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Part 1 DESCRIPTIVE EPIDEMIOLOGY 1

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Objectives Describe the components of descriptive epidemiology Describe the uses and importance of descriptive epidemiology Describe what tables, graphs, and charts might be used to present descriptive epidemiology to an audience or decision-makers

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Epidemiology Basic science of public health Data-driven Systematic collection, analysis and interpretation of data Distribution and determinants of health-related states or events Application to the control of health problems 3

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What is Descriptive Epidemiology? Portrays the pattern of disease occurrence in terms of (Clinical features) Time Place Person Defines the relationship of disease occurrence to the population at risk

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Distribution What Who Where When Why / How =Clinical =Person =Place =Time =Cause, Risk factors, modes of transmission Descriptive Epidemiology (Distribution) or

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Clinical Features Symptoms Signs Laboratory findings Hospitalization Death

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Outbreak of Group A Strep Pharyngitis Clinical Features (n = 100) Sore throat100 / 100100.0% Swollen glands82 / 9487.2% Headache82 / 9586.3% Fever78 / 9582.1% Muscle aches52 / 9753.6% Stomach ache45 / 9646.9% Vomiting15 / 9316.1% See physician?59 / 9760.8% Culture taken?29 / 9131.8% (Culture positive23 / 2688.5%) Hospitalized?0 / 1000.0%

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Outbreak of Group A Strep Pharyngitis Clinical Features (n = 100)

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Time Secular trend Seasonal pattern Epidemic

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Secular Trend 10

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Secular Trend Secular trend = long-term trend of disease occurrence, usually by year

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Reported Tuberculosis Cases, United States 12 In 2010, there were 11,182 cases of TB reported in the U.S.

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Reported Tuberculosis Cases, United States, 1981-2010 No. of Cases Year Source: http://wonder.cdc.gov/tb-v2007.html

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Seasonal Trend

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Seasonal trend = cyclical pattern during particular weeks or months of the year, seen consistently over years

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Proportionate Pneumonia & Influenza Deaths, 122 U.S. Cities, 2005 2010

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Epidemic/Outbreak 17

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Epidemic/Outbreak Epidemic/Outbreak = An increase in incidence above the expected in a defined geographic area within a defined time period

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Salmonella Enteritidis Infections by Date of Onset, Maryland, August 2003 8/218/228/238/248/258/268/27 No spaces between adjacent columns Date and Time of Onset

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Measles Marshall Islands, 2003 International Journal of Epidemiology (2006) J. Han July Nov 2003 >800 cases, 100 hospitalizations, 3 deaths 21

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Place Residence of cases Worksite Location of exposure

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Laboratory-confirmed West Nile Virus Human Cases, AugustSeptember, 1999

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Person AgeMarital status SexReligion OccupationTravel Immunization statusPets Underlying diseaseHobbies MedicationsPersonal habits Nutritional statusGenetics Socioeconomic status

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Positive Dengue Cases by Age and Sex 26

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Typical Descriptive Epi Table Example 1 Ortiz, Katz, Mahmoud, et al. J Infect Dis 2007;196:1685-1691

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Typical Descriptive Epi Table Example 2 Lee et al. J Infect Dis 2009;200:492-500.

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Why is it Important to Perform Descriptive Epi? Describe clinical characteristics of the illness Describe demographic characteristics of those affected Identify or infer population at risk Provide clues to etiology, modes of transmission Guide interventions

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Summary Epidemiology is 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 Descriptive epidemiology (time, place, person, clinical) is an essential part of epidemiology, particularly but not limited to field epidemiology The basic approach to field investigations is count, divide (calculate proportions or rates), compare to identify high risk groups, risk factors, and causes so action can be taken