Principles of Surveillance: Definition, Objectives, and Major Systems

1. Principles of Surveillance Jonathan Samet, MD, MS Johns Hopkins Bloomberg School of Public Health

2. Learning Objectives • Define the basic terms related to surveillance • Specify characteristics of surveillance systems for different objectives • Describe selected major surveillance systems

3. Uses of Morbidity and Mortality Data • Hypothesis generation • Health planning • Program evaluation • Surveillance

4. Surveillance “Ongoing, systematic collection, analysis, and interpretation of health-related data essential to the planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination of these data to those responsible for prevention and control.” — U.S. Centers for Disease Control and Prevention

5. Information Loop of Public Health Surveillance Source: adapted by CTLT from http://www.cdc.gov/epo/dphsi/phs/overview.htm

6. Immediate Detection of . . . • Epidemics • Established agents • Emerging agents • Newly emerging health problems • Changes in health practices • Changes in antibiotic resistance • Chemical and biological terrorism Source: Thacker and Stroup. (1994).

7. Estimating the magnitude of the health problem, including costs Assessing control activities Setting research priorities Testing hypotheses Facilitating planning Monitoring risk factors Monitoring changes in health practices Periodic Dissemination for . . . Source: Thacker and Stroup. (1994).

8. Archival Information for . . . • Describing the natural history of disease • Facilitating epidemiologic and laboratory research • Validating the use of preliminary data • Setting research priorities • Documenting distribution and spread Source: Thacker and Stroup. (1994).

9. Langmuir on Surveillance “Surveillance, when applied to a disease, means the continued watchfulness over the distribution and trends of incidence through the systematic collection, consolidation, and evaluation of morbidity and mortality reports and other relevant data.” — Alexander Langmuir

10. From Vector to Agent to Disease: Surveillance Points

11. Points for Surveillance Example: Tobacco

12. Modeling a Surveillance System Source: Teutsch and Churchill. (2000).

13. Surveillance Systems: Some Characteristics • Geographic scale: local to global • Event identification: active or passive • Scope: all or sentinel events • Focus on monitoring: vector  agent  outcome • Purpose: tracking or alarm

14. Modeling a Surveillance System Source: Teutsch and Churchill. (2000).

15. Occurrence of an Event: Kind of Event • What kind of an event? • Exposure • Exposure to air pollution, bio-monitoring • Disease • Communicable diseases, chronic diseases, syndromes • Injuries • Motor vehicle accidents, homicide • Health risk factors • Obesity • Health behaviors • Smoking, sexual behavior, substance use

16. Occurrence of an Event: Surveillance of What? • What do you want to do a surveillance of? • Exposure • Agents • Biomarkers • Exposure determinants • Behaviors • Risk factors • Vectors • Host characteristics • Reservoirs • Health outcomes • Disease • Death • Medical care

17. WHO Global Tobacco Surveillance • World Health Survey • Household survey of adults (18+) conducted in 70 countries in 2002–2003 • STEPwise Approach to Surveillance (STEPS) • Modular survey of chronic disease risk factors • Global Youth Tobacco Survey • School-based survey • Global Adult Tobacco Survey (planned)

18. Occurrence of an Event: What Type of System? • What type of system would work best? • Universal: population tracking • Choose entire population or a representative sample to monitor for condition of interest (measles, obesity, bioterrorism agents) • Sentinel: “warning” signs • Choose key “location” to monitor for condition of interest (e.g., unusual disease) • “Locations” might include sites, events, providers, animals, vectors • Choose a “location” that is most susceptible to change

19. Capturing an Event: Approaches • Active • Periodic solicitation of case reports from reporting sources, such as physicians, hospitals, laboratories, etc. • Passive • Relies on health care providers to report on their own initiative • Must make this reporting process simple and time efficient

20. Active Advantages Can be very sensitive Can collect more detailed information May be more representative Disadvantages Costly Labor intensive Difficult to sustain over time Passive Advantages Less costly Eager to design and carry out Useful for monitoring trends over time Disadvantages Low sensitivity Amount of data available is limited May not be representative Active vs. Passive: Advantages and Disadvantages

21. Active: SEER Cancer Registry Source: http://seer.cancer.gov

22. Passive: CDC Notifiable Diseases Provisional Cases of Selected Notifiable Diseases, United States,Week Ending July 16, 2005* * Incidence data for reporting year 2005 is provisional Source: U.S. Centers for Disease Control. (2005).

23. Modeling a Surveillance System Source: Teutsch and Churchill. (2000).

24. Processing and Analyzing the Event • How do you detect a signal? • Data capture/editing/management • Analytical approaches • Statistical approaches

25. Examine the Event by Person, Place, and Time • By person: demographics, lifestyle, risk factors • By place: GIS mapping • By time: epidemic curve, time series analysis

26. By Place: GIS Mapping • GIS: geographic information systems • GIS links location to information (such as people to addresses, buildings to parcels, or streets within a network) and layers that information to give you a better understanding of how it all interrelates • You choose what layers to combine based on your purpose

27. By Time: Time Series • Time series analysis accounts for the fact that data points taken over time may have an internal structure (such as trend or seasonal variation) that should be accounted for Image source: adapted by CTLT from U.S. Centers for Disease Control and Prevention. (2005).

28. By Person: Demographics • Age • Race/ethnicity • Occupation • Socioeconomic status • Sex

29. By Place • Small areas • Governmental units • Nations Unit chosen to examine is determined by the availability of data on particular geographic scales

30. Cancer Mortality Rates, by State Source: U.S. National Cancer Institute. (1999).

31. Heart Disease Death Rates: 1991–1995 Source: U.S. Centers for Disease Control and Prevention.

32. Male Lung Cancer Incidence Rate per 100,000 Source: adapted by CTLT from GLOBOCAN. (2002). IARC.

33. Female Lung Cancer Incidence Rate per 100,000 Source: adapted by CTLT from GLOBOCAN. (2002). IARC.

34. Modeling a Surveillance System Source: Teutsch and Churchill. (2000).

35. Disseminating the Information • Process information for your audience • Broadcast faxes, email, mailings to dissemination lists • Locally, to clinicians • Regionally, to health departments • Web sites • Journal articles • Media

36. Tobacco Use Information Systems • Global InfoBase • Data repository for chronic disease risk factor prevalence, including tobacco use • Summarized in Surveillance of Risk Factors Report (SuRF) • Global Information System on Tobacco Control (GISTOC) • Provides links to tobacco-related databases Image source: World Health Organization. (2003 and 2005).

37. World Health Organization: The SuRF Report Source: The World Health Organization.

38. Modeling a Surveillance System Source: Teutsch and Churchill. (2000).

39. Response Hypothesis generation Health planning Program evaluation Model for State-Based Chronic Disease Surveillance Source: Remington and Goodman. (1999).

40. Summary • Surveillance takeaways • Ongoing collection • Systematic according to a plan • Results given to those who need to know them • Resulting action is based in evidence gained in the surveillance system