As of 4 August 2020, there have been 22,403 reported dengue cases this year. While there was a more than a 20 per cent decline in cases (of 412 cases) last week, the weekly numbers remain high, and more than 600,000 households are located in over 390 dengue clusters islandwide. As we are still in the midst of the traditional dengue season, urgent collective community effort is critical to bring down the case numbers further. While the National Environment Agency (NEA) is working with all Town Councils to step up dengue prevention efforts in an intensive two-week islandwide exercise, all residents, especially those living in dengue cluster areas, should do the three protective actions as listed below, to protect themselves and their loved one against dengue.

Protective actions against dengue: ‘SAW’

  1. Spray insecticide in dark corners around the house
  2. Apply insect repellent regularly
  3. Wear long sleeves & long pants

Such protective measures are important to break the cycle of transmission, by preventing the Aedes mosquito from biting human hosts and spreading the dengue virus to others in the vicinity. Given the surge in dengue cases, high mosquito population, and more people working from home, there is a need to deny more hosts for the day-biting Aedes mosquitoes to bite. As the traditional dengue peak season lasts a few months, from May to October, NEA urgently seeks the cooperation of all residents and stakeholders to do their part to complement NEA’s efforts, by doing protective actions such as SAW, regularly doing the Mozzie Wipeout, and cooperating with our NEA officers during our inspection rounds.

Dengue cluster situation update

The number of weekly dengue cases has declined from a high of 1,792 in the third week of July, to 1,380 in the week ending 1 August 2020. In tandem, there has been a decline in number of dengue clusters, from 434 last Tuesday (28 July 2020) to 391 as of yesterday (4 August 2020). However, continued vigilance is needed, as the number of weekly dengue cases remains persistently high at above 1,000. With the concerted efforts of NEA and the community/ stakeholders, the 134-case cluster at Chu Lin Road/ Elizabeth Drive, 115-case cluster at Bidadari Park Drive / Woodleigh Link, 84-case cluster at Da Silva Lane / Florence Close, 74-case cluster at Alkaff Crescent, and 48-case cluster at Ah Hood Road, have been closed. Overall, we have closed about 79 per cent, or 1,466 of 1,857, dengue clusters notified, since the start of this year. However, there are still large dengue clusters located at Aljunied Road / Geylang Road / Geylang East Avenue 1 and 2, Bukit Panjang Ring Road, Arthur Road, Aljunied Road / Geylang Road / Guillemard Road, and Arnasalam Chetty Road / Kim Yam Road, where intensive vector control operations are ongoing.

Some dengue clusters also have a faster rate of disease transmission, such as the 312-case cluster at Aljunied Road / Geylang Road / Geylang East Avenue 1 and 2, 286-case cluster at Arthur Road, 229-case cluster at Aljunied Road / Geylang Road / Guillemard Road,  229-case cluster at Arnasalam Chetty Road / Kim Yam Road, 215-case cluster at Brighton Crescent / Lichfield Road, 211-case cluster at Geylang East Avenue 1, 169-case cluster at Bartley Road, 146-case cluster at Dakota Crescent, 145-case cluster at Bedok North Avenue 1, 135-case cluster at Balam Road, 131-case cluster at East Coast Road, 128-case cluster at Cassia Crescent, 118-case cluster at Desker Road, and 103-case cluster at Kensington Park Drive, where there is an average of about two to four cases reported per day in the past two weeks.

NEA continues with stepped-up vector control and community outreach efforts

In addition to ongoing islandwide inspections, NEA has continued with its intensified dengue inspection and outreach efforts, and conducted more than 552,000 inspections islandwide between January to July this year. NEA is also working with partners such as the People’s Association, Ministry of Education, Early Childhood Development Agency, Ministry of Health / Agency for Integrated Care, Ministry of Manpower and National Parks Board, to distribute educational materials and mosquito repellent to residents in dengue cluster areas. Volunteers have also been deployed every weekend since end-June to engage residents at large dengue cluster areas, reaching out to almost 55,000 people. These efforts will continue at other large dengue cluster areas over the upcoming weekends. Engagement efforts have also been supported by mass publicity on TV, print, out-of-home and online platforms, as well as through SMS blasts, to urge residents to protect themselves from the risk of being bitten by mosquitoes and to Do the Mozzie Wipeout regularly.

Every individual has a part to play in breaking dengue transmission

All residents living in dengue cluster areas are strongly encouraged to cooperate with NEA officers, and facilitate their checks and indoor misting in their homes. This would help to quickly eradicate mosquito breeding habitats and adult mosquitoes in homes, to break disease transmission. Between January to July this year, NEA detected about 13,800 mosquito breeding habitats islandwide. This is about 40 per cent higher than in the same period in 2019. As the Aedes mosquito’s life cycle can be as short as seven days, it is important to Do the Mozzie Wipeout at least once a week.

