SINGAPORE: The number of dengue cases in Singapore is down and most dengue clusters are no longer classified as hotspots, said Minister for the Environment and Water Resources Masagos Zulkifli on Monday (Sep 2).
Speaking in Parliament, Mr Masagos noted that as of Aug 24, the National Environment Agency (NEA) has closed 863 of 1,021 clusters formed in 2019, and brought down the number of dengue cases from a weekly high of 664 in mid-July to 478 in the third week of August.
The largest clusters in Woodlands, Upper Thomson, Chai Chee and Pasir Ris are among those that have closed, he added.
The surge in dengue cases this year is due to three factors: An increase in the mosquito population, warmer weather and lower herd immunity, he said.
To combat this, NEA has increased "housekeeping measures" and its inspections of common areas to eliminate potential breeding areas.
“In the first six months of the year, NEA conducted more than 442,000 inspections islandwide and uncovered about 8,200 mosquito breeding habitats,” said Mr Masagos.
"Sixty per cent of the breeding habitats detected were found in residential premises. In dengue clusters, the proportion of breeding habitats detected in residential premises is even higher at 70 per cent."
Between January and June this year, about 1,200 households were fined for mosquito breeding, he added.
Mr Masagos also said that mayors, grassroots advisers, community leaders and dengue prevention volunteers have stepped up public education campaigns, which contributed to the drop in dengue clusters and dengue cases from its peak in July.
NEA also started working with the People’s Association (PA) on Aug 25 to increase dengue outreach efforts, he added.
“Five thousand volunteers from PA grassroots organisations and Community Emergency and Response Team will work hand-in-hand with dengue prevention volunteers to conduct house visits and distribute dengue prevention leaflets,” said Mr Masagos.
OTHER INITIATIVES AND RESOURCES
NEA will also deploy 14,000 more Gravitraps to new Housing Board blocks and landed estates.
First introduced in 2017, there are currently 50,000 Gravitraps – which attract and trap female Aedes mosquitoes looking for sites to lay their eggs – across Singapore.
“The Gravitrap surveillance system allows NEA to prioritise its resources and deploy officers to focus on areas with high mosquito population,” said Mr Masagos.
Other than Gravitraps, NEA also publishes on its website information on areas with relatively higher Aedes aegypti adult mosquitoes “to facilitate targeted action by key stakeholders, community partners and resident”, said Mr Masagos.
“This information aims to increase awareness of dengue risk in areas with high mosquito population which might not yet be dengue clusters, so that stakeholders can pre-emptively take measures to reduce potential mosquito breeding habitats and avoid the formation of new dengue clusters.”
Mr Masagos also provided updates on Project Wolbachia. It involves infecting male Aedes mosquitoes with Wolbachia bacteria, so that when they mate with female Aedes mosquitoes, the female’s eggs do not hatch. Wolbachia-infected male mosquitoes also do not bite.
While studies have "shown promise", the Wolbachia technology has only been tested in small study sites in Singapore, he said, adding that NEA has to evaluate it "rigorously" before deploying it on a larger scale.
“The project is now in Phase 3, which aims to determine if the Aedes aegypti population suppression achieved thus far can be sustained in larger areas,” Mr Masagos said.
The release area currently covers 84 blocks in Yishun and 60 blocks in Tampines, and is 3.7 times larger than the initial release area for project Wolbachia.
However, Mr Masagos cautioned that the Wolbachia method is not a “silver bullet”.
“It will not replace the community’s efforts to ensure good house-keeping, which is still needed to keep our homes and estates free from mosquitoes and dengue," he said.
“Comprehensive mosquito surveillance, source eradication of mosquito breeding habitats, and spraying of insecticide where necessary to control the adult mosquito population, continue to be Singapore’s key strategies for dengue prevent and control.”