Learning Objectives Session 2, Part 1 List methods that can be
used for epidemiologic assessment of a health problem Identify ways
that public health laboratories carry out epidemiologic functions
Identify ways that data can be collected during an epidemiologic
investigation
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Overview Session 2, Part 1 Epidemiologic methods and resources
Public health laboratories Data and technology Examples of tools in
action
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Epidemiology Methods
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Epidemiologic Methods Person, place and time Exposure
assessment Investigative field work and epidemiologic studies Data
analysis techniques
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References and Resources Scientific literature Control of
Communicable Diseases Manual and other references State-specific
manuals and epidemiology websites CDC website, references,
experts
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Public Health Laboratories
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What Do Public Health Laboratories Do? 1.Disease prevention,
control, and surveillance 2.Integrated data management 3.Reference
and specialized testing 4.Environmental health and protection
5.Food safety 6.Laboratory improvement and regulation 7.Policy
development 8.Emergency preparedness and response 9.Public health
research 10. Training and education 11. Partnerships and
communication
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Laboratory Surveillance, Monitoring, Reporting Surveillance
Vector borne diseases Communicable diseases Food borne and
waterborne diseases Monitoring Newborn screening and genetics
Radiation monitoring and detection Food safety or other
environmental issues Reporting Two-way with state health
departments
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Association of Public Health Laboratories (APHL) Purpose
Promote the role of public health laboratories Promote improvement
in laboratory practice and health outcomes Programs Environmental
health Food safety Public health preparedness and response Working
relationship with CDC, EPA, FBI, DHS
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Data and Technology Tools
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Sources of Data Surveillance systems Questionnaires, surveys,
interviews Medical and health facility records
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Surveillance The ongoing systematic collection, analysis, and
interpretation of health data, essential to the planning,
implementation, and evaluation of public health practice, closely
integrated with the timely dissemination to those who need to
know.
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Physicians Laboratories STD clinics Community health clinics
Physicians Laboratories STD clinics Community health clinics County
and state health departments, CDC analyze data using statistical
methods Public health officials Health directors Health policy
officials The public Public health officials Health directors
Health policy officials The public Change in public health practice
(vaccination, reduction of risk factors, medical intervention,
etc.) Standardized data collection Dissemination to those who need
to know Public health planning and intervention Public health
evaluation Surveillance Information, Dissemination, and
Reporting
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Surveillance Data as a Tool Establish baseline rate of disease
Detect epidemics Estimate magnitude of a health problem Determine
geographic distribution Facilitate planning
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Surveillance Data Graphs Incidence rates of reported hepatitis
A infections in Colorado and the United States, 2000-2009
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Surveillance Data Maps North Carolina Salmonella Rates by
County: 2002 Rate numerators: NC Communicable Disease Data for 2000
Rate denominators: U.S. Census population data, by county, for 2000
Salmonella rate
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Questionnaire and Interview Data Outbreak investigations Rapid
needs assessments
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1. Contact tracing Questionnaires and Interviews: Other
applications Case- Patients High Risk Contact Contacts Contact 2.
Case follow up
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Data Management and Analysis Computer software packages Epi
Info SAS SPSS Stata
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Epi Info Software http://wwwn.cdc.gov/epiinfo/
http://wwwn.cdc.gov/epiinfo/ Features: Relational database
structure On screen data entry form Data analysis Data graphing
Data mapping
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Epidemiologic Software Store databases Surveillance systems
Outbreak investigations Medical records Generate descriptive
statistics Frequencies, proportions, rates Graphs: bar, line,
histogram (Epi Curves) Maps: census tracts; counties; districts
Generate statistics Test statistics: t-test, chi-square Measures of
association: Odds ratios, risk ratios
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The Epidemiologist Generate hypotheses Make judgments about
linkages between exposure and outcome Interpret data Identify or
correct mistakes Interpret statistical and laboratory tests Make
decisions Determine if an epidemic is in progress Recommend control
measures
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Example Tuberculosis
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TB Exposure Investigation Background Hospital nurse with active
TB died Several unknowns: Duration of infectiousness Number of
patients exposed Number of hospital visitors exposed Identity of
hospital visitors
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Data-Based Decisions Interviews Nurse family members Hospital
patients and visitors Result Infectious period: July 2003-April
2004 Need to screen 900 patients and 1500 visitors Further
questions Does the time period for exposure need to be expanded?
Did exposed persons spread disease to their own contacts? Were
high-risk patients exposed? What are the TB reaction rates among
patients, contacts?
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Investigation and Response Finding social and professional
contacts Coordinating three districts Hospital employee and staff
screening Screening and testing patients and visitors Approximately
900 patients & 1500 visitors Requesting outside help
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Outcomes 2500 people screened 2300 tuberculin skin tests 2100
(92%) read 128 positives More than 350 x-rays 120+ hours of clinic
time New TB testing policy and employee illness monitoring at the
hospital
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Tools Used To find and screen contacts:To interpret results:
ComputersAnalytical tools Administrative capacityCommunications
Interview instrumentsPolicy development for infection control
Reference journals and institutions Laboratory Diplomacy
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Summary Epidemiologists employ investigative and analytic tools
to collect data and assess factors that cause disease Laboratories
play a role in diagnosis and surveillance for carrying out public
health investigations and core epidemiologic functions Statistical
software is used for data management and analysis Human effort is
used to investigate, generate hypotheses, and interpret
results
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References and Resources Association of Public Health
Laboratories [Web site]. Available at: http://www.aphl.org.
Accessed March 1, 2012. http://www.aphl.org Centers for Disease
Control and Prevention [Web site]. Available at:
http://www.cdc.gov. Accessed March 1, 2012. http://www.cdc.gov
Smallpox Response Plan Guide (Version 3.0) [Web page]. Division of
Bioterrorism Preparedness and Response, Centers for Disease Control
and Prevention; June 23, 2004. Available at:
http://www.bt.cdc.gov/agent/smallpox/response-plan. Accessed March
1, 2012. http://www.bt.cdc.gov/agent/smallpox/response-plan
National Laboratory System {Web page]. Division of Laboratory
Systems, Centers for Disease Control and Prevention; July 12, 2004.
Available at: http://www.phppo.cdc.gov/mlp/nls.aspx. Accessed March
1, 2012. http://www.phppo.cdc.gov/mlp/nls.aspx Inhorn SL, Astles
JR, Gradus S, et al. The State Public Health Laboratory System.
Public Health Rep. 2010; 125(Suppl 2):4-17. Available at:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846798/. Accessed
March 1, 2012.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846798/