Mapping for Surveillance and Outbreak Investigation

1. Mapping for Surveillance and Outbreak Investigation

2. Mapping for Surveillance and Outbreak Investigation This issue of FOCUS was adapted from the following online training on the NCCPHP Training Web Site (http://nccphp.sph.unc.edu/training/): Infectious disease surveillance and outbreak investigation using GIS (2004) Dionne Law, PhD, Spatial Epidemiology Research Associate Department of Epidemiology, University of North Carolina at Chapel Hill

3. Goals • Describe ways maps can be used in field epidemiology • Describe how geographic information systems (GIS) can display and analyze spatial data • Provide examples of surveillance and outbreak investigation activities that relied on GIS • Describe the use of global positioning systems (GPS) to increase GIS capabilities

4. Mapping for Surveillance and Outbreak Investigation • Maps are commonly used in epidemiology to present complicated information succinctly and clearly • This issue discusses: • How maps can be used in field epidemiology • Commonly used computer software programs that can capture and analyze data and integrate them into a spatial display

5. Maps • Earliest documented epidemiologic study relied on mapping • Dr. John Snow’s investigation of cholera outbreak, London, 1854 • Used maps and statistical data to trace source of outbreak to public water pump on Broad Street 

6. Maps • Most noted example of maps to convey complicated statistical information comes from outside public health (1) • 1869 map of French army’s march to and retreat from Moscow • Displays multivariate data (army size, direction, geographic location, temperature, and time)

7. Maps • Line widths show size of French army on advance to Moscow (tan) and retreat (black) • Chart below lines plots temperature

8. Maps • Map created during disease surveillance and response activities around avian influenza, rural Indonesia, 2005 (2) • Created using participatory mapping • Shows the sequence of events during outbreak of highly pathogenic H5N1 avian influenza in poultry in a small village 

9. Maps • Initially spread from House 1 to House 5; also in second village (6) and broiler farm (top right) Photo credit: Dr Gavin Macgregor-Skinner/USAID

10. Maps • Subsequent investigation revealed that residents of House 1 and households in second village worked at broiler farm • Probably introduced H5N1 virus into communities by carrying it home on shoes and clothing

11. Geographic Information Systems • Geographic information system (GIS): a computer program designed to store, manipulate, analyze, and display data in a geographic context • GIS capabilities are ideal for use in infectious disease surveillance and control, outbreak investigation and response

12. Geographic Information Systems • GIS can help: • Optimize data collection and management • Strengthen data analysis • Strengthen outbreak infrastructure and support • Map epidemic dynamics in near real-time • Quickly plan and target response • Rapidly communicate information • Monitor changes in disease over time • Plan, monitor intervention/eradication programs • Aid emergency preparedness

13. GIS Example: West Nile Virus • GIS displays information in map “layers” • Example: West Nile virus • Street network • Buildings: enclosures for sentinel species (chicken coops, horse stalls), offices, dwellings • Population at risk • Maps of land cover, digital elevation, precipitation, temperature, water features, veterinarians/physicians

14. GIS Example: West Nile Virus • After data is entered into GIS tool, you can… • Maintain surveillance of case-patient locations and progression of disease for early outbreak detection • Identify areas ideal for mosquito breeding and apply preventive measures • Predict which populations are vulnerable to infection based on proximity to breeding grounds • Simulate how an epidemic could evolve given introduction of infected mosquitoes/birds at various locations • Determine where to target interventions, strengthen healthcare resources

15. Surveillance and GIS Example:Public Health Mapping Programme • Developed in 1993 by WHO and UNICEF to eradicate Guinea worm disease • GIS used to: • Visualize disease foci • Monitor newly infected or re-infected villages, • Identify populations at risk • Target cost-effective interventions • Monitor eradication efforts

16. Surveillance and GIS Example:Public Health Mapping Programme • Technology developed to control one disease can enhance control of others • Since Guinea worm project, GIS and mapping expanded to meet data needs for: • Onchocerciasis (river blindness) • Blinding trachoma • African trypanosomiasis (sleeping sickness) • Lymphatic filariasis (elephantiasis) • Poliomyelitis • Malaria

