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
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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20
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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