Information on areas with higher mosquito population made available since August 2019 to facilitate pre-emptive dengue control efforts, even as Aedes aegypti mosquito population increased by 32 per cent from September to October 2019

Singapore, 27 November 2019 – Since 13 October 2019, the number of dengue cases in Singapore has steadily increased over a five-week period (13 October to 16 November 2019), before coming down in the last week (17 to 23 November 2019). There are multiple reasons for the high number of dengue cases in recent weeks, with the likely contributors being the high Aedes mosquito vector population, warmer temperature, and low immunity in the human population. The most salient factor is likely the 32 per cent increase in the Aedes aegypti adult mosquito population in October, compared to in September 2019. To facilitate pre-emptive ground action, since August 2019, NEA has shared with Town Councils and other stakeholders information on areas with higher mosquito population [www.nea.gov.sg/dengue-zika/Aedes]. This is so that stepped-up preventive measures can be taken early to prevent dengue clusters from forming. We have also observed a 55 per cent increase in the detection rate of Aedes aegypti larval habitats found in homes in October, compared to in September 2019. As the travel season approaches, we urge all families who are planning to go on vacation to mosquito-proof their homes before they travel. 

2.         NEA has reached out to stakeholders with the Gravitrap surveillance data, to help them prioritise their dengue prevention and control measures, and to target areas with higher mosquito population. We urge everyone to take immediate action to eliminate potential mosquito breeding habitats, and join in the collective effort to stop dengue transmission.

3.         The increase in dengue cases at year-end has been observed in certain, but not all, years in the recent past. For example, in 2013 and 2015, there were year-end spikes in the number of dengue cases, and on both occasions, we entered the following year with an atypically high number of dengue cases. There is a possibility of the number of dengue cases continuing to rise further as we approach this year-end. 

Dengue Situation in 2019

4.         The total number of dengue cases reported in 2019 (as of 23 November 2019) is 14,658. This is about five-and-a-half times more than that in the same period of 2018, but about two-thirds the number of cases seen in the dengue outbreak of 2013 (Figure 1). As of 26 November 2019, there are 76 active dengue clusters reported. The five largest clusters are located at Choa Chu Kang Avenue 2, Elias Road, Jalan Bangau, Jurong West Street 61, and Begonia Lane. The majority of mosquito breeding habitats found at most of these clusters are within residential premises (refer to Annex A for inspection findings at the top five dengue cluster areas).

5.         NEA and our partners in the Inter-Agency Dengue Task Force (IADTF) have kept up inspections at dengue cluster areas. In addition, NEA has shared with Town Councils and stakeholders information on areas with higher mosquito population, so that stepped-up preventive measures can be taken. All residents living in dengue cluster areas are strongly encouraged to cooperate with NEA officers, and to facilitate their checks and indoor misting in their homes. As the Aedes aegypti mosquito has adapted well to the urban environment, it is critical to eradicate mosquito breeding habitats and adult mosquitoes. Adult Aedes aegypti mosquitoes tend to rest inside homes. Accessing all homes in a dengue cluster area as quickly as possible, with the help of the local Grassroots and residents, helps keep the community safe. Residents living in dengue cluster areas are also strongly encouraged to protect themselves, by applying mosquito repellent regularly and keeping their homes free of stagnant water.

6.         NEA has maintained a high tempo of preventive inspections for mosquito breeding as well as dengue cluster operations, in order to curb dengue transmission. Between January and September 2019, about 703,000 inspections were conducted islandwide, and NEA uncovered about 11,700 mosquito breeding habitats. To safeguard public health, NEA will not hesitate to take enforcement action against anyone found to have created conditions favourable for the propagation or harbouring of vectors. As of September 2019, about 6,300 [1] enforcement actions have been taken against premise owners for mosquito breeding. NEA will continue with these inspection and enforcement efforts in 2019. 

Figure 1. Number of Dengue Cases from 2013 to 2019 (as at Epidemiological Week (E-week) 47)

Mosquito-Proof Homes Before Travelling

7.         Those planning to go on vacation should mosquito-proof their homes before they travel. As the majority of mosquito breeding is found in homes, we can all help to keep our neighbourhoods free from dengue by taking these mosquito prevention measures:

• Covering all toilet bowls in your home, and sealing off overflow pipes of the flushing cisterns

• Covering all floor traps

• Adding sand granular insecticide (temephos or Abate) to places where mosquitoes could potentially breed, and places where stagnant water cannot be removed

• Clearing debris and blockages, and placing Bti insecticide in roof gutters

• Turning over all water storage containers and wiping dry the rims

• Asking a relative or close friend to check your home regularly for stagnant water, if you are going away for a long period of time

• Leaving your contact details with your neighbours or the neighbourhood police post/ centre, so that you can be easily reached

8.         We encourage everyone to be an advocate of dengue prevention, and to remind his or her family members and neighbours to join in the collective effort to stop dengue transmission, by regularly doing the 5-step Mozzie Wipeout. All of us, including residents, contractors and business owners, have a part to play in preventing dengue. The latest updates on the dengue situation can be found on the NEA website, stop Dengue Now Facebook page, and myENV app.