17. Surveillance and GISExample: HealthMapper • Elimination of lymphatic filariasis possible through • Mass drug administration to those at risk • Promotion of intensive hygiene on affected body parts • Populations at risk, size, location not identified • HealthMapper enabled countries to estimate prevalence of disease at district level, identify precise areas to target for mass drug administration • Also tool for standardizing surveillance, monitoring indicators in different countries and regions (3)

18. Surveillance and GIS Example: Roll Back Malaria Partnership • Global partnership to enable effective, sustainable action against malaria • WHO strategy includes prompt treatment with effective drugs, vector-control methods, preventive treatment in pregnancy, emergency and epidemic preparedness and response • Developed GIS to: • Strengthen surveillance at local level for early detection, response to epidemics • Complement existing national/international health monitoring systems • Integrate information on community interventions, control interventions, private and public health providers, partner intervention areas, resources • Be accessible at different levels

19. Surveillance and GIS Example:US West Nile Virus Surveillance • CDC developed national surveillance plan for WNV to monitor spread of infection, provide national/regional information, identify regional distribution and incidence of other arbovirus diseases • GIS used to enhance federal surveillance system, communicate results to the public

20. Surveillance and GIS Example:US West Nile Virus Surveillance • CDC, US Geological Survey mapped mosquito, wild bird, horse, human populations • Tracked in sentinel species (chickens) 2007 U.S. Geologic Survey

21. Surveillance and GIS Example:US West Nile Virus Surveillance • Pennsylvania developed network to combat WNV • Covers all 67 counties • Includes trapping mosquitoes, collecting dead birds, monitoring horses, people, chickens • WNV Tracking System: spatially-driven surveillance program for following, responding to spread of WNV • Collects information on presence of virus, identifies mosquito-breeding areas, helps target control efforts • Alerts decision makers of new data via e-mail • Generates, posts detailed maps on secure Web site • Data for public release published on WNV Surveillance Program Web site (www.westnile.state.pa.us/)

22. Outbreak Investigation and GIS • GIS used to: • Strengthen data collection, management, and analysis • Develop early warning systems • Plan and monitor response programs • Communicate large volumes of complex information in simple, effective way to decision makers and public

23. Outbreak Investigation and GIS Example: Shigellosis • Fort Bragg, North Carolina, 1997 (4) • 59 cases of Shigellasonnei reported among military health beneficiaries • Significant number of cases were children • Preliminary investigation did not reveal associations with daycare or common location • Outbreak persisted despite education about hand washing and hygiene

24. Outbreak Investigation and GIS Example: Shigellosis • Imported addresses of all confirmed cases into GIS and mapped onto Fort Bragg housing areas • Revealed cluster of infections on several streets in one particular neighborhood

25. Outbreak Investigation and GIS Example: Shigellosis • Interviews with case families, neighbors revealed presence of small communal wading pools in several yards that were frequented by affected children • Once pools were removed and home-based information campaigns were initiated, spread of illness was halted

26. Outbreak Investigation and GIS Example: STIs • GIS also used to map sexually transmitted infections • Used in Baltimore to map distribution of syphilis before, during, after outbreak (5) • Data suggested that disease spread outward from 2 central cores of infection

27. Outbreak Investigation and GIS Example: STIs • Used to map distribution of 4 sexually transmitted infections (chlamydia, gonorrhea, syphilis, and HIV infection) in Wake County, NC (6) • Found clearly defined spatially heterogeneous areas of infection for different diseases 

28. Global Positioning Systems • Global positioning systems (GPS) add function to GIS, increase capabilities • A critical tool for precise identification of research subjects, locations, distances to related geographic features • Allow users to locate positions on electronic map using satellite technology

29. Global Positioning Systems Example: Atrazine Exposure • RTI International employed GPS-enabled handheld technology in a National Cancer Institute study to determine relationship between exposure to atrazine and distance from fields where used (7) • Required field trips to verify locations of households in study area near corn fields in Illinois • Used HP iPAQ Pocket PC with GPS receiver and ESRI's ArcPad® software (GIS software for mapping that allows capture, display, analysis of geographic information on handheld devices)

