Introduction to Epidemiology 1. Define epidemiology 2. Describe the history of epidemiology 3. Describe aims and components of epidemiology 4. Discuss on the uses of epidemiology

1. Dr. Swe Swe Latt
Lecturer
Community Medicine Department
International Islamic University Malaysia (IIUM)
Introduction
to Epidemiology

3. Learning outcomes
1. Define epidemiology
2. Describe the history of epidemiology
3. Describe aims and components of
epidemiology
4. Discuss on the uses of epidemiology

4. DEFINITION
The word “epidemiology “ is derived from the
Greek words;
• Epi = among
• Demos = people
• Logos = Study

5. DEFINITION
• “That branch of medical science which treats
epidemics" (Parkin, 1873)
• “The science of the mass phenomena of infectious
diseases”. (Frost, 1927)
• “The study of disease, any disease, as a mass
phenomenon.” (Greenwood, 1934)
• “The study of the distribution & determinants
of disease frequency in man”(Mac Mohan,1960)

6. (John M Last,1988)***
• “The study of the distribution &
determinants of health related states or
events in specified populations, and the
application of this study to the prevention
and control of health problems”.

7. Definition of Epidemiology
Term Explanation
Study includes: surveillance, observation, hypothesis testing,
analytic research and experiments.
Distribution Refers to analysis of: times, persons, places and classes of
people affected.
Determinants Include factors that influence health: biological, chemical,
physical, social, cultural, economic, genetic and behavioral.
Health-related
states and
events
Refer to: diseases, causes of death, behaviours such as use
to 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.

8. COMPONENTS OF
EPIDEMIOLOGY

9. Three components
1. Study of disease frequency –
Measurement of morbidity, disability, mortality
etc (Prevalence rate, Incidence rate, death
rates)
2. Study of distribution of disease – Time,
Place, Person (Descriptive epidemiology)
3. Study of determinants of disease -(Agent,
Host, Environment) – underlying causes?
Analytic epidemiology – Using epidemiologic
methods

10. AIMS OF EPIDEMIOLOGY

11. INTERNATIONAL EPIDEMIOLOGICAL
ASSOCIATION (IEA)
• To describe the distribution & magnitude of
health & disease problems in human
populations.
• To identify etiological factors (Risk Factors)in
the pathogenesis of disease
• To provide the data essential to the planning,
implementation & evaluation of services for the
prevention, control & treatment of disease & to
the setting up of priorities among those
services.

12. THE ULTIMATE AIM
• To eliminate or reduce the health
problem or it’s consequences.
• To promote the health & well being of
society as a whole.

13. Changing patterns of community
Health Problems

14. Uses of Epidemiology
“a means of learning, or asking questions…..
And getting answers that lead to further
questions” (Epidemiology)

15. Uses of Epidemiology *** ( Morris)
1.To study historically the rise and fall of disease
in the population
• Study of h/o of d/s in human population
• Health and d/s pattern – never constant and
changing over short or long period of time
• Old diseases eg. Small pox are conquered,
• New ones (AIDS, Legionnaires’)-identified

16. 2. Community diagnosis
• Identification and quantification of health
problems in community (mortality, morbidity
rates and ratios)
• Defining the need of health care in community
• Benchmark for the evaluation of health services
in community
• Source of new knowledge about d/s distribution,
causation and prevention

17. 3. Planning and evaluation
• Planning is essential for allocation of limited resources
• In developing countries, too many hospitals without knowledge of
particular d/s problems
• Planning facilities for medical care ( no of hospitals, health
manpower)
• Planning facilities for preventive services ( Immunization campaigns,
sanitary services, research)
Evaluation
• Evaluation of control method – hepatitis vaccine and its
effectiveness (cost of large scale application, trained personnel,
storage, transport and etc)
• Prolonged hospitalization of MI patients
•

18. 4.To evaluate the individual’s risks & chances
• Make statement about degree of risk in a
population
• Risk of assessment of smokers and non-
smokers for selected causes of death
(Ca, CHD)

19. 5. To define & refine syndromes
6.To determine the natural history of disease
7. Searching for causes and risk factors

20. Others:
• To investigate the modes of transmission of a
new disease
• To determine the preventable causes of disease
or injury
• To study the biologic spectrum of disease
• To improve the diagnosis, treatment and
prognosis of clinical diseases
• To improve health services and research
• To provide expert testimony in courts of law

21. History
of
Epidemiology

22. HIPPOCRATES (460-377 B.C.)
“On Airs, Waters, and Places”
–Hypothesized that disease
might be associated with the
physical environment, including
seasonal variation in illness.
 Idea that disease might be
associated with physical
environment

23. JOHN GRAUNT (1662):
“Nature and Political
Observations Made Upon the
Bills of Mortality”
– First to employ quantitative
methods in describing
population vital statistics.

