He took out his personal digital assistant, and almost instantaneously, a central computer in National Environment Agency (NEA) headquarters had taken note of the new breeding site.

Together with information about other dengue cases, including other breeding sites, the new information could give important clues as to how victims in the cluster are infected. Dengue is actively transmitted in the area, with 17 cases since the cluster was identified.

The information, which all five NEA regional offices have access to, could also point to new possible infections, prompting immediate preventive action.

This is possible thanks to a high-tech Geographical Information System (GIS), another weapon in the NEA's arsenal in the fight against dengue, said Mr Tai Ji Choong, head (operations) of the Environmental Health Department.

The GIS allows the NEA to map out everything from outbreaks and complaints to actual breeding sites over both space and time.

Explained Mr S. Satish Appoo, the department's director: 'In the past, it would have been a wall map with push pins. We would send out the information and they would have to map it out manually.'

The current GIS system has been in operation since 2001, and builds on software the NEA has used since the 1990s. It gives instant information on how problem spots develop, for example, so the NEA can take immediate action.

At 4pm each day, the Health Ministry gives the NEA the figures, including information about new dengue cases. The numbers go into the system, and the next morning, NEA officers are on site combing the area.

It is not unlike a battleplan, against an enemy that has already killed two people this year.

Last week, there were 349 cases, a dip below the official epidemic level, but still uncomfortably high. Since Sunday alone, the tally has already reached 147.

The system helps to identify developing clusters, and indicates places where people congregate, such as food centres, which should be scoured for breeding sites.

It also highlights construction sites and vacant premises, which can be targeted in checks, and identifies general practitioners so those in outbreak zones can be put on high alert.

The system can even show where a dengue patient works or studies, potentially identifying other places where the Aedes aegypti is active.

The potential spread of disease outside a current outbreak zone can also be tracked.

For example, in attempting to contain a former cluster in Little India, cases seemed to spread from Veerasamy Road towards Race Course Road. The NEA moved into the nearby Boon Keng area before it went further, diverting more men to search and destroy breeding sites and warn residents.

In the past decade, the NEA has also tracked the exposure level of various areas to each type of dengue - Den 1, 2, 3 or 4. In this way, it hopes to learn which areas have lowest immunity to the currently dominant type. That process helped identify the 44 priority areas where the NEA has concentrated resources during this outbreak.

'It's a real improvement in efficiency... and has allowed us to respond faster than ever before,' said Mr Appoo.

arti@sph.com.sg

To see a hands-on demo of the system, catch our free video report.