30. Global Positioning Systems Example: Atrazine Exposure • Candidate household addresses geocoded to street database, loaded onto ArcPad with aerial photographs, street centerline database • Staff used GPS, street names to find approximate location of households • Modified original address-matched location (green dots) to actual location (red dots) based on GPS and rooftops on aerial map • If households not seen on map, GPS coordinate on street captured

31. Global Positioning Systems Example: Atrazine Exposure • Measured household's distance from corn field where atrazine used • Concentrations of atrazine in household, in biological samples from occupants correlated with distance from atrazine source • Using ArcPad/GPS instead of paper maps • Allowed quick navigation from household to household • Made repositioning of household locations more accurate • Would have been almost impossible to do under study’s time constraints without this technology • Precisely measured household locations and precise distances from households to corn fields provided higher precision during data analysis

32. Global Positioning Systems • Approach could be applied to infectious disease surveillance and outbreak investigation and response • To measure distance to exposure (e.g., water source with cryptosporidium or farm with hoof and mouth disease) • Outbreak investigation and response are time-limited activities: must be done quickly to have greatest effect • GIS and GPS can greatly speed field work

33. Summary • Spread of disease — especially infectious disease — is unavoidably spatial • Infection moves from individual to individual following network of contacts within population through local or global transmission • GIS capacity to capture geospatial information ideally suited for infectious disease surveillance and control; highly relevant to meet demands of outbreak investigation and response • Next issue will show how GIS used to conduct rapid needs assessments

34. Additional Resources for GIS Mapping • World Health Organization Public Health Mapping Programme http://www.who.int/health_mapping/en/ • WHO HealthMapper http://www.who.int/health_mapping/tools/ healthmapper/en/index.html • Roll Back Malaria Partnership http://www.rbm.who.int/

35. Further Readings • Melnick, Alan L. Introduction to geographic information systems in public health. Gaithersburg, Md: Aspen Publishers; 2002. • Cromley, Ellen K. GIS and public health. New York: Guilford Press; 2002. • Moore DA, Carpenter TE. Spatial Analytical Methods and Geographic Information Systems: Use in Health Research and Epidemiology. Epidemiologic Reviews. 1999;21(2):143-160.

36. References • Tufte ER, The Visual Display of Quantative Information. 2nd ed. Cheshire, CT: Graphics Press, LLC; 1983:176. • Macgregor-Skinner G. Avian influenza H5N1: Getting our ducks in a row. Presentation at: 5th Annual “One Medicine” Symposium; December 12-13, 2007; Durham, NC. • Brooker S, Beasley M, Ndinaromtan M, et al. Use of remote sensing and a geographical information system in a national helminth control programme in Chad. Bulletin of the World Health Organization. 2002;80:783-789. • McKee KT, Shields TM, Jenkins PR, Zenilman JM, Glass GE. Application of a geographic information system to the tracking and control of an outbreak of shigellosis. Clin Infect Dis. 2000;31:728-733.

37. References • Gesink Law DC, Bernstein KT, Serre ML, et al. Modeling a syphilis outbreak through space and time using the Bayesian maximum entropy approach. Ann Epidemiol. 2006;16:797-804. • Law DCG, Serre ML, Christakos G, Leone PA, Miller WC. Spatial analysis and mapping of sexually transmitted diseases to optimise intervention and prevention strategies. Sex Transm Infect. 2004;80:294-299. • ArcPad—Mobile GIS software for field mapping applications. ESRI Web site. http://www.esri.com/software/arcgis/arcpad/. Accessed April 23, 2008. • Holmes EE. Basic epidemiological concepts in a spatial context. In: Tilman D, Kareiva P, eds. Spatial Ecology : The Role of Space in Population Dynamics and Interspecific Interactions. Princeton, NJ: Princeton University Press; 1997:111-136.