Community Dentistry Department HBS Medical and Dental College, Islamabad

1. Introduction to Epidemiology
Block-5, Module-9
Dr Qurat-Ul-Ain
Assistant Professor/ HoD Community Dentistry Department

2. Learning Objectives
 - Definition of epidemiology
 - Purpose & use of epidemiology
 - 5Ws of epidemiology
 - Categories of epidemiology
 - Levels of disease occurrence

3. Definition Of Epidemiology
Epidemiology is the study of the distribution and
determinants of health-related states or events in
specified populations, and the application of this
study to control of health problems (Johon M
Last, 1998)

4. Purpose Of Epidemiology
 Assessing the community’s
health
 Identify new and emerging
diseases
 Monitor and track existing
diseases
 Evaluate the effectiveness of
control measures

5. Uses For Epidemiology
Health status & health services
 1. study history of the health
population
 2.determine the health of the
community
 3.Measure the effectiveness of health
services
Disease etiology= causation
 1. estimate the individual risks &
chances
 2.Identify syndromes
 3. search for causes

6. The Five Ws of Epi= Principals of Epidemiology
 1-What=Clinical
 2-Who=Person Descriptive Epidemiology(Distribution)
 3-Where=Place
 4-When=Time
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 5-Why / How= Cause, risk factors, modes of transmission
Analytic Epidemiology(Determinants)

9. Categories of epidemiology
1.Descriptive
2.Analytic

10. Categories of epidemiology
 Descriptive Studies: Overview
1. Display patterns of occurrence
2. Focus on person, place, time
3. Useful if little is known
•Used for
•Program planning
•Generating hypotheses

11. Categories Of Epidemiology
 Analytic Studies, Overview
1. Analytic studies used in research are frequently larger and more
complex than descriptive studies
2. Assess determinants of diseases
3. Focus on risk factors and causes
4. Analyze distribution of exposures and diseases
5. Key feature: use comparison groups
6. Used to:
•Test hypotheses
•Look for and measure associations

12. Levels Of Disease Occurrence
 In the study of epidemiology, disease is further classified based on
how many people it affects and whether or not the disease
represents a new outbreak or maintains a constant and stable
presence in a geographic location.
 The following terms are used to classify disease:
1. Endemic,
2. Epidemic,
3. Sporadic
4. Pandemic

13. Endemic
 Endemic disease refers to the presence of a
particular disease or pathogen that exists
permanently and at a constant level in a population
of people located in a specific geographic location.
 For example, in certain parts of Africa, malaria
(caused by the Plasmodium protozoan species) is a
constant concern.

14. Epidemic
 Epidemic disease is a disease outbreak that
occurs as a larger-than-expected number of cases
occurring over a short time in a geographic
region.
 Influenza (flu) is a good example of an epidemic
disease.
Influenza can be caused by many strains of influenza viruses. It
is a contagious respiratory illness that can lead to severe
complications, including death in high-risk populations such as
children, the elderly, or immunocompromised patients.

15. Sporadic
 Sporadic disease is a disease that occurs only
occasionally or in scattered incidents.
 Typhoid fever, also called enteric fever, is an
example of a sporadic disease.
Typhoid fever is caused by the bacterium Salmonella typhi and is
life threatening

16. Pandemic
 A pandemic disease is disease outbreak affecting a large
percentage of the world’s population over a vast (even
worldwide) geographic region or regions.
 A historical example of pandemic disease includes the Black
Death, also known as Black Plague
 Current example: Corona Virus (COVID-19)