Geographic Information System (GIS) as a Tool for Disease Surveillance and Environmental Health Research F. Benjamin Zhan, Yongmei Lu, Alberto Giordano, Elaine J. Hanford Texas Center for Geographic Information Science
Texas State University, San Marcos, TX 78666, USA
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[email protected] Abstract- While we have seen the wide use of other information technologies in health services and management, the use of geographic information technologies in health related services has been limited so far. Given that location-related data play important roles in many health related services, it is anticipated that geographic information technologies have a lot to offer in helping improve health related services, management, and research. As an example, the authors report the development of a geographic information system (GIS) for Texas-Mexico border disease surveillance and environmental health research. This presentation covers three important aspects in the development of the GIS: (1) the specification of uses and usem of the GIs and the associated data, products, and functions; (2) a preliminary design of the data types and formats in the GIS; and (3) a prototype of a GIS-based spatial search tool that can be used to support environmental epidemiology research. In some disease monitoring and environmental epidemiology studies, it k often necessary to perform spatial search to determine the distances between environmental hazardous sites and the locations of cases and controls when distance is used as measure of exposure. The GIS can be used to interactivety and automatically determine the distance between any possible pair of environmental hazardous sites and casdcontrols. Preliminary results suggest that the prototype GIS is indeed a powerful tool for spatial search when distance is used as a measure of exposure in environmental health research. The reported system should be useful to researchers facing similar situations in disease monitoring and environmental hedth research. . Keywords: GIS; Spatial Analysis; Environmental Health; Epidemiology; Disease Surveillance
I. INTRODUCTION The overall objective of this research project is to establish a geographic information system (GIS) to actively identify and monitor the movement of disease back and forth across the Texas-Mexico border and to facilitate environmental health research on the development and spread of drug-resistant disease and proliferation of vector-borne disease in a timely and effective manner. This surveillance system will require an estimation of the population in the border region and community-level migration rates across the border including normal population migration and, in particular, an estimation of the movement of migratory and seasonal workers with respect to vector-borne diseases and drug-resistant diseases. Further, consideration was given to specific characteristics of reportable diseases and how a surveillance system could be developed based on user needs and the characteristics of the
diseases. Development of a surveillance system using geographic information system (GIs) emphasized the need to increase public participation in surveillance, the type of data and format to be employed in surveillance, the expected productshnformation and functionalities of the system. Specifications of the U.S. Centers for Diseases Control (CDC) National Electronic Disease Surveillance System (NEDSS) [l] were used as a starting point and extended to accommodate the diseases common to the Texas-Mexico Border and include critical geospatial components in the system. 11. RELATED WORK
A systematic review and assessment of published studies on diseases and disease surveillance systems in the context of migrating people and disease movement, vector-borne diseases, and drug-resistant diseases was conducted with particular emphasis on the Texas-Mexico Border Region. To focus on reliable and temporally relevant infomation, the literature search was focused on material published since 1990 and included literature sources, articles, documents and data identified using electronic searches of national databases and electronic resources publicly available through the State and federal agencies. References were selected to provide background information on the Texas-Mexico Border Region, the etiology of diseases of concern, and border disease surveillance systems. A. Migrating People and Disease Movement
It is generally recognized that various ethnic-immigrant and US-born groups differ in their risks of all-cause and cause-specific mortality, morbidity, and health behaviors [2], [3]. Along the US-Mexico border region, substantial nativity differences in health status and mortality of immigrant and migrating people is focused primarily on those of Hispanic ethnicity born in Mexico [4], [ 5 ] . In particular, concerns relating to health along the border mdst recognize those persons immigrating, those traveling for business or personal reasons, and those persons who cross the border region for occupational reasons and include the migrant and seasonal farmworkers and their families [6]. The numbers of such migrant persons is not well-documented [7]. Villarejo [SI notes that little is known about the health of this migrant population. The uncertainty of the numbers of such migrants, their locations of origin, and the pathways of migration poses
