Dengue control - Singaporean experience

Lionel Wijesiri

While I was debating myself the best way I could make use of my 24-hour short stop-over in Singapore recently, I was introduced to a local professional who had a thorough knowledge on Singapore’s campaign against the Dengue challenge. In fact, much later I came to know that he was involved in the program for over a decade.

For over three hours he explained to me the past, the present and the anticipated future of their Dengue Control program. Later, he took me around the City State showing me the operations. Listening to him, I thought “Maybe, we could learn few lessons from the Singaporean experience.”

Dengue has remained a challenge for highly urbanized Singapore. Picture daylife.com

Dengue, being an urban disease, has remained a challenge for highly urbanized Singapore. Since the 80’s, they have been experiencing cyclical outbreaks, which peak every five to six years, with baselines rising after each cycle. Singapore has an aggressive mosquito control program, which helps keep mosquito population and transmission rate low.

Unfortunately, their vector control efforts over the last three decades have also paradoxically resulted in a large segment of the population today having lower immunity against dengue. In 2005, they encountered their worst dengue outbreak ever, with more than 14,000 reported cases. It was a timely reminder that their battle against dengue is far from over, and they need to take another look at their dengue control regime in the face of new challenges.

Singapore has since refined her vector control program into one that integrates surveillance using field and laboratory data, as well as an evidence-based pre-emptive source reduction and outbreak-response regime. The close inter-sectoral collaboration, particularly between the Environment and Health authorities, has been the driving force in their surveillance and response. This symbiotic relationship has also been significantly strengthened following the last outbreak.

Having in-depth understanding of the vector, the disease and its transmission dynamics is critical to further refining our dengue control operations for optimal results. Hence, Singapore has in recent years placed greater emphasis on building their research capability, through the Environmental Health Institute under the National Environment Agency.

National Environmental Agency (NEA)

Singapore saw a dramatic decrease in the number of dengue cases in the first half this year. (See chart). Singaporean authorities are taking a more concerted approach in the fight against the mosquito-borne disease, which can be fatal in its severest form.

The National Environmental Agency is the main authority in charge of the Dengue Control Program. Its key strategy in dengue control is to tackle the root of the problem, which is to deny Aedes mosquitoes the place to breed (i.e. source reduction). They maintained the rigorous dengue control regime throughout which has helped to keep the incidence of dengue low in Singapore.

NEA adopts a multi-pronged approach to control dengue.

a. preventive surveillance and control;

b .public education & community involvement;

c. enforcement; and d. Research.

Preventive surveillance and control

NEA conducts daily mosquito surveillance operations. They use the daily data gathered during field surveillance and with the aid of the Geographical Information System. This information enables NEA to move quickly into areas to do source reduction (i.e. remove/destroy breeding grounds found). These are important steps to prevent possible dengue transmission.

NEA’s mosquito surveillance operations strategies are two-fold: (1) Active surveillance in areas prone to dengue and/or where there is high mosquito population, (2) Breaking the source of transmission as quickly as possible when cases (both suspected and confirmed) and clusters of cases emerge.

(a) NEA’s Pest control efforts

NEA has sufficient manpower deployment for mosquito control. It has formed dedicated local teams responsible for regular auditing, inspections and enforcement in each of the 84 constituencies. These teams, being familiar with the areas under their charge, are able to identify and pre-empt potential problematic areas quicker and more effectively.

(b) Integrated Efforts with Other Agencies/Organizations

NEA works with various land agencies as well as private organizations and associations to ensure that there is a coordinated approach in keeping the mosquito population and dengue cases low.

Construction sites. An Environmental Control Officer (ECO) Scheme had been introduced in construction sites. Under the Scheme, construction sites are required to engage a part time or full time ECO depending on the cost of the development. These NEA-trained ECOs are responsible for maintaining the pest and mosquito control works within the construction sites.

To be continued