Dr. Swe Swe LattLecturer

Community Medicine Department International Islamic University Malaysia (IIUM)

Introduction to Epidemiology

Learning outcomes

1. Define epidemiology2. Describe the history of epidemiology

3. Describe aims and components of

epidemiology 4. Discuss on the uses of

epidemiology

DEFINITION

The word “epidemiology “ is derived from the Greek words;

• Epi = among• Demos = people• Logos = Study

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)

(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”.

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.

COMPONENTS OF EPIDEMIOLOGY

Three components1. 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

AIMS OF EPIDEMIOLOGY

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.

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.

Changing patterns of community Health Problems

Uses of Epidemiology “a means of learning, or asking

questions….. And getting answers that lead to further questions” (Epidemiology)

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

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

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•

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)

5. To define & refine syndromes

6.To determine the natural history of disease

7. Searching for causes and risk factors

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

History of

Epidemiology

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

JOHN GRAUNT (1662):

“Nature and Political Observations Made Upon the Bills of Mortality”

– First to employ quantitative methods in describing population vital statistics.

Thomas Sydenham (1624-1689)

Recognized as a founder of clinical medicine and epidemiology

Emphasized detailed observations of patients & accurate recordkeeping

James Lind (1700’s)

Designed first experiments to use a concurrently treated control group

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

Ignas Semmelweis (1840’s)

Pioneered handwashing to help prevent the spread of septic infections in mothers following birth

Childbed fever (puerperal fever) 

John Snow (1813-1858)

Father of epidemiologyCareful mapping of cholera cases in East London during cholera epidemic of 1854Traced source to a single well on Broad Street that had been contaminated by sewageFormulated natural epidemiological experiment to test the hypothesis that cholera was transmitted by contaminated water.

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

Epidemiological observation through a natural experiment can suggest the etiology and some

method of the prevention.

DOLL & HILL (1950)Used a case-control design to describe and

test the association between smoking and lung cancer.

FRANCES at al. (1950)

Huge formal field trial of the Poliomyelitis vaccine in school children.

DAWBER et al. (1955)Used the cohort design to study risk factors

for cardiovascular disease in the Framingham Heart Study.

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

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

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

• 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)

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)

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

Future Challenges• Instant global transmission of

pathogens– Population overcrowding– Ease of travel– Importation of foods

QUIZ BONUS Epidemiology is A. Branch of medical science which treats

epidemicsB. Science of the mass phenomenon of

infectious diseasesC. 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)

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)

QUIZTrue 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.TRUEB.FALSEC.TRUE

D.TRUE

E.FALSE (JAR)

References • Park K • Leon Gordis• AH Suryakantha (Community

Medicine with recent Advances)