Update on Project Wolbachia and Reason for Spike of Dengue Cases in First Quarter 2019

Mr Melvin Yong Yik Chye asked 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.

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.

As a regional transport hub, Singapore is vulnerable to the transmission of infectious diseases. NEA and 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.

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.

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.

Second, NEA brought forward the launch of the 2019 National Dengue Prevention Campaign to 7 April this year. 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.

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 Phases 1 and 2 field studies for Project Wolbachia in 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.

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.

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.

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.

I would like to take this opportunity to thank all our stakeholders, local Advisers, grassroots leaders and volunteers, for your efforts in our dengue prevention initiatives. 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 five-step Mozzie Wipeout. The Government alone cannot prevent dengue transmission in Singapore. We must remain vigilant and work together to keep dengue at bay.

Mr Speaker, I thank the Senior Minister of State for her update on Project Wolbachia in Singapore. I have three supplementary questions. The first is, why has the study taken so long as the start of Phase 1 was in October 2016 and it has been almost three years now. Compared to many other countries, we seem to be slower in our pace of introduction of Wolbachia as a dengue and Zika suppression method.

Secondly, the Senior Minister of State talked about scalability as well as sustainability of releasing male mosquitoes. My second question is, will the NEA consider adopting the World Mosquito Programme's Wolbachia method, which is to release both male and female Wolbachia mosquitoes so that it is self-sustaining. This has found success in several hotspots internationally, including Australia.

My third question has to do with availability of information on Project Wolbachia as well as educating the public. It seems that the public is aware of various methods but may not be so clear about the benefits of Wolbachia. In Australia, for example, they involved school students as part of the release of male Wolbachia mosquitoes so that they bring the message home to their families as well. So, whether NEA will consider expanding on the education and information available on this project.

I thank the Member for his three supplementary questions. Firstly, regarding why it has taken some time to implement Phase 1 to Phase 3 of Project Wolbachia technology. Let me say that we are actually adopting a systematic phased approach for the field trials because we need to study the various aspects of using this technology. In fact, as I have said in my answer earlier, when we did Phase 1, it gave us valuable information on the deployment of the technology particularly because, we are the first in the world to implement this technology in a tropical, highly urbanised and high density landscape. From the information that we got about the behaviour of the male Wolbachia-Aedes aegypti, we were able to then implement Phase 2 in terms of where to launch and deploy these mosquitoes to both higher floors and lower floors, as well as having larger areas and buffer sites to improve the suppression of the Aedes aegypti mosquito population.

For the Phase 3 field study, as I have said, what we aim to do is to determine how the suppression can be sustained through the seasonal fluctuations of the Aedes aegypti mosquito population and also over a larger study area and in order to determine the number of male Wolbachia-Aedes mosquitoes that is required to sustain the suppression that has been achieved in Phase 2. That is why for Phase 3, we have actually expanded the study site, the same study sites but to a larger area, 1.6 to 2.2 times. And as I have said, we want to carefully and rigorously evaluate the results to see if the suppression can be sustained, before we consider deploying this on a larger scale.

In fact, let me say that, to our knowledge, for countries that have adopted the Wolbachia technology, even though the technology has developed quite quickly, none of them has actually gone beyond field trials into full scale implementation. Australia, I understand has completed the field trials but they have not expanded the project. Even in Guangzhou, what they have done is similar to Singapore, they have actually just expanded the field trials.

Another point that I would like to highlight is that, the Wolbachia technology is meant to complement and enhance our existing vector control strategies and not to replace them. So, source reduction and so on, are still important and is in fact critical to the success of this Project Wolbachia technology and we will have to continue to persist with such efforts in order to restrict and reduce the number of dengue cases.

Regarding education, let me say that we are working on educating both the residents within the field trial study sites as well as the general public through various means such as the mass media, for instance, by having articles on the Wolbachia technology, community outreach events as well as seminars. Since 2012, we have organised more than a hundred seminars and outreach events to reach out to the academia, the medical and healthcare professionals, teachers, students, NGOs, grassroots leaders, members of the public and residents. We also have the Project Wolbachia Learning Journey which we offer to members of the public, students, residents from the study area, to visit our mosquito production facility, so that they will have a better understanding of the processes involved and the production of our Wolbachia-Aedes aegypti mosquitoes. We will continue to do that.

With regards to scaling and sustainability, I think I have more or less touched on the question.

I thank the Senior Minister of State. Many of the private condominiums in my constituency – and I have many – are stepping up anti-mosquito fogging. It has come to a point where there is some kind of fogging almost every day. The residents tell me, "If I do not fog, then the mosquitoes next door will come over to my side". So, I have two questions. One, can the Ministry explain if this fogging is useful and is effective because I have some understanding that the mosquitoes will eventually become resistant to some of the chemicals being used. That is one. Two, because there is so much fogging taking place and it is becoming like a competition, can NEA consider coordinating such fogging activities in private estate clusters where there are quite a number of condominiums and they are all fogging at some point in the week. And if it is effective, then I think we should do something about it. In fact, if somebody coordinates, then if we can aggregate demand, it may also bring the costs down for the area or for the estate.

I said earlier in my reply that we have a Gravitrap surveillance system. It is deployed island wide and the idea is to identify where there is a high concentration of Aedes aegypti mosquito population. So, fogging is normally used when there is a dengue cluster, because fogging and misting is to kill the adult mosquitoes and also where there could be a high concentration of mosquito population.

The most effective and primary method really is source-reduction, that is, preventing mosquito breeding rather than fogging and misting. But there is a use for fogging and misting; as I have said, during a dengue cluster or when there is a high mosquito population. When there is a dengue cluster, you also have indoor space spraying to kill the adult mosquitoes which may be infected.

With regard to fogging becoming a competition amongst condominiums, I think the fogging schedule is determined by the MCs of the condominium. So, they need to decide if there is a real need to do fogging so frequently.

First, I want to thank NEA for allowing Jurong students and parents to visit the Wolbachia production facility in Jurong. It was very well-received and we were very encouraged by the project. I have two questions to ask the Senior Minister of State.

First, since the production facility is in Jurong, is there any plan to extend the Wolbachia project in Jurong as well because there are also dengue clusters? Two, is there a plan to expand the Wolbachia production facility?

As I have said, the Wolbachia technology is still under development and, at the moment, we are undertaking trials and field studies. So, we will have to evaluate the results of Phase 3 of the field study carefully and rigorously before we decide if we should deploy the technology on a larger scale. But at the same time, in terms of production of the Wolbachia-Aedes mosquitoes, we are actually looking, as I have alluded to also in my reply, at production and release through automation, improving the productivity and production efficiency as well as the quality of the Wolbachia-Aedes mosquitoes produced at the production facility. For instance, we work with various companies like Orinno Technology and Verily Life Sciences to develop innovative devices, such as a larvae counter, pupae counter and sorter, adult mosquito sex sorter, mosquito launcher and so on to make it more effective and efficient in producing these Wolbachia-Aedes mosquitoes.