Fighting dengue fever with GIS
The National Environment Agency (NEA) in Singapore started deploying GIS in 1992 in order to develop a real-time Aedes mosquito control and monitoring system.
GIS is an automated computer-based monitoring tool with the ability to capture, retrieve, manage, display and analyse large quantities of data in a geographical context, through a series of maps “layered over” each other. The entire system is built on software, hardware, data and procedures. To put it simply, information received will be digitised in layers, then integrated for analysis.
Dengue fever is classified as a major international public health concern by the WHO. Why dengue fever made a comeback in Singapore is complex. However, one cause has been high rainfall and increased humidity. Hence, the use of GIS can help Singapore in dengue prevention and control, and in turn avert the spread to neighboring countries.
The NEA has five regional offices around Singapore doing control work. The intranet, located at the NEA headquarters, is the central transmission location where information is captured and disseminated to the five regional headquarters, IT manager Ginny Tan says.
Currently, the intranet is also linked to PDAs, which every health official doing routine checks for dengue has in hand. The device is used to input field surveillance data which is downloaded into a server and then read directly by GIS, Tan said.
The system has a base map layer that details every street, building, urban rail station, clinics, food centres and construction sites and so on. Further information such as patients’ particulars, location of breeding, larval densities and the type of aedes mosquito is mapped to form a comprehensive system.
The system is also able to provide information on how disease spreads, a process known as epidemiological analysis. For example, if a group of Muslims from the same mosque contract dengue fever, it is likely that there is a breeding ground at the mosque. Dengue cases can then be analysed with such environmental data.
The results are collated weekly and analysis is then done in order to identify hotspots or risk areas that may be impending breeding grounds. The breeding points would be sorted out by density and classified as a cluster if there are two or more cases of dengue located within a distance of 150m.
At the NEA, GIS map focus will be based on past trends, areas where the virus has not hit, vacant premises and population density data. The NEA also works with various meteorological stations to collect data which will be used to create a map detailing possible hotspots based on the weather conditions.
Benefits Director of Environmental Health Department Satish Appoo, says GIS provides almost immediate response speed, which is critical as a report needs to be quickly sent to regional offices. He added that he is “very satisfied with the system” because of the accuracy and reliability that it brings.
Previously, the dengue team at the NEA had to rely on paper map and pins to record various locations daily and the regular changes made it confusing and difficult to analyse information.
Also, the GIS ensures that health officials are more precise in defining problem areas. Besides that, GIS is able to gauge whether previous efforts to control the disease have been successful and corrective action can be done effectively.
However, in terms of cost, Satish said the system is “definitely not cheap” but the benefits they can leverage from the system far outweighs the cost and this is the reason they have been deploying GIS for the NEA since 1992.
Planned improvements As with any system, there are always further improvements that can be done to increase the performance level. The NEA is looking to connect their intranet with other government agencies and meteorological services so as to create a more concise system for immediate updates on issues and weather conditions. Also, the NEA hopes to be able to install the GIS on the PDA, which currently records only in text form.
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