Epidemiology Tools and Methods Session 2, Part 1

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

Overview Session 2, Part 1 Epidemiologic methods and resources Public health laboratories Data and technology Examples of tools in action

Epidemiology Methods

Epidemiologic Methods Person, place and time Exposure assessment Investigative field work and epidemiologic studies Data analysis techniques

References and Resources Scientific literature Control of Communicable Diseases Manual and other references State-specific manuals and epidemiology websites CDC website, references, experts

Public Health Laboratories

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

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

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

Data and Technology “Tools”

Sources of Data Surveillance systems Questionnaires, surveys, interviews Medical and health facility records

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.”

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

Surveillance Data as a Tool Establish baseline rate of disease Detect epidemics Estimate magnitude of a health problem Determine geographic distribution Facilitate planning

Surveillance Data Graphs Incidence rates of reported hepatitis A infections in Colorado and the United States,

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

Questionnaire and Interview Data Outbreak investigations Rapid needs assessments

1. Contact tracing Questionnaires and Interviews: Other applications Case- Patients High Risk Contact Contact’s Contact 2. Case follow up

Data Management and Analysis Computer software packages –Epi Info™ –SAS ® –SPSS ® –Stata ®

Epi Info Software Features: –Relational database structure –On screen data entry form –Data analysis –Data graphing –Data mapping

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

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

Example Tuberculosis

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

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?

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

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

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

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

References and Resources Association of Public Health Laboratories [Web site]. Available at: Accessed March 1, Centers for Disease Control and Prevention [Web site]. Available at: Accessed March 1, Smallpox Response Plan Guide (Version 3.0) [Web page]. Division of Bioterrorism Preparedness and Response, Centers for Disease Control and Prevention; June 23, Available at: Accessed March 1, National Laboratory System {Web page]. Division of Laboratory Systems, Centers for Disease Control and Prevention; July 12, Available at: Accessed March 1, 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: Accessed March 1,