INTRODUCTION TO EPIDEMIOLOGY By: Dr. Ismail Zubair M.D, MSc HPM

LEARNING OBJECTIVES At the end of this session the participants will be able to:  Discuss the historical evolution of epidemiology  Explain the usage of epidemiology  List the core epidemiological functions  Explain types of epidemiological studies

EPIDEMIOLOGICAL PRINCIPLES  Diseases (or other health events) don’t occur at random  Diseases (or other health events) have causal and preventive factors which can be identified

EPIDEMIOLOGY Epi = upon Demos =population Logos = study of

HISTORY From Hippocrate … … To John Snow ! cholera 1854

Cholera 1854 investigation CHOLERA MAP

JOHN SNOW PILLAR OF EPIDEMIOLOGY  On 31 August 1854, after several other outbreaks had already occurred elsewhere in the city, a major outbreak of cholera struck Soho. Dr. Snow later called it "the most terrible outbreak of cholera which ever occurred in the kingdom."  Over the next three days 127 people on or near Broad Street died  In the next week, three quarters of the residents had fled the area  By 10 September, 500 people had died and the mortality rate was 12.8 percent in some parts of the city  By the end of the outbreak 616 people died

JOHN SNOW AND CHOLERA  The miasmatic theory of disease held that diseases such as cholera, Chlamydia or the Black Death were caused by a miasma (Greek language: "pollution"), a noxious form of "bad air".diseases choleraChlamydiaBlack Death

JOHN SNOW AND CHOLERA  This concept has been supplanted by the germ theory of disease.germ theory of disease  also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases. Although highly controversial when first proposed, it is now a cornerstone of modern medicine and clinical microbiology, leading to such important innovations as antibiotics and hygienic practicestheorymicroorganismsmicrobiologyantibioticshygienic practices

JOHN SNOW AND CHOLERA  In 19th century sanitory reforms was repalced by sanitory science depending on germ theory  Based on Epidemiology Science, Public health began to focus on preventive measures  By decline of the infectious disease and emmergence of the new set of diseases related to lifestyle in the mid 20th, the profile of public health became low...

DEFINITION OF EPIDEMIOLOGY The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems Last, 1988

KEY WORDS (I)  The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Distribution  Time, place, person

KEY WORDS (II) The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Determinants  Cause, risk factors

KEY WORDS (III) The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Population  Public health

KEY WORDS (IV) The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Application  Information for action

Epidemiology is?

USE OF EPIDEMIOLOGY Determine the magnitude and trends Identify the etiology or cause of disease Determine the mode of transmission Identify risk factors or susceptibility Determine the role of the environment Evaluate the impact of the control measures

CORE EPIDEMIOLOGIC FUNCTIONS Public health surveillance Outbreak investigations Data analysis Evaluation of disease control programs Communication Management and teamwork

Target/Evaluat e Analyze Intervene Communicate Analytic epidemiology defines risk factors Descriptive epidemiology, surveys, surveillance, Quality assurance Communications to decision makers, media, on problem and risk factors. Management, advocacy, communications Evaluate population health and program output, repeat cycle Public health cycle 19

BASIC EPIDEMIOLOGICAL APPROCH  Observe  Count cases (events)  Describe  Time, place, person  Calculate rates,  Compare rates  Develop hypotheses  Test hypotheses  Implement actions (control, prevention) Descriptive Epidemiolo gy Analytical Epidemiology

DESCRIPTIVE VS. ANALYTIC  Descriptive: Activities related to characterizing the patterns of disease occurrence in terms of person, place or time. Hypothesis Generating  Analytic: Activities related to identifying possible causes for the occurrence of disease. Hypothesis Testing

DESCRIPTIVE EPIDEMIOLOGY STRENGTHS AND LIMITATIONS  Inexpensive  Time saving  Describe disease patterns  Formulate research questions  Unable to test epidemiologic hypotheses

DISTRIBUTION  How common is the disease?  Who gets disease?  Where does the disease occur?  When does the disease occur ?

DESCRIPTIVE EPIDEMIOLOGY - PERSON  Disease does not occur at random.  Not all persons within a population are equally likely to develop a particular disease.

DESCRIPTIVE EPIDEMIOLOGY - PERSON Variation of occurrence in relation to personal characteristics may reflect differences in level of:  exposure to causal factors  susceptibility to causal factors  the need for some level of both susceptibility and exposure

DESCRIPTIVE EPIDEMIOLOGY - PERSON Personal characteristics that are commonly examined with respect to disease occurrence are:  age  race  gender  marital status  education  income  occupation

DESCRIPTIVE EPIDEMIOLOGY - PERSON Reported cases of Tuberculosis by age in country X, in 1992

DISTRIBUTION  How common is the disease?  Who gets disease?  Where does the disease occur?  When does the disease occur ?

DESCRIPTIVE EPIDEMIOLOGY - PLACE  Where are the disease rates highest?  Where are the disease rates lowest?  Does the disease rate vary by country, region, etc?

DISTRIBUTION  How common is the disease?  Who gets disease?  Where does the disease occur?  When does the disease occur?

DESCRIPTIVE EPIDEMIOLOGY - TIME  When is the disease common?  When is the disease rare?  Is the frequency of the disease in the present different from the frequency of the disease in the past?

DESCRIPTIVE EPIDEMIOLOGY - TIME Reported cases of Tuberculosis by year in country X during the period

TYPES OF EPIDEMIOLOGICAL STUDIES

EPIDEMIOLOGY AND PREVENTION

Thank you