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including El Paso and Houston, Texas. At present, the clinical data being entered into the RODS system comprise de-identified emergency department visit abstracts to monitor for anomalous patterns or increases in numbers of patients with symptoms of flu, respiratory illnesses, diarrhea, and skin B. Diseases of Concern rashes 1111. National Retail Data Monitor ( N W ) is a The list of Texas Department of State Health Services surveillancesystem aimed at early identification of outbreaks (TDSHS) notifiable conditions was used as astarting point to of diseases by monitoring the sales of over-the-counter tabulate specific disease characteristics (incubation period, healthcare products [I 1]-[13]. communicability, causation and relationship to the border) to With the support of CDC,the Public Health Information consider how these diseases would affect the development of Network (PHW) is designed as a network to consistently a surveillance system. In general, these diseases include exchange health and disease tracking data as well as response those that are communicable, are vector-borne, and are strategies between public health partners. The National transmitted by consumption of contaminated food or water. Electric Disease Surveillance System (NEDSS) is a major component of PHIN.The purpose of NEDSS is to “promote(s) C. GIs and Vector-Bonze Diseases the use of data and information system standards to advance There is extensive literature on the etiology of these the development of efficient, integrated, and interoperable diseases, with a number of workers investigating their surveillance systems at federal, state and local levels” Occurrence in the Americas using Geographic Information (http://www.cdc.gov/nedss/). This surveillance system is Systems (GIs). For example, Kavni and Usery [9] provide designed to enhance the national ability to identify and track an overview of the application of remote sensing and GIS for as early as possible emerging infectious diseases and monitor monitoring of vector-borne diseases. Peterson and others [ 101 disease trends. As an early implementation of NEDSS, a used ecologic niche modeling (remote sensing & GIS NEDSS Base System was designed and is the most application) of packrats to evaluate potential for commonly adopted system at the state level, including such vector-parasite reservoir distribution for Triatoma species states as California, Louisiana, Minnesota, North Carolina, implicated in transmission of Chagas Disease and confirmed Oregon, Pennsylvania, Utah, and Texas. two regions where it had been predicted but not previously One important feature of NEDSS is that it is designed as a collected. Ecological modeling using GIS may help in standard for disease and health data to be electrically identifying disease risk areas, planning vector-control transferred over the Internet from health care providers to strategies, and exploring parasite-reservoir associations for health departments (state or national level) for the purpose of other emerging diseases. diseases detection and monitoring to broadly protect the D. Disease SurveiZlance Systems public health. As such, NEDSS lacks necessary specifications A surveillance system can serve as an important means to for a surveillance system for the infectious and vector-borne monitor (communicable) diseases. An effective surveillance diseases specific to the Texas-Mexico border region for two system provides information regarding the outbreak, reasons, First, the diseases of concern along the border region distribution and controls of (communicable) disease of might not be treated properly by NEDSS. Second, the special significant concern €or public health and environmental nature of trans-border movement of population and its effect health research. Moreover, a surveillance system should have on the monitoring and spreading of diseases may not be the function of issuing early warning signals regarding the addressed by the design of NEDSS, but are critical for the possibility of outbreak or reemergence of disease so that effectiveness of this border health surveillance system. The need for a surveillance system to monitor diseases appropriate medical or administrative intervention can be along the US-Mexico border has long been recognized. The implemented in a timely manner to prevent epidemics. Surveillance systems have been widely recognized as an “Border Infectious Diseases SurveillanceProject” (BIDS) is a important and effective means for public health management. binational U.S.-Mexico initiative established by four The Global Public Health Intelligence Network (GPHIN) is a American and six Mexican border states with support from second generation electronic surveillance system developed the respective federal governments and the Pan-American and maintained by Health Canada with restricted Health Organization (PAHO).Weinberg and others (2003) (pre-approved) access limited to a number of public health presents an overview of BIDS. In 1993, the then Texas Department of Health (renamed as organizationslprofessionals. At the local and national levels, there are existing surveillance systems for communicable the Texas Department of State Health Services (TDSHS) in diseases. The Real-time Outbreak and Disease Surveillance 2004) created its own Office of Border Health (OBH) to (RODS) software developed by the University of Pittsburgh include community sanitation, food and product safety, is an open-source public health surveillance software package. environmental health survey, data infrastructure and RODS was utilized by the Utah Department of Health during collaborationlcoordination. Both BIDS and OBH stress the the 2002 Winter Olympics and is being utilized by health care importance of involving a wide range of users in the U.S. and facilities and agencies in a number of states and cities, Mexico, including the population at large which has been
a difficult problem in real-time surveillance and mapping of such persons and health-related conditions, as well as conducting environmental health research within this population.
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deemed crucial to ensure the success of the programs [Id]. In other similar and related efforts, Balk, Golden and Iwaniec [15] presented an interactive system for mapping data, including socio-demographics at the county or municipal level. Foldy and others [16] demonstrated a short-term real-time coordinated surveillance and communication tool by using an existing secure regional Internet infrastructure and drop-in systems; this system is limited because it relies on manual data collection.
