Our integrated dengue surveillance and control programme has been put in place since the 2005 dengue outbreak in Singapore, and is in line with the World Health Organization (WHO)’s recommendations. NEA has also been commended by WHO for its effective control of the Zika outbreak in Singapore in 2016.

The key strategy for dengue control is source reduction – the detection and removal of mosquito breeding habitats and mosquito larvae/pupae. Besides conducting checks for mosquito breeding habitats based on dengue cases, we also take a preventive and risk-based approach through pre-emptive checks in areas assessed to be at higher risk, even in the absence of dengue cases. This helps to eradicate mosquito breeding habitats (source reduction) and suppress the mosquito population, such that dengue transmission cannot be sustained. In areas with intensified dengue transmission, NEA works closely with members of the Inter-Agency Dengue Task Force (IADTF), such as PUB, NParks, HDB and Town Councils, to ensure that mosquito control measures are carried out and sustained in the respective areas under their care.

NEA takes a multi-pronged approach to dengue control, comprising vector control measures, stakeholder engagement, as well as community mobilisation and public communications. Our strategies for controlling dengue include:

• Surveillance of the Aedes mosquito population with Gravitraps, which enables NEA to conduct more targeted and effective inspections, and vector control operations.
• Removing mosquito breeding sources through intensive indoor and outdoor search-and-destroy operations, and application of larvicide where necessary.
• Killing adult mosquitoes, including uninfected ones, through common measures such as insecticidal fogging and misting for outdoor areas, as well as space-spraying indoors. [These control methods are applied judiciously in situations where there is active disease transmission, to prevent build-up of insecticide resistance through unregulated use.]
• Risk communications and rallying the community/stakeholders to help sustain efforts for dengue prevention, by encouraging everyone to Do the Mozzie Wipeout and remove stagnant water. For example, NEA displays colour-coded alert banners at dengue cluster areas, and information on dengue cases, dengue clusters, and areas with high Aedes aegypti mosquito population, can be found on the NEA website. By making such data public, we hope to encourage members of the public to take on a more proactive role in dengue prevention, by checking their homes for possible mosquito breeding habitats and removing them.
• Legislation in the form of the Control of Vectors and Pesticides Act (CVPA), which penalises owners of premises and occupants for creating habitats favourable for mosquito breeding.

In spite of all our efforts, Singapore remains vulnerable to dengue for a few reasons:

• Dengue cases have been increasing globally. The number of dengue cases reported to the World Health Organization (WHO) has increased more than 15 fold over the last two decades, from 505,430 cases in 2000, to over 3,312,040 in 2015. The highest number of dengue cases reported globally was in 2019, with all regions affected.
• Being an international transport hub, Singapore is vulnerable.
• Singapore is in a dengue-endemic region, and there are four different Dengue virus serotypes (DENV-1, -2, -3 and -4) circulating concurrently. Historically, a change in the predominant virus serotype is usually associated with a spike in dengue cases.
• Our region’s constantly warm climate and high humidity allow the Aedes mosquitoes to breed all year round. The warm climate also supports faster multiplication of the Aedes mosquito vector and the Dengue virus, contributing to more mosquitoes and more disease transmission.
• Our high human population density also aids the breeding of the Aedes aegypti mosquito. This species has adapted particularly well to our urban environment, because it likes to breed, mate and feed near human dwellings.

NEA continues to explore new tools and technologies to complement its existing mosquito control measures. NEA’s Environmental Health Institute (EHI) has studied various novel mosquito control methods since 2010, and has focused on the Wolbachia technology since 2012. ‘Project Wolbachia – Singapore’ has achieved more than 90 per cent suppression of the urban Aedes aegypti mosquito population at study sites at Yishun and Tampines towns, and has kept these mosquito populations at low dengue-risk levels for more than a year. In May 2020, NEA expanded the releases of male Wolbachia-carrying Aedes aegypti (Wolbachia-Aedes) mosquitoes to selected dengue high-risk neighbourhoods at Choa Chu Kang, Keat Hong and Hong Kah North, which have high urban Aedes aegypti mosquito populations.

Meanwhile, community vigilance and action remain critical in our fight against dengue and other diseases such as Zika. NEA cannot control dengue alone. All stakeholders must continue to do their part to help stem dengue transmission in the environment and reduce the mosquito population, by checking their premises daily for potential mosquito breeding habitats and removing them.