1. Introduction to Epidemiology Sumattana.g@ msu.ac.th

2. 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. 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.

3. Epidemiology for...  Epidemic diseasePast  Communicable disease  Non-communicable disease  Non-infectious disease Present  Chronic disease  Occupational disease  Environmental disease

4. EPIDEMIOLOG Y EPI=on, upon DEMOS= people, population LOGOS= knowledge, study doctrine, discourse science

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

6. 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)

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

8. 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.

9. 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.

10. 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.

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

12. 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.

13. Contributing Factors Agent A Agent A Host H Host H Environment E Environment E

14. Interaction of A, H, E ; Dr. John Gordon A H E Balanc e

15. Interaction of A, H, E ; Dr. John Gordon A H E Agent changes

16. Interaction of A, H, E ; Dr. John Gordon A H E Host changes

17. Interaction of A, H, E ; Dr. John Gordon A H E Environment changes facilitates agent spread

18. Interaction of A, H, E ; Dr. John Gordon A H E Environment changes alters host susceptibility

19. Natural History of Disease in man 2 Period Prepathogenesis Period Prepathogenesis Period Pathogenesis Period Pathogenesis Period - Pre clinical Stage - Clinical Stage (Mild, Moderate, Severe) - Disability

20. Post-interval equillibrium Recovery or Cure Recovery or Cure Chronic State Chronic State Relapse Relapse Disability Disability Defect Defect Death Death