In addition, it is important for residents living in dengue cluster areas to take proactive steps to protect themselves and their loved ones against dengue. Chief Executive Officer of NEA, Mr. Tan Meng Dui, said “NEA has been going all out and working with stakeholders in our fight against dengue. The current conditions are challenging, with a combination of high viral load with the record number of weekly cases, high mosquito population with the dengue season in full swing, and also more targets with more people working from home. We urge residents living in dengue cluster areas to protect themselves against mosquito bites, by doing the three simple steps – spray insecticide at dark corners, apply insect repellent, and wear long-sleeve tops and long pants. In our fight against dengue, both defensive and offensive actions are important. Such concerted individual and collective efforts are the most effective way to break the dengue transmission chain, and bring the dengue situation under control.”

NEA encourages everyone to use the resources available on our website and myENV app to receive updates on the dengue situation, and to take proactive action to protect themselves and their loved ones. NEA has also developed a ‘Check and Protect’ checklist, highlighting common mosquito breeding habitats, which is available for download at go.gov.sg/dengue-checklist.

Regular updates on the dengue situation can be found on the NEA website, Stop Dengue Now Facebook page, and myENV app. The public can also download the myENV app to get regular alerts on dengue clusters and areas with higher Aedes aegypti mosquito population.

Protective Actions to Take Against Dengue

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Factors leading to the dengue surge

  • A confluence of factors is contributing to the surge in dengue cases this year. While the proportion of positive dengue samples identified as DENV-3 reduced from 42.6% in April to 35.6% in June, and those identified as DENV-2 increased from 39.4% in April to 52.3% in June, the proportion of DENV-3 cases was dominant for the four months of this year, from January to April 2020.
  • This serotype was last seen in a dominant position in Singapore about three decades ago, which means there is low immunity in our population and rapid disease transmission. The majority of the infections this year are of DENV-2 and DENV-3. A large proportion of our population continues to be susceptible to dengue, given our population’s low immunity and successful vector control efforts over the years.
  • Population immunity against DENV-2 and DENV-3 is low, at 14% and 2.7% respectively, in the 16 to 20 year old age group (source: NEA study). This likely explains the unusually high number of weekly cases, hovering between 300 to 400, since the start of the year.
  • The high base of dengue cases in the first few months of the year means a high “viral load” within the population; this is a situation that is conducive for an outbreak once the other favourable conditions are aligned, viz, increase in the vector (Aedes mosquito population) and human targets.
  • Second, building on the high dengue case trend of the first four months, the sharp spike in dengue cases, by 32% from April to May, should be seen against a confluence of “new” factors beginning from about May 2020.  The warmer and wetter weather, typical of the traditional peak dengue months from May to October, as well as the observed increase in the mosquito population in many areas, would have carried the momentum of the high dengue case load of the first four months of the year over to the following months.
  • NEA’s Gravitrap surveillance system has detected a 30 per cent increase in the Aedes aegypti mosquito population from May to June 2020, compared to from February to March 2020. As we are in the warmer months of the year, we expect the high Aedes aegypti mosquito population to be sustained, unless additional efforts are taken to remove stagnant water in the environment and prevent mosquito breeding.
  • Third, the sharp spike in dengue cases coincided with the two-month Circuit Breaker (CB) period. The weekly number of dengue cases started to rise above the 300 to 400 band from the beginning of May 2020, or slightly more than three weeks after the start of CB. With more people staying at home, there would be more human hosts for the female Aedes aegypti mosquitoes to target, which is a day-biter and harbours within the indoor environment, and this would have partly contributed to the recent increase in cases.
  • Other factors at play during the CB period could have also compounded the dengue situation. These include the reduction in some landscaping works due to manpower shortages, cessation of the bulk of construction activities which would have hampered good housekeeping of construction sites, and possibly better health-seeking behaviour by the public who feel unwell or notice symptoms arising from the current COVID-19 situation.

