New visual reminders at areas with persistently high Aedes aegypti mosquito population will help to nudge key stakeholders, community partners and residents to take necessary preventive measures against dengue
Singapore, 10 March 2022 – Weekly reported dengue cases are rising sharply, with 264 cases recorded in the week ending 5 March 2022 – 65 cases more than in the previous week. Urgent collective community effort is needed to drastically reduce mosquito breeding habitats and slow down the rise in the number of dengue cases. The National Environment Agency (NEA) will soon deploy new alert banners at areas with persistently high [1] Aedes aegypti mosquito population in the coming weeks. These areas form a subset of locations with higher Aedes aegypti mosquito population, which NEA currently updates monthly on its website. The intent is to alert residents, community partners, and key stakeholders at such areas to take preventive measures against mosquito breeding, in order to reduce the risk of dengue.
2 The new purple-coloured banner will be added to NEA’s existing Dengue Community Alert System, which now includes the display of colour-coded banners (yellow, red, or green) to inform residents and members of the public about the dengue situation at their estates (refer to Annex A for Colour-coded banners under Dengue Community Alert System).
3 This initiative complements existing vector control operations and community outreach efforts (refer to Annex B for Surveillance of Aedes aegypti mosquito population with NEA Gravitraps).
4 We urge residents and premises operators to check the NEA website regularly, and to use the myENV app to receive notifications on areas with higher Aedes aegypti mosquito population. Residents living at these areas, regardless of whether or not the purple alert banners are deployed, are advised to be vigilant and take preventive measures against mosquito breeding, including doing the Mozzie Wipeout at least once a week to remove stagnant water.
Mozzie Wipeout ‘B-L-O-C-K’
Break up hardened soil
Lift and empty flowerpot plates
Overturn pails and wipe their rims
Change water in vases
Keep roof gutters clear and place BTI insecticide
5 Areas with higher Aedes aegypti mosquito population are at greater risk of dengue, as more mosquitoes can accelerate dengue transmission once cases are present in the neighbourhood. Such areas can be on average three to ten times more likely to develop into large dengue clusters, compared to areas with lower mosquito populations.
6 As of the week ending 5 March 2022, there have been more than 1,500 reported dengue cases this year. The weekly number of reported dengue cases this year has climbed steadily in the past eight weeks, with a sharp jump to 264 cases in the latest week. A contributing factor and key concern is the high Aedes aegypti mosquito population detected in the community, which has increased by about nine per cent in January 2022 compared to in the same period last year (January 2021). If left unchecked, the current high Aedes aegypti mosquito population – together with circulation of the previously uncommon dengue virus serotype 3 (DENV-3) and sizeable proportion of people still staying in and working from home – may lead to a surge in dengue cases in the coming months. NEA therefore urges members of the public and other stakeholders to stay vigilant and not let their guard down, as dengue remains a serious public health threat.
7 Mr Chew Ming Fai, NEA Deputy Chief Executive Officer and Director-General Public Health, said, “Our dengue prevention efforts are not only focused on dengue cluster areas, but include non-dengue cluster areas that have higher Aedes aegypti mosquito populations. The new purple alert banners will serve as useful visual reminders for stakeholders, partners, and residents to take pre-emptive measures to reduce potential mosquito breeding habitats, lower the risk of dengue transmission, and prevent clusters from being formed. Taking a pre-emptive approach in heightening dengue awareness and mobilisation of the community for dengue prevention efforts, is key to our vector control strategy.”
[1] NEA monitors the data collected from our island-wide Gravitrap surveillance system. Areas with ‘persistently high’ Aedes aegypti mosquito population are areas that have higher mosquito populations compared to others, for three months or more.
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For more information, please submit your enquiries electronically via the Online Feedback Form or myENV mobile application. Alternatively, you contact us at 6225 5632.
ANNEX A
Colour-coded banners under Dengue Community Alert System
Purple: Areas with persistently high Aedes aegypti mosquito population
Residents living in areas with persistently high Aedes aegypti mosquito population should practise the Mozzie Wipeout ‘B-L-O-C-K’ steps at least once a week to remove stagnant water.
Mozzie Wipeout ‘B-L-O-C-K’
Break up hardened soil
Lift and empty flowerpot plates
Overturn pails and wipe their rims
Change water in vases
Keep roof gutters clear and place BTI insecticide
Red: High-risk area with 10 or more dengue cases
Residents living at dengue cluster areas with red banners should regularly practise the Mozzie Wipeout, and carry out the three protective actions against dengue: ‘Spray, Apply, Wear’ or ‘SAW’ in short:
1. Spray insecticide in dark corners around the house
2. Apply insect repellent regularly
3. Wear long-sleeve tops and long pants
Yellow: High-risk area with 2 to 9 dengue cases
Residents living at dengue cluster areas with yellow banners should regularly practise the Mozzie Wipeout, and carry out the three protective actions against dengue: ‘Spray, Apply, Wear’ or ‘SAW’ in short:
1. Spray insecticide in dark corners around the house
2. Apply insect repellent regularly
3. Wear long-sleeve tops and long pants
Green: No new dengue cases; Dengue cluster closed and under surveillance
Residents living in areas where dengue clusters have closed are advised to remain vigilant and take necessary mosquito prevention measures, including doing the Mozzie Wipeout at least once a week to remove stagnant water.
Mozzie Wipeout ‘B-L-O-C-K’
Break up hardened soil
Lift and empty flowerpot plates
Overturn pails and wipe their rims
Change water in vases
Keep roof gutters clear and place BTI insecticide
ANNEX B
Surveillance of Aedes aegypti mosquito population with NEA Gravitraps
- The Gravitrap, developed by NEA’s Environmental Health Institute (EHI), is designed to attract and trap female adult Aedes mosquitoes that are looking for sites to lay their eggs. Female mosquitoes attempting to lay their eggs in the traps will be captured and prevented from biting people. The Gravitrap also captures and prevents the emergence of any mosquitoes from eggs that are laid in the trap.
- Gravitraps, when distributed across an area, help to monitor the Aedes mosquito population in the area and its vicinity. In January 2020, NEA completed the deployment of Gravitraps to private landed residential estates, complementing those deployed at HDB estates since 2017. We now have more than 68,000 Gravitraps deployed at public and landed residential estates, to monitor the Aedes mosquito population in Singapore.
- The data on mosquitoes caught in these traps have guided NEA’s inspection focus, enabling more targeted deployment of limited manpower resources. The traps have also played a role in helping NEA to remove adult Aedes aegypti mosquitoes, including female mosquitoes infected with dengue. Deployment of Gravitraps complements the efforts of the community, owners of premises and other stakeholders, in suppressing the mosquito population.
- To strengthen our dengue control strategy, information on areas with higher Aedes aegypti mosquito population is updated monthly on the NEA website (and myENV mobile app). The sharing of mosquito population data serves as useful indicators for early intervention for our partners and stakeholders to take necessary preventive measures, to reduce the mosquito population and thus risk of dengue transmission.
- Gravitraps are usually deployed along common corridors of residential premises/estates. NEA officers will check and maintain the Gravitraps regularly, to ensure that they are functioning properly. If the Gravitraps are misplaced or toppled, this disrupts our surveillance network and could cause our NEA officers to search for mosquito breeding sites in the wrong areas, resulting in delays in tackling the mosquito situation. We therefore seek the cooperation of the public not to remove or tamper with the Gravitraps. If members of the public come across Gravitraps that have been toppled, please submit your feedback electronically via the Online Feedback Form or myENV mobile application. Alternatively, you can contact us at 6225 5632, so that our NEA officers can follow up.
Figure: NEA Gravitrap