Introduction to Epidemiology

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Introduction to Epidemiology

• Sumattana.g_at_msu.ac.th

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Concept of Epidemiology

• Epidemiology is the study of the occurrence,
  distribution and determinants (which are dynamic)
  of health problems and diseases in human
  populations or communities. The primary unit of
  concern is a group of persons, not any single
  person. Therefore, epidemiology deals with
  population pathology, not clinical pathology
  (disease of a single person), nor microscopic
  pathology (disease of a cell or tissue). All
  population pathology relates back to the
  community as the source of materials for
  investigation and results from epidemiologic
  study study are interpreted in terms of the
  group, not individual.

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Epidemiology for...

• Epidemic disease Past
• Communicable disease
• Non-communicable disease
• Non-infectious disease Present
• Chronic disease
• Occupational disease
• Environmental disease

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EPIDEMIOLOGY

• EPI on, upon
• DEMOS people, population
• LOGOS knowledge, study
• doctrine, discourse
• science

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Evolution of Definition

• The science or doctrine of epidemics
• (New standard Dictionary of English Language)
• The science of infective diseases, their prime
  causes, propagation and prevention
• (Stallybrass)
• The study of conditions known or reasonably
  supposed to influence the prevalence of disease
• (Lumsden)

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Modern Meaning

• Epidemiology is the science which concerns itself
  with the natural history of disease as it is
  expressed in groups of persons related by some
  common factors of age, sex, race, location or
  occupation as distinct from the development of
  disease in an individual (American
  Epidemiological Society)
• Epidemiology is the study of patterns of disease
  and the factors that cause disease in man (CDC)
• Epidemiology is the study of the distribution and
  determinants of disease frequency in man
  (MacMahon Pugh)

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Epidemiology

• Epidemiology is the study of the occurrence,
  distribution, determinants (which are dynamic) of
  health problems and disease in human populations
  or communities

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Aim an Purposes of Epidemiology

• To describe and analyze disease occurrences and
  distribution according to such variables as age,
  race, sex, occupation, temporal frequency of
  occurrence, periodic fluctuation, long term
  trends (time-trend analysis) and geographic
  distribution, in order to make community
  diagnosis and to estimate the morbidity and
  mortality risks.

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Aim an Purposes of Epidemiology

• To carefully analyze the characteristics and
  interactions of agents, host and environmental
  factors in order to search for causes determine
  all details of natural history and preventive and
  control measures and disclose gaps in knowledge.

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Aim an Purposes of Epidemiology

• To improve medical care and provide
  administrative guidance for community health
  services.
• To stimulate the use of systematic approach of
  scientific research to study other problems in
  public health related fields such as dentistry,
  welfare, education, administration and other
  important spheres.

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Scope and Content of Epidemiology

• Geographic Pathology
• Clinical Epidemiology
• Identification of Agents of Disease
• Statistical Epidemiology
• Field Survey for Specific Purposes
• Incidence Study (Longitudinal Study)
• Experimental Epidemiology
• Tracing Reservoirs and Sources of Infection
• Administrative Control of Disease

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Epidemiological Team

• Epidemiology is an applied science, at times it
  requires such divergent skill as those of
  physician, dentist, veterinarian, public health
  nurse, sanitarian, nutritionist, health educator,
  social worker, statistician, anthropologist,
  biochemist, meteorologist and others to work as a
  team.

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Contributing Factors

• Agent A
• Host H
• Environment E

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Interaction of A, H, E Dr. John Gordon
A
H
E
Balance
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Interaction of A, H, E Dr. John Gordon
H
A
E
Agent changes
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Interaction of A, H, E Dr. John Gordon
A
H
E
Host changes
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Interaction of A, H, E Dr. John Gordon
H
A
E
Environment changes facilitates agent spread
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Interaction of A, H, E Dr. John Gordon
A
H
E
Environment changes alters host susceptibility
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Natural History of Disease in man

• 2 Period
• Prepathogenesis Period
• Pathogenesis Period
• - Pre clinical Stage
• - Clinical Stage (Mild, Moderate, Severe)
• - Disability

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Post-interval equillibrium

• Recovery or Cure
• Chronic State
• Relapse
• Disability
• Defect
• Death