THIS IS AN INTRODUCTION TO EPIDEMIOLOGY, PREPARED BY ABDIFITAH SALAD TARABI THIS BREIF SLIDE CAN HELP U TO UNDERSTAND THE FULL MEANING OF THIS COURSE UNIT. AND I WILL PUBLISH ANOTHER LECTURES SOON.

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Somalia 31/10/017

3. Epidemiology
The word epidemiology comes from the Greek words
Epi, meaning on or upon, demos, meaning people,
and logos, meaning the study of.
Study of the distribution and determinants of
health related states or events in specified
populations and the application of this study to
control health problems.
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4. Cont....
The concept behind "epidemiology" is that,
disease or illness or ill health is not randomly
distributed in human populations. Rather, each of us
has certain characteristics that predispose us to, or
protect us against a variety of diseases. These
characteristics may be genetic or may be the result of
exposure to certain environmental hazards.
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5. Some important terms in the definition
 Originally, epidemiology , as the name says, was meant understanding
the epidemics but now the term is much broader than epidemics, it deals
with all health-related events such as:
 Endemic communicable diseases and non-communicable diseases.
 Additional epidemiologic expansion had been developed and applied to
chronic diseases, injuries, birth defects, maternal-child health,
occupational health, and environmental health.
 behaviors related to health and well-being, such as amount of exercise and
seat belt use
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6. Specified populations
 Although epidemiologists and direct health-care providers (clinicians) are
both concerned with occurrence and control of disease, they differ greatly
in how they view the patient.
 The clinician is concerned about the health of an individual;
 The epidemiologist is concerned about the collective health of the
population.
In other words
 The clinician’s patient is the individual;
 The epidemiologist’s patient is the community.
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7. Determinants
Determinant: any factor, whether event,
characteristic, or other definable entity, that brings
about a change in a health condition. Epidemiology
is used to search for determinants, which are the
causes and other factors that influence the
occurrence of disease and other health-related
events.
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8. Distribution
Epidemiology is concerned with the frequency and
pattern of health events in a population:
Frequency refers not only to the number of health
events such as the number of cases of meningitis or
diabetes in a population, but also to the relationship
of that number to the size of the population
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9. Cont..
Pattern refers to the occurrence of health-related events by time, place, and
person.
 Time patterns: may be annual, seasonal, weekly, daily, hourly, or any
other breakdown of time that may influence disease or injury occurrence.
 Place patterns: include geographic variation, urban/rural, and location
of work sites or schools.
 Personal characteristics: such as age, sex, marital status, and
socioeconomic status, as well as behaviors and environmental exposures.
Characterizing health events by time, place, and person are activities of
descriptive epidemiology.
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10. Three major questions are usually asked in
this discipline of epidemiology:
What is the distribution of the disease in terms of person? "who"
 Means, who is getting the disease? Most diseases attack certain
people more than others. Many infectious diseases (measles,
diarrheoa) affect children more than adults. Road traffic accidents
affect drivers more than others. STDs affect young adults who are
sexually active than adults. Many chronic, degenerative diseases
(cancer, diabets) affect late adulthood more than other age groups
(early and middle aged groups).
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11. Cont...
What is the distribution of the disease in terms of place? "where”
 Means, where cases are occurring? A very useful way to show
where cases are occurring is to use a spot-map. For instance,
using a map of the district, cases of the diseases are marked
with a colored dot, showing where each lived at the time of
onset of the disease.
 You can then see where the cases are close together
(sometimes called clusters). Of course, you must take into
account where people lived too.
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12. Cont...
What is the distribution of the disease in terms of time? "when"
Time trends are perhaps the most important patterns
to follow in surveillance because they tell you which
health problems are increasing and need to be
controlled and whether a community health
programme (e.g., an immunization programme) is
successful in reducing the incidence of a disease.
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13. Objectives and uses of epidemiology
 To identify etiology or cause of a disease and the relevant risk factors:
 To determine the extent and burden of disease in community:
 To study the natural history of the disease:
 Evaluate both existing and newly developed preventive and therapeutic
measures:
 To develop health policy for addressing health problems:
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