Part 1 DESCRIPTIVE EPIDEMIOLOGY 1

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

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

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

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

Clinical Features Symptoms Signs Laboratory findings Hospitalization Death

Outbreak of Group A Strep Pharyngitis – Clinical Features (n = 100) Sore throat100 / % Swollen glands82 / % Headache82 / % Fever78 / % Muscle aches52 / % Stomach ache45 / % Vomiting15 / % See physician?59 / % Culture taken?29 / % (Culture positive23 / %) Hospitalized?0 / %

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

Time Secular trend Seasonal pattern Epidemic

Secular Trend 10

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

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

Reported Tuberculosis Cases, United States, No. of Cases Year Source:

Seasonal Trend

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

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

Epidemic/Outbreak 17

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

Salmonella Enteritidis Infections by Date of Onset, Maryland, August /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

Place Residence of cases Worksite Location of exposure

Laboratory-confirmed West Nile Virus Human Cases, August–September, 1999

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

Positive Dengue Cases by Age and Sex 26

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

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

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

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