityImmutable characteristics (age, sex)Life style factors (diet & exercise)

EnvironmentEnvironment

Refers to all external factors surrounding the host that may influence vulnerability or resistance

Physical properties such as water, air, climates and the seasons

Social and economic considerations: Family, community, economic status, housing, customs and mobility.

OUTLINE the EPIDEMIOLOGICAL TRIANGLE for E-coli 0157:H7

Other modelsOther models

The web of causation (complex)Examines all of the factors that interact with each other to produce the health conditionMain component of this model is the idea that the whole is more than a sum of its separate parts…

J Moseley 2013

PHAC (2006) Skills Enhancement for Health Surveillance

Control & PreventionControl & Prevention

Depends on finding the weak link and developing measures to attack, reduce or eliminate the threat

Control: – 1. Preventive activities– 2. Measures to reduce

seriousness of the illness

J Moseley 2013

Control measures reduceControl measures reduce……....

A) severity of illnessB) length of illnessC) cost of treatmentD) short & long term effects of

illnessE) reduce risk of death

J Moseley 2013

Four Levels of PreventionFour Levels of Prevention

Primordial Prevention(new – divides primary into two levels)- aims to stop the establishment of risk

factors, diseases or health-related events

Ex: policy and procedures to stop BSE

entering Canada; anti-tobacco legislation

J Moseley 2013

J Moseley 2013

Secondary Prevention:- aimed at subclinical disease- enables early detection to correct

departure from a state of health

eg: pap test, colorectal screening, PSA, cholestrol screening, blood pressure, fasting glucose

J Moseley 2013

Tertiary Prevention:– directed at the clinical stage of

disease- aim to reduce long-term

impairments eg: physiotherapy after a stroke

J Moseley 2013

Who was historically described as the “father of epidemiology”?

A. Lambeth

B. Lister

C. Koch

D. Snow

Lambeth

Liste

r Koch

Snow

7%

73%

16%

5%

A form of epidemiology that describes a disease according to person, place, and

time is descriptive epidemiology.

A. True

B. False

True

False

27%

73%

Screening programs are an example of primary preventionA. True

B. False

True

False

94%

6%

The complex contributory interrelationship of many factors that interact to affect

disease is which of the following?

A. Epidemiological triangle

B. Preclinical pathogenesis

C. Web of causality

D. Primary prevention

Epidemiological tr

iangle

Preclinica

l path

ogenesis

Web of c

ausalit

y

Primary

prevention

33%

0%

67%

0%

Which one of the following illustrates a host factor?

A. Radiation

B. Crowding

C. Pesticides

D. Diet

Radiation

Crowding

Pesticid

esDiet

6%

67%

6%

20%