NEA’s enhanced dengue control efforts

  • NEA takes a multi-pronged approach to dengue control, comprising vector control measures, stakeholder engagement, as well as community mobilisation and public communications. In anticipation of the surge this year, several enhanced efforts have been undertaken this year and are ongoing.
  • NEA completed roll-out of the Gravitrap surveillance system to landed estates in early 2020. This enhanced surveillance complements the Gravitrap surveillance data collected from HDB estates, and has enabled NEA to conduct more targeted and effective inspections and vector control operations.
  • Since end 2019, NEA has also made available information on areas with relatively higher Aedes aegypti mosquito population on the myENV app and website. This is to increase the awareness of residents living in these areas, so that they can take preemptive steps at source reduction and to bring down the mosquito population. Mosquito population is a lead indicator of a dengue cluster, and by putting out this information, NEA aims to equip residents with information that they can act on, to take proactive steps to prevent dengue.
  • The National Dengue Prevention Campaign launch was brought forward to March this year, to alert residents on the need to fight dengue ahead of the start of the dengue peak season.
  • With the COVID-related measures limiting face-to-face engagement efforts, additional efforts were taken to reach out to residents directly through ramping up engagement via digital and mobile platforms.
  • As visual cues within neighbourhoods have been found to be effective in creating awareness, NEA has expanded the number of dengue alert banners displayed at neighbourhood precincts of dengue cluster areas, and brought this awareness closer to homes by putting up dengue posters at the individual HDB block level. SMS blasts have also been sent to targeted dengue cluster areas, to remind residents to check their homes for stagnant water and Do the Mozzie Wipeout.
  • NEA has also been stepping up outreach efforts at dengue cluster areas – including house visits and the distribution of mosquito repellent and outreach materials to residents. Volunteers and poster walkers will also be deployed at town centres at dengue cluster areas, to augment outreach efforts.
  • In May 2020, NEA worked with the Ministry of Health, Polyclinics and General Practitioners, to provide over 300,000 bottles of mosquito repellent for distribution to patients who are suspected to have dengue. This is to help break the dengue transmission chain, especially in cluster areas or where the mosquito population is high. The messages on spraying aerosol insecticide in dark corners of the home have also been enhanced, to educate residents on how to protect themselves and their loved ones.
  • NEA has been working with all Town Councils to step up inspections and vector control operations in common areas, to ensure drains are well maintained, common areas are kept litter-free, and stagnant water is removed or treated. This is part of a 2-week intensive effort at vector control to help break the dengue transmission chain. Town Councils are also urged to work with NEA to coordinate chemical treatment, such as fogging, misting and larviciding, in dengue clusters, to bring down the adult mosquito population.
  • NEA continues to work closely with Grassroots Advisers and Leaders and community volunteers, to reach out to more residents to advise them to get rid of mosquito breeding habitats at home and the importance of applying repellent and spraying insecticide regularly.
  • Since 15 July 2020, NEA has also imposed heavier penalties for households found with repeated mosquito breeding offences, multiple mosquito breeding habitats detected during a single inspection, and mosquito breeding detected after having received a legal notice from NEA. Enforcement has also been tightened for construction sites and Town Councils.

Inspection Findings at the Top Five Largest Dengue Clusters
Information as of 22 July 2020

S/N

Cluster locality

  • No. of cases
  • Date of notification
  • Proportion of mosquito breeding in homes
Premises detected with repeated mosquito breeding and/ or multiple mosquito breeding [1]

1

Aljunied Rd / Geylang Rd / Geylang East Ave 1,2 / Geylang East Ave 1 (Blk 132, 133, 134) / Geylang East Ctrl (Blk 120, 122) / Guillemard Rd / Jln Molek / Jln Suka / Lor 22, 24, 24A, 25, 25A, 26, 27, 27A, 28, 29, 30, 32 Geylang / Sims Ave
  • 312
  • 21 Feb 2020
  • 55%

2 premises detected with repeated breeding

2 premises detected with multiple breeding

2

Bt Panjang Ring Rd(Blk 537, 539, 541, 545, 609, 611, 613, 615, 617, 619, 620)/Jelapang Rd (Blk 528, 530, 536, 538, 540, 542, 543, 544) / Senja Lk (Blk 652) / Senja Rd / Senja Rd (Blk 601-608, 610, 612, 614, 616, 618, 621, 622, 623, 624) / Woodlands Rd
  • 292
  • 27 May 2020
  • 79%

 

3

Arthur Rd/Arthur Rd (Arthur 118)/Bournemouth Rd/Broadrick Rd/Clacton Rd/Cres Rd/Fort Rd/Jln Nuri/Jln Seaview/Jln Sedap/Margate Rd/Mayfield Ave/Meyer Pl,Rd/Mountbatten Rd/Peach Gdn/Ramsgate Rd/Ringwood Rd/Walton Rd
  • 286
  • 5 May 2020
  • 71%

 

1 premises detected with multiple breeding

1 premises detected with repeated breeding

4

Aljunied Rd / Geylang Rd / Guillemard Rd / Lor 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 Geylang / Lor Bachok / Lor Tahar ([email protected]) / Sims Ave, Way / Westerhout Rd
  • 229
  • 19 May 2020
  • 44%

 

5

ArnasalamChettyRd / DevonshireRd / DublinRd / JlnKuala / JlnRumbia / KillineyRd / KimYamRd / LloydRd / MartinPl / MohdSultanRd / OxleyGdn, Rd, Rise, Walk / RiverValleyCl, Rd / RobertsonQuay / RodykSt / St.ThomasWalk / TongWattRd / UnitySt
  • 229
  • 1 Jun 2020
  • 58%
5 premises detected with multiple breeding

 

 


[1] Repeated breeding refers to breeding detected during a re-inspection. Multiple breeding refers to more than 1 breeding habitat detected during a single inspection.

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