DENGUE EPIDEMIC

DENGUE EPIDEMIC:

1\. Dr Lily Neo asked the Minister for the Environment and Water Resources what new measures will be adopted by the National Environment Agency in

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fighting the present dengue epidemic after receiving the advice from the panel of dengue experts following their two-week study in Singapore.

The Minister for the Environment and Water Resources (Assoc. Prof. Dr Yaacob Ibrahim): Mr Speaker, Sir, during their 2-week study, the expert panel looked into the epidemiological features of the current dengue outbreak, conducted field trips to observe dengue control operations and reviewed the national framework for dengue control. The panel recognised that Singapore has one of the best dengue control programmes in the world and had also supported our outreach efforts to involve the community and the private sector. However it recommended that more research should be carried out to better understand dengue transmission dynamics and changes in mosquito's behavior, and to enhance the vector surveillance systems.

Research on Aedes Mosquitoes and the Dengue Virus

We agree with the expert panel that more research be done to enhance our dengue surveillance and control efforts. Effective prevention and control of dengue requires an active laboratory-based dengue surveillance programme to provide early warning for possible dengue outbreaks.

In this respect, studies to understand prevailing serotypes and dengue virus strains are already being carried out in various laboratories such as the Environmental Health Institute (EHI), Genome Institute of Singapore (GIS) and some of our hospitals such as Tan Tock Seng Hospital. To ensure that there is quality control for these lab tests, MOH has designated the Public Health Laboratory currently sited at Singapore General Hospital (SGH) as the national reference laboratory for all infectious diseases. It will be supported by the Environmental

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Health Institute (EHI) of NEA in the area of vector-borne diseases including dengue.

As pointed out by the expert panel, we also recognise that transmissions can occur at sites away from home or go unreported. There are asymptomatic dengue cases, where a person infected with dengue exhibits no symptoms. We will intensify our research efforts and have identified a number of research projects that will be undertaken by NEA and MOH.

Enhanced Mosquito Surveillance System

We will also improve on our operational vector surveillance system. NEA has been using ovitraps as a surveillance tool to detect mosquito activity to direct its vector control work. We will now study how to enhance this to provide early warning system to residents on increases in mosquito populations in their estates. This will allow actions to be taken before any dengue outbreak occurs. A pilot study will be conducted by NEA at Marsiling using ovitraps for monitoring the Aedes population.

Continuing Medical Education

The experts also affirmed the important role played by GPs in tackling dengue. MOH will intensify its efforts to educate GPs by continuing to circulate advisories to medical practitioners and convene seminars from time to time. This is to keep the medical professionals abreast of the latest developments in the epidemiology and clinical diagnosis to prevent and control dengue. In fact, MOH has worked with the College of Family Physicians to issue a handbook with the detailed guidelines on clinical diagnosis and management of dengue patients to all physicians.

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Private Sector Partnerships

The expert panel has endorsed NEA's programme to work with all the Town Councils (TCs) to put in place dedicated mosquito control programmes by November this year. In fact, 7 of the Town Councils have already implemented the programme. NEA will also work closely with our pest control industry to enhance its professionalism and to adopt best practices in fogging and other operational areas.

Need to Remain Vigilant

It is encouraging to note that our 7-day average daily number of dengue cases has progressively declined from 106 on 23rd September to 56 on 16th October 2005. But it is still too early to determine if the downward trend will continue. Dengue is a resurgent problem globally; and being endemic to the region, Singapore can expect dengue to recur on a regular basis. Hence, all of us must remain vigilant and diligent in playing our part to prevent mosquito breeding.

Dr Lily Neo (Jalan Besar): Sir, may I ask the Minister whether NEA should change its tactics and adopt more measures in this fight against dengue epidemic immediately, such as by targeting the mosquito larvae in the prevention of adult mosquitoes. Since the experts have confirmed that fogging is not that effective in Singapore, should that not be switched to focusing on looking for and treating all potential breeding sites?

Does the Minister agree that surely killing the mosquito larvae with larvicide is more efficacious because it arrests the source of hundreds of mosquitoes at source? Moreover, larvicide can continue to be effective for more than one month.

Lastly, may I urge the Minister to act decisively soonest and issue directives on

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better effective modes in this fight in view of the fact that the pest control industry is $50 million a year —

Mr Speaker: Your questions, please. No speeches.

Dr Lily Neo: —: and increasing in order to control the dengue fever and also save costs and efforts on updated techniques.

Assoc. Prof. Dr Yaacob Ibrahim: Sir, I agree with the Member that we have to tackle the problem at the source and that is why NEA has always adopted a source-reduction approach. And that approach has been endorsed by the World Health Organisation. Ever since we have been tasked to tackle this problem and ever since NEA was created, our challenge has always been to close the breeding sites and remove all breeding sites as quickly as possible. Every time, there is a case, MOH will alert us and we will deploy our officers down to where the infection has taken place, check thoroughly, both inside and outside, within the surrounding premises, to ensure that there are no breeding sites.