III. USER EXPECTATIONS
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A. NEDSS and the Texas-Mexico Surveillance System NEDSS is a federal initiative for the development of disease surveillance systems at the national, state, and local levels. NEDSS includes data standards, data models, and system architecture specifications and is designed to be integrated with the existing national Health Level 7 (HL7) standard for the electronic data exchange of health data. A main component of NEDSS is a standard for the electronic transfer of information from health care systems (e.g., hospitals) to health departments over the Internet. NEDSS also defines protocols and procedures for the dissemination of health information to primary care physicians, public health workers, and emergency response officials. NEDSS identifies a wide range of users of health information specifically related to disease surveillance. In doing so, it provides the logical framework for any kind of border health surveillance initiative, including the Texas-Mexico Border Disease Surveillance System. The starting point of the framework is the NEDSS Base System. According to CDC, which devised NEDSS, the Base System is an example of a NEDSScompatible system that can be used by a state health department for the surveillance and analysis of notifiable diseases. As such, it provides a platform upon which modules
can be built to meet state and program area data needs as well as providing a secure, accurate and efficient way for collecting and processing data. The NEDSS Base System thus allows states to tailor NEDSS to their specific circumstances and diseases of concern. In general, the main difference between states concerns the diseases to be reported. These vary based on specific human, environmental, and geographical characteristics. The reporting modalities also vary by disease. The functions and activities of the Texas implementation of NEDSS are similar to those of other states, with a specific focus on issues of data quality, case investigation, and quantitative analysis of data.
B. Selected Diseases and Assessment of GIs Functionalities In NEDSS, Business Groups define a typology of users and uses of the systems (see www.cdc.gov/nedss/BaseSystem /BusinessProcessGroups.pdf) - surveillance and intervention program management, person surveillance, population surveillance, population intervention, analysis, visualization and reporting, and notification. This generalized view of the
users and uses of a surveillance system -- adapted for the Texas-Mexico border disease surveillance system -- can be progressively refined with respect to user needs and GIS functionalities for specific diseases. In general, the creation of a GIS-based Texas-Mexico border surveillance system must address several critical design challenges. Some of the challenges stem from the characteristicsand functions of the Business Groups involved in disease surveillance and intervention. First, since procedures are defined for both active and passive surveillance, a wide range of functionalities will be required of the GIs, including online and real-time capabilities; this will require heavy customization of existing GIS hardware and software. Second, since data collected at the individual level need to be aggregated and analyzed a! the population level, appropriate spatial analytical tools need to be selected and implemented in the GIS; this will require at least basic training in GIS and spatial analysis for a wide range of users, including epidemiologists and other specialized health officials at various levels. Third, the range of users of the system will require the design and implementation of appropriate visualization techniques tailored to the backgrounds and expectations of different users. Fourth, since one of the principal methods of GIS-based information dissemination will be a website, careful consideration must be given to the design of the site to ensure access and confidentiality appropriate to the types of data and information collected, analytical options, and generated results. Fifth, possibly the most crucial obstacle to overcome will be how to integrate two disciplinary cultures: epidemiologists and GIS specialists. Epidemiologists and other specialized officials will need to understand and be trained in how GIS works and to familiarize themselves with basic spatial analytical techniques, including the limitations
and shortcomings of the technology and the techniques. On the other hand, GIS technical personnel (at least at more senior levels) will need to have at least a basic knowledge of epidemiology and to be familiar with field data collection procedures.