24. Thomas Sydenham (1624-1689)
Recognized as a founder
of clinical medicine and
epidemiology
Emphasized detailed
observations of patients &
accurate recordkeeping

25. James Lind (1700’s)
 Designed first experiments to
use a concurrently treated
control group

26. Edward Jenner (1749-1823)
 Pioneered clinical trials for
vaccination to control spread of
smallpox
 Jenner's work influenced many
others, including Louis Pasteur
who developed vaccines against
rabies and other infectious
diseases

27. Ignas Semmelweis (1840’s)
 Pioneered handwashing
to help prevent the spread
of septic infections in
mothers following birth
 Childbed fever (puerperal
fever)

28. John Snow (1813-1858)
Father of epidemiology
Careful mapping of cholera cases
in East London during cholera
epidemic of 1854
Traced source to a single well on Broad Street
that had been contaminated by sewage
Formulated natural epidemiological
experiment to test the hypothesis that cholera
was transmitted by contaminated water.

29. Epidemiological observation through
a natural experiment can suggest the
etiology and some method of the
prevention.

30. Epidemiological observation through a natural
experiment can suggest the etiology and some method
of the prevention.

31. DOLL & HILL (1950)
Used a case-control design to describe and
test the association between smoking and
lung cancer.

32. FRANCES at al. (1950)
Huge formal field trial of the Poliomyelitis
vaccine in school children.

33. DAWBER et al. (1955)
Used the cohort design to study risk factors
for cardiovascular disease in the
Framingham Heart Study.

34. History of Epidemiology
(Cont’d)
• Vital Statistics
– John Graunt (1620-1674)
– William Farr (1807-1883)
• Occupational medicine
& Industrial Hygiene
– Bernardino Ramazzini (1633-1714)
• Role of carriers in transmission
– Typhoid Mary & George Soper

35. Typhoid Mary & George Soper
 Mary Mallon, a cook responsible for most famous outbreaks of
carrier-borne disease in medical history
 Recognized as carrier during 1904 N.Y. typhoid fever epidemic
 When source of disease was traced, Mary had disappeared only to
resurface in 1907 when more cases occurred
 Again Mary fled, but authorities led by George Soper, caught her and
had her quarantined on an island
 In 1910 the health department released her on condition that she
never accept employment involving the handling of food
 Four years later, Soper began looking for Mary again when two new
epidemics broke out; Mary had worked as a cook at both places
 She was found and returned to North Brother Island,
where she remained the rest of her life until a
paralytic stroke in 1932 led to her slow death,
six years later

37. U.S. History of Epidemiology
• Lemuel Shattuck (1850)
– Proposed creation of a permanent statewide public
health infrastructure
– Recommended establishing state & local health offices to
gather statistical information on public health conditions

38. • Quarantine Commissions (1857)
• 1st Public Health Book (1879)
• U.S. Public Health Service founded (1902)
• Pure Food and Drug Act (1906)
• Pasteurization of milk (1913)
• 1st School of Public Health (1913)

39. Historic Aspects of the
Development of Morbidity
Statistics in the U.S.
• Edgar Sydenstricker (Early 1900’s)
– Pioneer public health statistician
• Three notable studies:
– Tuskegee syphilis study (1932-1970)
– Framingham heart study (1948-present)
– Epidemiology of cigarette smoking (1950’s
- present)

40. Wake-up Calls
• AIDS recognized
• Cholera in the southern hemisphere
• Legionnaire’s disease
• New forms of hepatitis
• Chlamydia and heart disease
• Hospital acquired infections
• Antibiotic resistance

41. Future Challenges
• Instant global transmission of pathogens
– Population overcrowding
– Ease of travel
– Importation of foods

42. QUIZ BONUS
Epidemiology is
A. Branch of medical science which treats
epidemics
B. Science of the mass phenomenon of infectious
diseases
C. Study of disease, any disease, as a mass
phenomenon
D. Study of distribution and determinants of
disease frequency in masses
E. All of the above
Answer (e)

43. QUIZ BONUS
Study of time, place and person distribution of
health related events is known as:
A. Descriptive epidemiology
B. Experimental epidemiology
C. Analytical epidemiology
D. Clinical epidemiology
Answer (a)

44. QUIZ
True about activities in epidemiology.
A. Measures population health.
B. Ensure compliance to antibiotics.
C. Monitor incidence of infectious
diseases.
D. Advocate evidence based policy
making.
E. Phase I clinical trial.
A. TRUE
B. FALSE
C. TRUE
D. TRUE
E. FALSE
(JAR)

45. References
• Park K
• Leon Gordis
• AH Suryakantha (Community Medicine
with recent Advances)