Monday, April 21, 2008

Mapping places at risk of dengue in Malaysia

IMAGINE opening a map and immediately being able to identify the area where a dengue outbreak is going to occur.

Now imagine doing this monthly and preventing an outbreak.

This would be the reality next year if Malaysian Remote Sensing Agency director-general Darus Ahmad has his way. Preferring to focus on prevention rather than the cure, Darus came up with the idea of using remote sensing technology to come up with a dengue risk map.

“The idea came about when we realised that current approaches are only used to address the issue after it had already happened. So we thought of preventing it before it happened by narrowing down the likely areas to be affected before the dengue outbreak even occur red,” Darus said.

The map, which is expected to be ready by the end of the year, would identify dengue “hot-spots” on a monthly basis.

The map will also be able to identify areas which are not dengue-prone in the past but may be in the future.

It will also show the exact locations and the severity of dengue outbreaks. In addition, the map will also be able to identify activities which contribute to the presence of Aedes mosquitoes.

“For example, we found that the number of dengue cases was lower in areas with bungalow houses than those with terrace houses,” Darus said.

The dengue risk map pilot project started in 2005 and covered the area of Subang Jaya . It was jointly conducted by the Malaysian Remote Sensing Agency, Institute for Medical Research and the Subang Jaya Municipal Council.

Subang Jaya was chosen for the pilot project because it was among the areas with the highest number of dengue cases.

The pilot project involved drawing up dengue risk maps for the years 2002 and 2005.

To test the veracity of the maps, they were compared with the incidence of dengue outbreaks in those two years.

As the maps proved to be accurate, it was decided a risk map for 2009 would be drawn up.

The 2009 dengue risk map identified Seri Kembangan and USJ11 as areas with the most severe probable incidence of dengue. It also found that 20 per cent of the 437,121 square kilometres area studied was in the “very high risk” category for dengue outbreaks.

“Some of the areas in this category have no dengue cases at the moment but have a high probability of having dengue outbreaks in the future. We use satellites to monitor physical parameters or factors that affect the population of Aedes mosquitoes."

“This is then related to weather factors and ground data provided by the Health Ministry.We then map out the potential dengue risk areas.” The satellites are used to measure land use changes and its patterns, types of housing, land surface temperatures, land surface elevation and population density.

Weather patterns would also be included as one of the measurements in the future, said Darus.

“I hope the dengue risk map will help lead to better prevention methods.” Once the pilot project map is ready, he plans to roll it out nationwide and make the map available to the public.

“If the public are aware of the high-risk areas, they will most likely be more co-operative and more responsive to government advice.” Darus said the process of coming up with the risk map had also resulted in some interesting findings.

“We found that most dengue cases happened near construction sites and industrial areas. Interestingly, the areas with the highest number of dengue cases have mostly terrace houses.

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