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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
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.
Last updated: 07 May 2019
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