EPIDEMIOLOGICAL PERSPECTIVE: DEFINITION OF TERMS AND CONCEPTS, SCOPE AND USES - PowerPoint Presentation

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EPIDEMIOLOGICAL PERSPECTIVE: DEFINITION OF TERMS AND CONCEPTS, SCOPE AND USES

TUNRAYO OLUWADARE

DEPARTMENT OF COMMUNITY MEDICINE

ABUAD

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Introduction

Overview of epidemiology

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Definition of terms and concepts

Epidemiology

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.

WHO

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Definition of terms and concepts contd.

Epidemiology is the

study (scientific, systematic, data-driven)

of the

distribution (frequency, pattern)

and

determinants (causes, risk factors)

of

health-related states and events (not just diseases)

in specified

populations (

patients in

community, individuals viewed collectively),

and the

application of (since epidemiology is a discipline within public health)

this study to the control of health problems.

CDC

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Term

Explanation

Study

Includes : surveillance, observation, hypothesis

testing, analytical research and experiments

Distribution

Refers

to analysis of : time, persons and places

Determinants

Includes: factors that influence health;

biological, chemical, physical, social, cultural, economic,

genetic and

behavioural

.

Health-related states and events

refer to: diseases, causes of death,

behaviours

such as use of tobacco,

positive health states, reactions to preventive regimes and provision and

use of health services.

Specified populations

include those with identifiable characteristics, such as occupational groups.

Application to prevention and control

the aims of public health—to promote, protect, and restore health.

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Definition of terms and concepts contd.

Disease frequency

It is summarizing the occurrence of disease, disabilities, death or health related events in form of rates and ratios

Incidence rate

Prevalence rate

Mortality rate

Morbidity rate

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Definition of terms and concepts contd.

Disease distribution

Epidemiologists examines whether there is an increase or decrease in disease/health related events over time span .

It is in terms of person , place and time (PPT

)

Determinants of disease

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Definition of terms and concepts contd.

Epidemic

It is the

unusual occurrence

in a community or region of disease, specific health related events clearly in

excess

of

expected occurrence

.

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Definition of terms and concepts contd.

Endemic

It refers to the constant presence of a disease or infectious agent within a given geographical area or population group, without importation from outside.

It may also refer to the usual or expected frequency of disease within such area or population group.

Hyperendemic

It expresses that the disease is continually present at a high incidence and/or prevalence rate and affects all age group equally.

Holoendemic

It is a high level of infection beginning early in life and affecting most of the child population.

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Questions

A sporadic disease can become epidemic under

favourable

conditions

An endemic disease under

favourable

conditions can become

Holoendemic

Epidemic

Endemic

Hyperendemic

What form of endemic is Malaria

Endemic

Hyperendemic

Epidemic

Holoendemic

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Definition of terms and concepts contd.

Pandemic

It is an epidemic affecting a large proportion of the population , occurring over a wide geographical area such as a section of a nation, the entire nation, a continent or the world.

Eg

influenza

pandemic, COVID-19 pandemic

Sporadic

This is when cases occur irregularly , haphazardly from time to time.

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Definition of terms and concepts contd.

Zoonoses

It is an infection or disease that is transmissible under natural conditions from animals to man, it may be enzootic or epizootic.

Forms of zoonosis

Antropozoonosis

: infection transmitted to man from vertebrate animals

eg

. , rabies, plague ,

antrax

etc.

Zooantroponosis

: infections from man to vertebrate animals e.g., human tuberculosis in cattle

Amphixenosis

: infections maintained in both man and lower vertebrates that may be transmitted in either direction e.g.,

T.cruzi

, S.

japonicum

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Definition of terms and concepts contd.

Host

Is a person or animal , including arthropods and birds that

affords subsistence or lodgement to an infectious

agent under

natural

conditions

.

obligate

host

means the only host, e.g., man in measles

and typhoid

fever.

