Parliament Q&A

Oral reply by Dr Amy Khor, Senior Minister of State for the Environment and Water Resources, to Parliamentary Questions on Dengue and Wolbachia on 7 May 2019

TOPICS: Dengue

Question by Mr Alex Yam Ziming: To ask the Minister for the Environment and Water Resources (a) whether he can provide an update on Phases 1 and 2 of Project Wolbachia in the control of the Aedes aegypti mosquito vector; (b) how long will the Phase 3 field study last; and (c) whether Project Wolbachia can be accelerated in light of the increased incidents of dengue infections in the first quarter of 2019.

Question by Mr Melvin Yong Yik Chye: To ask the Minister for the Environment and Water Resources (a) what are the causes of the sudden spike of dengue cases in the first quarter of 2019; (b) what are the measures in place to detect dengue cases early; and (c) what is the Ministry's plan to reduce dengue cases especially during the dengue peak seasons.

Answer by SMS Amy Khor:

The National Environment Agency (NEA) has reported 2,200 cases of dengue in the first quarter of 2019. This was more than three times compared to the same period in 2018, but below the number of cases reported during the epidemic years of 2013 and 2014. Neighbouring countries have also reported increases in dengue cases in recent months. Contributing to this situation is a persistently high Aedes aegypti mosquito population in the community, as detected by the NEA Gravitrap surveillance system.

2 As a regional transport hub, Singapore is vulnerable to the transmission of infectious diseases. NEA and the Ministry of Health (MOH) have put in place a robust surveillance system to detect dengue and other vector-borne diseases. This system comprises vector surveillance, virus surveillance and dengue case surveillance. NEA has an island-wide network of 50,000 Gravitraps to monitor the mosquito population, and will add another 14,000 Gravitraps in the second half of 2019. Data from this network guides NEA’s vector control efforts, allowing officers to quickly zero in on the areas with high mosquito population.

3 NEA’s laboratory-based virus surveillance system monitors dengue virus serotypes and provides early alerts when there is a serotype switch. Historically, such switches have preceded large dengue outbreaks. Further, NEA, together with the National University of Singapore, has developed a model which helps us to forecast dengue incidence. This allows NEA to coordinate an effective pre-emptive response to impending dengue outbreaks.

4 NEA anticipates an increasing trend of dengue cases in the warmer months ahead, and has taken concerted efforts to stem dengue transmission. First, NEA, together with various agencies represented in the Inter-Agency Dengue Task Force, have stepped up checks and conducted more than 224,000 inspections in the months leading up to the peak dengue season. About 2,900 instances of mosquito breeding were removed.

5 Second, NEA brought forward the launch of the 2019 National Dengue Prevention Campaign to 7 April 2019. Together with Grassroots Advisers and leaders and Dengue Prevention Volunteers, NEA has been raising awareness that clean and stagnant water in homes are potential breeding habitats for mosquitoes, and galvanising the community to step up dengue prevention efforts. More than 8,500 volunteers have been trained to conduct patrols and house visits to share dengue prevention tips with residents.

6 Technology and innovation is another key pillar in dengue prevention efforts. NEA is conducting trial releases of male Wolbachia-carrying Aedes aegypti mosquitoes to further suppress the urban Aedes aegypti mosquito population in the community. NEA has successfully completed the Phase 1 and 2 field studies for Project Wolbachia - Singapore. The Phase 1 field study was conducted from October 2016 to December 2017, and a 50% suppression of the urban Aedes aegypti mosquito population was achieved. More importantly, this initial phase provided NEA with valuable data on the behaviour of the Wolbachia-Aedes mosquito. This has helped NEA to design more effective release strategies for Singapore’s high-density and high-rise city environment.

7 As a result, the Phase 2 field study, conducted from April 2018 to January 2019, saw a significantly higher level of dengue vector population suppression of 70 to 80%. In this phase, NEA expanded the size of the study sites, and released male Wolbachia-Aedes mosquitoes at higher floors, in addition to releases at the ground floor. The results showed that a larger release site yielded improved population suppression results.

8 The Phase 3 field study has started in February 2019. NEA has further expanded the study sites at Nee Soon East and Tampines West by 1.6 to 2.2 times. NEA aims to determine if suppression of the Aedes aegypti mosquito population can be sustained in larger areas, and if a smaller number of male Wolbachia-Aedes mosquitoes can be released at each residential block to maintain the suppression. NEA is also developing automation for male Wolbachia- Aedes mosquito production and release, to ensure scalability of the technology.

9 NEA will evaluate the Wolbachia-Aedes technology carefully and rigorously before deploying it on a large scale. NEA will continue to provide regular updates on the progress of Project Wolbachia.

10 I would like to take this opportunity to thank all our stakeholders, local Advisers, grassroots leaders and volunteers, for your efforts. We continue to see many cases of mosquito breeding in homes. All it takes is a small amount of water the size of a 20-cent coin for mosquitoes to breed. With a short breeding cycle of seven days, keeping the mosquito population in check requires the joint effort of every individual and stakeholder in the community to eradicate mosquito breeding habitats by practising good housekeeping and doing the 5-step Mozzie Wipeout. The government alone cannot prevent dengue transmission in Singapore. We must remain vigilant and work together to keep dengue at bay.

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