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GIS: A tool for monitoring and management of epidemics
Advantages of GIS
GIS has several advantages over conventional methods used in health planning, management and research. Data management: GIS can be used to capture, store, handle and geographically integrate large amounts of information from different sources, programmes and sectors; including epidemiological surveillance, census, environment and others. Surveillance of diseases requires continuous and systematic collection and analysis of data. A GIS can eliminate the duplication of effort involved in data collection across an organisation, and hence substantially reduce the cost involved in it. GIS serves as a common platform for convergence of multi-disease surveillance activities. Each data record has to be georefenced to a desired level of accuracy. Standardised geo-referencing of epidemiological data facilitates structured approaches to data management (Weekly Epidemiological Record, 1999). Once the basic structure is ready, it is easy to convert it to surveillance system for any other disease, by replacing data of one disease with data of another disease (Srivastava & Nagpal, 2000).
GIS provides access to additional information from a wide variety of sources. Global positioning systems (GPS) can be used to obtain locations of point features on a map, such as wells or septic tanks, precisely. GIS can process aerial or satellite imageries to allow information such as temperature, soil types and landuse to be easily integrated, and spatial correlations between potential risk factors and the occurrence of diseases to be determined (Weekly Epidemiological Record, 1999). High resolution satellite imageries and aerial photographs can be used to obtain accurate and up-to-date maps of any region. Latest, accurate, low-cast maps are essential for epidemiological surveillance. Temporal satellite imageries can be used to monitor landuse and landcover changes over time.
Visualisation:
GIS offers powerful tools to present spatial information to the level of individual occurrence, and conduct predictive modelling. It determines geographical distribution and variation of diseases, and their prevalence and incidence. For example, in studying the surveillance of poliomyelitis in India, it is important to find out which type of polio is occurring in which parts of the country, as this has important implications for the disease eradication strategy employed (Balaji, 2000). GIS can help in generating thematic maps - ranged colour maps or proportional symbol maps to denote the intensity of a disease or a vector. In comparison with tables and charts, maps developed using GIS can be extremely effective means for communicating messages clearly even to those who are not familiar with technology. GIS keeps track of the geographical locations of service providers, customers, resources, and health plans and programmes. It allows policy makers to easily understand and visualise the problems in relation to the resources, and effectively target resources to those communities in need. GIS permits dynamic link between databases and maps so that data updates are automatically reflected on the maps.
Overlay analysis:
GIS can overlay different pieces of information. This helps in decision making and medical research through multicriteria modelling (for example, in understanding the association between prevalence of certain diseases and specific geographic features).
Buffer analysis:
GIS can create buffer zones around selected features. For example, a radius of 10 km around a hospital to depict its catchment area or 1 km around a pollution site or 5 m on both sides of sewerage to indicate the spread of hazardous material. The user can specify the size of the buffer and then combine this information with disease incidence data to determine how many cases fall within the buffer. Buffer or proximity analysis can be used to map the impact zones of vector breeding sites, where control activity needs to be strengthened (Srivastava & Nagpal, 2000).
Network analysis:
GIS provides the ability to quickly access the geodemographic dynamics of an organisation's existing service area in contrast to the likely demand for services at a new location (ESRI White Paper, 1999). It can identify catchment areas of health centres and also locate suitable site for a new health facility. Health services delivered at home (e.g. polio vaccination) can be scheduled in a more efficient manner by analysing transportation factors and street patterns, and by recommending the most efficient route. GIS Provides accurate and timely information about where health services are located and instructions and maps on how to get there.
Statistical analysis:
GIS can carry out specific calculations, for example, proportion of population falling within a certain radius of a health centre or dam. It can also calculate distances and areas, for example, distance of a community to a health centre, and area covered by a particular health programme.
Query:
GIS allows interactive queries for extracting information contained within the map, table or graph. It can answer queries of location, condition, trends, spatial patterns and modelling.
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