One of the things we did in this current challenge is that we have started carpet-combing across all constituencies. By this weekend, we should finish the exercise to explore what other potential breeding sites that may be occurring without our knowledge within the common areas, ie, outside the homes. It has revealed nothing new. We know what are the potential breeding sites. But, more importantly, we have found potential breeding habitats, in other words, there are no larvae found but water has been collecting and therefore we have passed this information back to the town councils so that they can then adopt a maintenance and vigilance approach in order to tackle this problem much quickly.

Once the pest control operators are in place with all the town councils they will then be subject to certain audits by NEA.

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But before that, we will work with the town councils to raise their level of maintenance and vigilance so that they can conduct checks regularly to ensure that we remove all potential breeding habitats within the common areas of the town councils.

The expert panel did not say that fogging is not effective. What they said specifically was that fogging is not effective in breaking epidemic transmission. What we have done is that we have started a small technical committee, headed by the professional industry together with NEA, to study the effectiveness of fogging. But, meanwhile, fogging will be one of the tools that we will use in this current challenge. It will complement all other efforts for evidence has shown that fogging can kill adult mosquitoes. So we will continue to study this particular technique in terms of effectiveness but, at the same time, we will continue to use it while trying to improve the professionalism of the industry.

On her final point about working with the industry, that has always been the operating procedure for NEA. We work very closely with the pest control operators. We have over the years upgraded the skills of the pest control operators and certainly, in this current instance, I would like to thank the pest control operators because they have come forward to work very closely with NEA to ensure that they can be effective on the ground.

I am confident, with the current efforts in place, we will be able to at least put this problem under control. But, as I mentioned in my answer, we know that this is a resurgent problem globally and therefore we have to continue with the efforts we have adopted so far in order to control this particular challenge.

Dr Lily Neo: Sir, the Minister mentioned the study of fogging. May I ask

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the Minister, in view of the present dengue epidemic, is it wise to wait for another six months' study on fogging before taking action on it, especially when fogging was already known to have unknown values with mosquito killing rate of less than 4% at best, confirmed by experiments overseas and reconfirmed by the foreign experts invited to Singapore recently?

Assoc. Prof. Dr Yaacob Ibrahim: Sir, I cannot argue about the figure because I am not so sure whether that is the correct figure, nor did the expert panel say that we should stop fogging. I think what the expert panel is trying to tell us is that we should not rely on fogging entirely.

While the study is being conducted by the technical committee, together with NEA, fogging as a practice is safe and we will continue to do fogging but we have also put in a new standard operating procedure where before any town council or any operator would like to carry out fogging they have to alert us one day in advance so that we can then monitor whether they are doing it correctly.

Dr Lily Neo: Sir, since we cannot get rid of dengue altogether and since Singapore emphasises on being the biomedical hub, can more research be done on disease surveillance for early warning on dengue epidemic, the genetic sequencing on dengue virus and on the development of vaccines against dengue?

Assoc. Prof. Dr Yaacob Ibrahim: Sir, I would like to assure the Member and Members of the House that that is exactly what we are doing now. We are basically moving upstream, conducting some research projects together within EHI and MOH, to study the various transmission dynamics whether the virus has mutated or not so that we can understand better this particular vector. So I would like to

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assure her that the research projects that we are conducting now will bear, if we are successful, some fruits that will be useful to us in how we control this vector. But, at the same time, we have to learn from others in terms of their experiences. So, NEA, together with MOH, will remain open to the experiences of other countries so that we can understand best what are the techniques that we have to adopt in our current challenge.

Dr Tan Cheng Bock (Ayer Rajah): Sir, I thought I heard the Minister say that there are asymptomatic cases. I would like to ask the Minister whether these asymptomatic cases are actually suspected dengue cases and we have to report these cases to the Ministry of Health. The Minister should be aware that these cases are viremic, ie, they do carry the viruses. How is his Ministry or the Ministry of Health managing these suspected dengue cases which are carrying potential reservoirs of viruses and could possibly re-infect the community?

Assoc. Prof. Dr Yaacob Ibrahim: Sir, that is exactly one of the research areas that we are looking into. We understand the difficulty with the asymptomatic cases because without the symptoms it will be difficult for us to alert the GPs on what to look out for so that we know that they are dengue cases or otherwise. One of the studies that both MOH and EHI will conduct will involve about 5,000 people, 11 years and older, and this will be carried out to determine the range of symptoms of dengue infection and the extent of asymptomatic infection in the current dengue epidemic. This study will also help to identify the risk factors associated with the dengue transmission and it is expected to be completed within six months.

One of the benefits of this research is that the knowledge of the proportion of asymptomatic cases will help us to

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determine to what extent dengue cases go unreported. That is the first thing that we need to know and a high proportion of such cases will drive the shift towards more preventive measures and this will also help our GPs to determine the spectrum of clinical symptoms to more efficiently identify dengue patients.