C. Summary Comments on Users and Uses On the basis of the analysis, a few general recommendations can be provided concerning the most critical aspects of the design of the GIs-based surveillance system to ensure the success of the initiative: Because the system requires both active and passive disease surveillance capabilities, the GIS will need to be customized. Out-of-the-box solutions are not a feasible option, particularly for users in Population Intervention and (especially) Analysis, Visualization and Reporting. These users integrate the spatial analysis capabilities of GIS with the epidemiological modeling functionalities of the surveillance system: they will therefore need specialized training in both fields. The system will need online and real-time capabilities for disease monitoring, surveillance, and
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management, and for information dissemination and public warning (if applicable). Because different diseases are managed differently, GIS functionalities need to be designed specifically to reflect these differences, especially the study of the spatial extent and spatial diffusion modalities of various diseases and the specific characteristics of each disease (e.g., speed of diffusion, degree of communicability, and virulence). 3) Extreme care must be taken to ensure epidemiologists and other relevant health care professionals, especially in Population Intervention and Analysis, Visualization and Reporting receive at least basic training in spatial analytical techniques and geographic information science. Conversely, geographic information scientists must be trained so that they understand basic epidemiological issues. Because the system has the potential to respond to the needs of a wide range of users -- ranging from the general public to decision makers and politicians, from health care professionals in the field to state epidemiologists -- it is imperative that the interface of the system be designed to accommodate the various users, their function in the surveillance system, background, and need-to-know basis. The information provided by the system must be visualized as appropriate for the needs of each user group. A generic interface that is not tailored to a specific group of users and uses must be avoided. In addition, a system should not require the public or members of Surveillance and Intervention Program Management and Person Surveillance to learn GIS principles, query modalities, or software. These potential limitations can be minimized by a sound implementation of the system based on geovisualization and web design principles.
IV. DATA TYPES AND FORMATS The Texas-Mexico border disease surveillance system has a number of special characteristics: This is a surveillance system that can be used to collect; store, analyze and visualize information about communicable diseases, their distributions, and their spatial-temporal patterns in the border region. This surveillance system is accessible to all parties who have interests in issues related to border community health, including health care providers, health departments at the federal, state and local level, health problem analysts, and the public. For different groups of users, the surveillance system will provide different levels of accessibility and functionality so that their specific needs such as reporting, query, analyzing, or mapping can all be met. This surveillance system will be built on technologies that include the Internet, geographic information systems (GIs), and spatial statistics. It will be used to collect and distribute information through the Intemet
5)
while storing and Oanalyzing information using GIS and spatid analysis methods. This surveillance system is designed especially to collect and analyze information about diseases along the Texas-Mexico border (but could be extended to other types of diseases or regions when needed). It will have special features to record and analyze patterns of migrating workers, disease vectors, and drug resistance diseases that are of special importance for the border region.
A. Architecture
To enable the collection, management, analysis, and distribution of disease-related information, the Texas-Mexico border disease surveillance system integrates three types of technologies: the Internet, GIs, and geospatial analysis methods. This system will be used by different groups of users with different levels of accessibility and functionality requirements. For these purposes, this surveillance system will have different components that focus on different aspects of the functions; it will also have different features and levels of accessibility designed for different groups of users. The components of the proposed surveillance system and the functionality of each of the components of the system are described below. Data collection component: This system will allow for reporting of cases from health care providers and related clinical labs, as well as the public if applicable. This surveillance system will emphasize the spatial location and migrating patterns of related cases and populations during the incubation, sick, and recovery period of individual patients. Data management component: The reported cases will be stored and archived in the database management system (DBMS) ready for query and analysis. Data security will be implemented for privacy issues while providing appropriate access level for respective user groups. This group functionality will be handled by an “Internet-savvy data server.” In addition to a DBMS, a “data request interpreter and processor” and a “GIS gateway” will be included in this component. The former wil1 process and classify requests for data and analysis. For certain basic requests, the data server will call for a “GIS gateway”, which can perform basic analysis and mapping and can pass the result directly to the “Data reporting and visualization” component. Data analysis component: This group of functions will be based on GIS and spatiotemporal analysis techniques. They will be designed to provide all users with effective analysis and query power, while keeping the application as efficient as possible and avoiding waste of resources. For this purpose, three levels of functionality will be included in the system; the “Data analysis component” will be invoked by an “Internet Savvy Data Server”, which has a “Request interpreter & processor” and can process requests for
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data and analysis and further make savvy decisions regarding which level of functionality to call for. The data analysis component will integrate three levels of GIS functionality architecture [ 171: static access query and display for basic level access (such as the public), interactive access information query for intermediate level query (such as health care providers and police makers), and comprehensive and intelligent access analysis for the most advanced user group (such as public health analysts and researchers). 4) Data reporting and visualizing component: This part of the system combines information distribution technology from the Internet and mapping and visualization technology from GIs. It provides reports using tables, maps, and graphics from the basic information leading to conclusions regarding outbreak, spreading, migrating, or re-emergence of diseases of concem in the Texas-Mexico border region. It provides the options of both web-based reporting and downloadable reports and maps.