Definitive/Primary

hosts

are those

in which the parasite attains maturity

or passes

its sexual

stage.

Secondary/Intermediate

hosts are those in which

the parasite is in a larval or asexual state

A

transport

host

is a

carrier in

which the organism remains alive but does not

undergo development.

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Definition of terms and concepts contd.

Exotic

These are diseases that are imported into a country in which they do not otherwise occur.

Contagious disease

A disease that is transmitted through

contact

Communicable diseases

Are diseases due

to a specific infectious agent

capable

of being directly or indirectly

transmitted from

man to man, animal to animal, or from

the environment to

man

or animal

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Definition of terms and concepts contd.

Contamination

The presence of an infectious agent on a body

surface, also

on or in clothes, beddings, toys, surgical instruments

or dressings

, or other inanimate articles or substances

including water

, milk and

food.

Infestation

It is the

lodgement, development

and reproduction

of arthropods on the surface of the body or

in the

clothing, e.g., lice, itch

mite.

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Definition of terms and concepts contd.

Infection

The entry and development or multiplication of

an infectious

agent in the body of man or

animals.

An infection does not always cause illness

.

subclinical

or

inapparent

infection

(

e.g

.,

polio)

latent

infection (

e.g

.,

virus

of

herpes simplex

)

manifest

or

clinical infection.

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Definition of terms and concepts contd.

Surveillance

Is the continuous scrutiny

of the factors that determine the occurrence

and distribution

of disease and other conditions of

ill health.

Nosocomial infection/hospital acquired

It is an infection originating

in a patient while in a hospital or other

health care

facility.

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Definition of terms and concepts contd.

Eradication

Termination of all transmission of infection

by extermination

of the infectious agent through

surveillance and

containment

.

Eradication

is an absolute process,

an "all

or none" phenomenon, restricted to termination of

an infection

from the whole world.

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Definition of terms and concepts contd.

Cases

Is defined as

a

person in the population or study group identified as having the particular disease, health disorder or condition under

investigation.

Carrier

Is

defined

as an

infected person or animal that

harbors

a

specific infectious

agent in the absence of discernible clinical

disease and

serves as a potential source of infection for

others.

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Definition of terms and concepts contd.

Opportunistic infection

This is infection by an organism(s) that takes

the opportunity

provided by a defect in host

defence

to

infect the

host and hence cause disease.

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Uses

Assessing community health

Making individual decisions

Completing the clinical picture

Searching for causes

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Uses

Assessing community health

D

escriptive epidemiology.

What

are the actual and potential health problems in the community?

Where

are they occurring?

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Uses contd.

Assessing community health

Which populations are at increased risk?

Which problems have declined over time?

Which ones are increasing or have the potential to increase?

How do these patterns relate to the level and distribution of public health services available?

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Uses contd.

Making individual

decisions

When

persons decide to quit smoking, climb the stairs rather than wait for an elevator, or use a condom, they may be influenced, consciously or unconsciously, by epidemiologists' assessment of risk.

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Uses contd.

Completing the clinical picture

For

example, in late 1989, a physician saw three patients with unexplained eosinophilia (an increase in the number of a specific type of white blood cell called an eosinophil) and myalgia (severe muscle pains). Although the physician could not make a definitive diagnosis, he notified public health authorities.

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Uses contd.

Completing the clinical picture

More recently, epidemiologists, clinicians, and researchers around the world have collaborated to characterize SARS, a disease caused by a new type of coronavirus that emerged in China in late

2002 and late 2019.

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Uses contd.

Searching causes

Much epidemiologic research is devoted to searching for causal factors that influence one's risk of disease.

Ideally

, the goal is to identify a cause so that appropriate public health action might be taken.

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Uses contd.

Searching causes contd

.

Examples date from the removal of the handle from the Broad St. pump following John Snow's investigation of cholera in the Golden Square area of London in 1854.

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Presentation 1

Discuss extensively the mode of

disease

transmission

Life cycle of Plasmodium