2 Basic Concept in Epidemiology Epidemiology is the study of the occurrence, distribution and determinants of health problems and diseases in human population or communities and the use of this knowledge for prevention and control of diseases.The primary unit of concern is a group of person not any single person. Therefore epidemiology deals with population pathology not the clinical pathology.
3 Word “Epidemiology” is derived from Greek words: Epi= upon , onDemos= peopleLogus= study, knowledgeThus epidemiology in its broadest sense is the study of effects of various things on people.
4 The evolutions of Definitions of Epidemiology Historical definition “The science and doctorine of epidemics”( New standard dictionary of English Language)The science of epidemics and epidemic disease.( stedmans practical medical dictionary)The science of mass phenomena of infectious disease or the natural history of infectious diseases ( Frost, 1927)The science of infective diseases, their prime causes, propagation and prevention(Stallybrass, 1931)Study of disease, any disease, as a mass phenomena-(Greenwood 1932)
5 Modern MeaningEpidemiology 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 the pattern of diseases and the factors that cause disease in man( CDC, US Public health services)“The study of the frequency, distribution and determinants of disease in human population" - Mac Mohan and Pugh
6 A widely accepted definition is “the study of distribution and determinants of health related states and events in specified populations, and the application of this study to control of health problems"-Last, 1988
7 Three important components included in these definitions are: FrequencyDistributionDeterminants
8 The first component to be considered is measurement of disease frequency, which involves quantification of the occurrence of disease.The second component is distribution of disease in terms of time, place, and person- who is getting the disease, where and when the disease is occurring.The third component, the determinant of disease derives from the first two, since knowledge of frequency and distribution of disease is necessary to test an epidemiological hypothesis.
9 Aims of epidemiologyTo describe the distribution and size of disease problems in human populations. (Descriptive epidemiology)To identify the etiological factors in the pathogenesis of disease (Analytical epidemiology)To provide the data essential in planning, implementation and evaluation of services for the prevention, control and treatment of disease and setting up priorities among those services.(Experimental epidemiology)
10 The ultimate aim of epidemiology is to eliminate or reduce the health problem or its consequencesto improve medical care and provide administrative guidance for community health servicesto promote the health and well being of society as a whole
11 Functions/Uses of epidemiology To find causation of the diseaseTo describe natural historyDescription of health status of populationsEvaluation of interventionCommunity diagnosisPlanning and evaluationInvestigate epidemics of unknown etiologyElucidate mechanism of disease transmission
12 Scope of epidemiologyDisease definition: characteristics or combination of character that best discriminate disease from non diseasedDisease occurrence: the rate of development of new case in population. The proportion of current disease within populationDisease causation: the risk factors for disease development and their relative strength with respect to an individual and populationDisease outcome: the outcome following disease onset and of the risk factors.Disease management: the relative effectiveness of proposed therapeutic interventionsDisease prevention: the relative effectiveness of proposed preventive strategies including screening
13 Comparison between Epidemiology and Clinical Medicine SubjectsEpidemiologyClinical MedicineUnit of studyDefined population or population at riskCase or casesExaminationSurvey of particular communitypatientsConcern withBoth sick and healthy peopleCases with disease patternDiagnosisPeople/ community diagnosisPatients diagnosis with the help of signs and symptomsObjectiveTo identify particular source of infection, mode of transmission, aetiological factors, ways of controlling these problems and continuous follow upTo diagnose, prognosis and prescribe specific treatment for the diseases within limited period of timeRelationshipEpidemiological team goes to community to find and solve health problemPatient come to the doctor for treatmentArea concernConcern with preventive and promotive measureConcern with curative measureConceptBiostatisticalBiomedicalResultSymbolized in the form of tables and graphsSymbolized as medical and laboratory reportTimeSustainable and long processQuick and short result