Introduction to Epidemiology PDF

Community Health: CHP 310 Introduction to Epidemiology 1 Learning outcomes At the end of the session, the students should: ØUnderstand the term epidemiology and it is relation to public health ØDefine the term epidemiology as a science...

Community Health: CHP 310 Introduction to Epidemiology 1 Learning outcomes At the end of the session, the students should: ØUnderstand the term epidemiology and it is relation to public health ØDefine the term epidemiology as a science ØIdentify the different classifications of epidemiology ØDescribe the purpose and uses of epidemiology ØExplain the interrelation between the three components of the epidemiological Triangle. ØDescribe epidemiological factors (PPT that influence the diseasee pattern and its public health impact. Epidemiology and public health ØPublic health refers to collective actions to improve population health. Epidemiology is one of the tools for improving public health. ØEarly studies in epidemiology were concerned with the causes (etiology) of communicable diseases, and this can lead to the identification of preventive methods. What is Epidemiology? definition: “Last’s dictionary” “The 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”. John M. Last. A dictionary of Epidemiology. 4th Edition. 2001. Oxford University Press. New York.  to determine, describe, and report on the natural course of the disease Uses of to help in the planning and development Epidemiology of health services and programs to provide administrative data Objectives of Epidemiology ØTo study the cause (or etiology) of disease(s), conditions, disorders, disabilities, etc. ØTo determine the primary agent responsible or ascertain causative factors ØTo determine the characteristics of the agent or causative factors ØTo determine the mode of transmission ØTo determine contributing factors ØTo identify and determine geographic patterns Purpose of Epidemiology ØTo provide a basis for developing disease control and prevention measures for groups at risk.  Epidemiology Purposes in Public Health Practice q Discover the agent, host, and environmental factors that affect health q Determine the relative importance of causes of illness, disability, and death q Identify those segments of the population that have the greatest risk from specific causes of ill health q Evaluate the effectiveness of health programs and services in improving population health 8  Scope of epidemiology Epidemiology developed from the study of outbreaks of communicable disease and of the interaction between agents, hosts, vectors, and reservoirs. ´ The ability to describe the circumstances that tend to spark epidemics in human populations –e.g., during war, migration, famine, and natural disasters – has increased human ability to control the spread of communicable diseases through surveillance, prevention, quarantine, and treatment. Natural history and prognosis ØEpidemiologists are concerned with the natural history, (course and outcome), of disease, both in individuals and in groups. ØPrognosis often implies the course of disease after the intervention, but the terms tend to be used rather interchangeably. ØSuch knowledge has obvious value for discussing treatment options with individual patients, as well as for planning and evaluating interventions. ØOf particular interest is whether the early disease is present for long before symptoms drive someone to seek medical attention. If this ‘sub-clinical’ disease can be detected and if, as a result, treatment is more effective, this opens the way for screening programs that aim to improve treatment outcomes. Achievements in epidemiology The eradication of smallpox contributed greatly to the health and well-being of millions of people, particularly in many of the poorest populations. (1970). A good understanding of the epidemiology of smallpox was central to its eradication. providing information about the distribution of cases and the model, mechanisms, and levels of transmission; mapping outbreaks of the disease; evaluating control measures Ø Iodine deficiency diseases Ø Methyl mercury poisoning Ø Hip fractures Ø Rheumatic fever and rheumatic heart disease Ø HIV/AIDS Ø Tobacco use, asbestos, and lung cancer Ø Covid -19 Two Broad Types of Epidemiology: Covid-19 March 2020-June 2022 Ødescriptive epidemiology: examining the distribution of disease in a population and observing the basic features of its distribution. Øanalytic epidemiology: investigating a hypothesis about the cause (factors) of disease by studying how exposures relate to disease Most SARS-CoV-2 deaths were associated with older age, male sex. Descriptive Epidemiology: descriptive epidemiology is an antecedent to descriptive analytical analytical epidemiology (starting point): Analytical Epidemiology: analytical epidemiology studies require information to... Øknow where to look Øknow what to control for Ødevelop viable hypotheses Essential elements for Descriptive Epidemiology: Person ØThree essential characteristics of the disease we look for in descriptive studies are (PPT): Place Time Characteristics of the Person Øage, gender, ethnic group Øgenetic predisposition Øconcurrent disease Ødiet, physical activity, smoking Ø risk-taking behavior ØSocioeconomic status (SES), education, occupation  Characteristics of the Place (geographical) Øpresence of agents or vectors Øclimate Øgeology Øpopulation density Øeconomic development Ønutritional practices Ømedical practices  Characteristics related to Time Øcalendar time Øtime since an event Øphysiologic cycles Øseasonality Øtemporal trends The Epidemiologic Triangle (Triad) ØThe Epidemiologic Triangle: three characteristics that are examined to study the cause(s) of disease in analytic epidemiology Host Agent Environment The Epidemiologic Triangle Host Host Øpersonal traits Øbehaviors Øgenetic predisposition Agent Environment Øimmunologic factors What are the differences between the characteristics of the person and the host? The Epidemiologic Triangle Agent Ø Biological (e.g., viruses, bacteria, fungi, parasites, Host helimenthesis) Ø Physical (radiation, water, air, etc.,) Ø Chemical (toxins, minerals, gases, etc.,) Ø... Agent Environment Ø influence the chance for disease or its severity The Epidemiologic Triangle Environment Host ØMacro and microenvironment Øexternal conditions: atmosphere, hydrosphere, lithosphere, and biosphere Agent Environment Øphysical/biological/social All that contributes to the disease process What happens when those three elements (host, agent, and environment) were not in balance? An epidemic occurs Due to - a new agent (e.g. sars-2 virus: COVID-19) - change in the characteristics of the existing agent (infectivity, pathogenicity, virulence. E.g., Omicron vs. delta vs. Mers-Cov) - change in the number of susceptible in the population (due to migration or displacement) - environmental changes that affect the transmission of the agent or growth of the agent (new mosquito breeding places or prolonged breading time) Epidemiologic Activities Øoften concentrate on PPT (person, place, and time) Ødemographic distribution Øgeographic distribution Øseasonal patterns and temporal trends Øfrequency of disease patterns Epidemiologic Activities Øare built around the analysis of the relationship between Øexposures Ødisease occurrence Øare built around the analysis of differences between Øcases Øhealthy controls Epidemiologic areas of Activities Activities related to communicable diseases include epidemics and outbreaks. Activities were related to non-communicable diseases such as heart diseases, diabetes mellitus, obesity, renal failure, and more. Activities related to health conditions and risk factors: tobacco use, alcohol addiction, drug addiction, and suicidal tendencies. Leading causes of death globally qThe world’s biggest killer is ischaemic heart disease, responsible for 16% of the world’s total deaths in 2019. q Stroke and chronic obstructive pulmonary disease are the 2nd and 3rd leading causes of death, responsible for approximately 11% and 6% of total deaths, respectively. Further readings Ø Principles of Epidemiology in Public Health Practice. Third Edition. U.S. Department of Health and Human Services. Centers for Disease Control and Prevention (CDC). Office of Workforce and Career Development. Atlanta, GA 30333 Ø Basic epidemiology / R. Bonita, R. Beaglehole, T. Kjellstrom. 2nd edition. 2006 Ø Epidemiology. Manuals. Beaglehole, Robert. Kjellstrom, Tord. World Health Organization Ø Epidemiology for Public Health Practice. Robert H Friis, Thomas A. Sellers. 5th Edition 28 Thank you Any question