B. Data Model, Data Type and Data Format Several types of information are going to be collected, stored, and analyzed in the Texas-Mexico border disease surveillance system. The type of entities being described and the attributes of each entity must be recorded in a specific data format. Although primarily related to the “Internet-savvy data server” component described above, the data and format employed in this system will also support the operation of other components of the system. There are several existing disease surveillance systems. However, none of the existing systems are designed to (1) monitor and detect the outbreak and spread of diseases of special concern to the Texas-Mexico border region in the context of this project, and (2) track the impact of migrating workers across the border relative to the outbreak and spread of diseases. For the Texas-Mexico border disease surveillance system, we will take into consideration both the specific diseases and the relationship between the spread of a disease and the specific nature of migration patterns of farm workers. The border disease surveillance system will build upon the existing surveillance systems, especially NEDSS, by modifying them to address the concerns of outbreak and spread of disease dong the Texas-Mexico border. C. Evaluation of the Current Disease Reporting Forms
Review of current requirements for notification and the forms currently in use for notification for these diseases revealed that they do not necessarily include information critical to describing and analyzing the spatial origination, Occurrence and spreading of disease within an active GIs-based surveillance system. Geospatially related data/information may facilitate delineating where a patient was exposed to disease vectors. However, to develop a more comprehensive assessment of where the patient may have been exposed, information relating to employment address
and other daily activity locations should also be collected. In addition, specific format of address information and information related to travel history during incubation period {paths, destinations, etc.), as well as donating or receiving of blood I blood product I organ I tissue during the incubation period should be collected in a more rigorous way to insure the accuracy of information for geocoding and geospatial analysis. In particular, for diseases for which various viral serotypes are recognized, reporting should include identification of the virus serotype for mapping not only the incidence and spread of the disease, but of the individual serotypes that pose varying risks to humans. Disease which has an extremely long latent stage may pose the most difficulty in identification of outbreaks, mode of transmission and geographic location of exposure, as well as the migration paths of those infected. Relevant diagnostic and geospatial data become more critical to determining the source and spread of such diseases. For diseases which are highly communicable, location information about the moving path of a patient (including past and current residence and working places as well as travel) during the incubation period as well as during the time a patient is sick is critical for the following reasons: 1)
To be able to trace back following the moving path of a patient the possible cases of tuberculosis at the early stage for disease development;
To be able to geospatially (and temporarily) link related tuberculosis cases and identify the most dangerous “node” of disease spread; 3) To be able to target more susceptible population for preventive practice. For food- and water-borne diseases, basic information on treatment might not be as important, but geospatial information is still critical for understanding the outbreak and spread of the disease. Information about the patient migration path during the incubation period and illness should be collected in as much detail as possible. 2)
V. SUMMARY A preIiminary analysis of uses and users of the Texas-Mexico Border Disease Surveillance System suggests that the concept of seven Business Groups as identified in NEDSS and the disease reporting procedures used by the Texas Department of State Health Services (TDSHS) should be adopted for the development of the system. In particular, the following recommendations are deemed important: (1) Categorize all users of the system into seven different groups -- surveillance and intervention program management, person surveillance, person intervention, population surveillance, population intervention, analysis, visualization and reporting, and notification; (2) Because the system requires both active and passive disease surveillance capabilities, the Geographic Information System (GIS) component of the system will need to be customized to facilitate different users and user groups; (3) The system will need to be designed and developed in
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such a way that it provides online and real-time capabilities for disease monitoring, surveillance, and management, and for information dissemination and public warning. In studying the data types and formats for disease reporting, it has been determined that the forms currently in use by the Texas Department of State Health Services (TDSHS)can be used as the basis for disease reporting. But these forms are mainly designed for medical practice and basic reporting for passive surveillance and these forms need to be revised to include more detailed geospatial data for the purpose of active surveillance of diseases. Geospatial data for patients, such as the locations of their activities, their daily routes, and their migrating paths during the incubation period as well as the sick and latent periods of a disease should be collected. These data items should be added to the forms. The geospatial data are critical for the surveillance system to track the source and spreading paths of a disease so that early detection of a potential outbreak of a disease becomes possible. In addition, accurate and detailed geospatial information would also help health officials to deploy limited resources to target the most vulnerable areas and protect the population at highest risk.
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ACKNOWLEDGMENT Effort reported in this paper is sponsored in part by the 31 1” Human Systems Wing under Partnership Intermediary PIA FA8901-04-3-5O00, The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the U.S. Air Force or the U.S. Government.
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