Introduction to Epidemiology and Dynamics of Disease Transmission By the end of the presentation, one would be able to: Define Epidemiology Describe 5 main objectives of Epidemiology Define disease and its types Describe different modes of Transmission of Infection Demonstrate understanding of Herd Immunity Describe Important periods related to infection and disease Differentiate between sporadic, endemic, epidemic and pandemic

1. Introduction to Epidemiology
&
Dynamics of Disease Transmission
DR. SANA MURTAZA
COMMUNITY MEDICINE

2. Learning Objectives
By the end of the session, student should be able to:
Define Epidemiology
Describe 5 main objectives of Epidemiology
Define disease and its types
Describe different modes of Transmission of Infection
Demonstrate understanding of Herd Immunity
Describe Important periods related to infection and disease
Differentiate between sporadic, endemic, epidemic and
pandemic

3. Epidemiology
“Study of frequency, distribution (time, place, person) and
determinants of health related states or events in specified
population and the application of this study to control of
health problems”

4. Objectives of Epidemiology
1.To determine the extent of disease in a community (one out of
10 individuals have hepatitis)
2.Study the natural history of disease and prognosis of disease
(Low immunity predisposes to early death from Tuberculosis)
3.Identify the cause of a disease and relevant risk factor (stress
and Heart Disease)
4.To evaluate existing and newly developed preventive and
therapeutic measures & modes of healthcare delivery
(pneumococcal vaccine decreases the prevalence of pneumonia)
5.Provide the foundation for developing public policy relating to
environmental and genetic issues (high levels of pollution and
health problems)

5. Epidemiologic Achievement: 3 Examples
Edward Jener and Smallpox
Edward Jenner was born in 1749 and became very interested in the problem of
smallpox
He observed that young women whose occupation was milking the cows
developed a mild disease called cowpox
Later, during smallpox outbreaks, the disease appeared not to develop in these
young women
Jenner became convinced that cowpox would be a protection against smallpox
He removed some cowpox material from hand of a dairy maid and
administered by Jenner to an 8-year-old "volunteer"
He later exposed the child to smallpox 6 weeks later
The child did not contract the disease
The results of the first vaccination and of what followed were the saving of
literally millions of human beings throughout the world

6. Types of Diseases

7. Chain of Infection & Modes of
Transmission of Communicable Disease

8. Herd Immunity

9. Important Terms related to
Infection and Disease
Incubation Period
Infection Appearance of signs and symptoms
Guides on the length of Quarantine (Strict enforced Isolation)
Timely provision of chemoprophylaxis to the patients
Helps in decision making for Screening
Period of Communicability
Individual suffering can transfer it to others
Guides on Duration of Isolation of the infected patient
Latent period
Infection Beginning of transmission
Guides on period of safety
Window period
Infection Appearance of antibodies
An affected individual may transmit infection which can’t be detected

10. Levels of disease
occurrence

11. Disease Occurrence in
Population

13. Outbreak- Definition
Sudden occurrence of an epidemic in a relatively
limited geographic area. While an outbreak is usually
limited to a small focal area, an epidemic covers larger
geographical areas & has more than one focal point.

14. Thank you