Debated in Parliament on 25 Feb 2013.
Mr Yee Jenn Jong asked the Minister for the Environment and Water Resources (a) what steps have been taken to counter the threat from the recent spike in dengue cases, especially in the biggest hotspot area in East Coast Road/ Telok Kurau; and (b) of all sites found to be breeding mosquitoes in the past one year, how many were in (i) residential houses; (ii) construction sites; (iii)
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public outdoor spaces; and (iv) other areas.
Mdm Speaker, there has been, unfortunately, a significant increase in the number of dengue cases over the past two months, particularly in the eastern part of Singapore.
Please allow me to share some medical facts to set things in context. There are four types of dengue virus. If a person has been previously infected by one, he would usually develop life-long immunity to that particular serotype, but not to the other three. In fact, if that person is subsequently infected a second time, but by a different dengue serotype, the chances of complications become much higher. A change in the predominant dengue serotype that is circulating in our population can often lead to an epidemic because, by definition, if there is a change, the population lacks the immunity to this new circulating serotype. In the past, in fact, we had observed that the probability of a major epidemic breaking out increases every time you detect a serotype switch. This occurred in 2005, when Singapore had the worst incidence of a dengue epidemic.
At that point in time, in 2005, the predominant serotype changed from Dengue Type 2 to Dengue Type 1. Two years later, in 2007, we saw a smaller scale dengue outbreak when the predominant serotype switched from Dengue Type 1 back to Dengue Type 2. Thankfully, in the years since 2007, we have managed, through some very intensive efforts, to prevent a major dengue epidemic from breaking out. However, I must stress that this very success poses a potential problem because it means that the Singapore population has relatively low herd immunity against dengue and, therefore, each passing year that goes by without an epidemic paradoxically means our risk of developing an epidemic increases.
To complicate matters further, we have now seen more cases of Dengue Type 1 and Dengue Type 3 cases emerging over the last two months. This potential change in serotype has contributed to the latest spike in dengue cases.
The largest dengue cluster recorded so far is at the area around Telok Kurau and East Coast Road, and this is a Dengue Type 1 cluster. Seventy per cent of the breeding sites in this cluster were actually in residential homes. NEA has worked very closely with the local grassroots organisations and, in particular, with the local Member of Parliament, Mr Charles Chong, who has tirelessly knocked on doors to urge residents to empty their flower-pots, pails, containers and so on, in order to protect themselves and their neighbours from dengue.
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NEA has sent out advisories to all residents and put up dengue posters in the public areas. We have also sent SMS alerts to the residents and visitors in the area.
Breeding sites can also be found in other outdoor spaces, like construction sites. We have alerted LTA, HDB, PUB, NParks and Town Councils as well the local contractors, to step up their inspections of the areas under their respective charge, and NEA has helped to coordinate these efforts through an Inter-Agency Dengue Taskforce. We have been paying particular attention to construction sites, and there have been a few cases of irresponsible contractors failing to take adequate measures and we have subjected these contractors to composition fines, starting from $2,000 for first offence, and escalate thereafter. In fact, repeat offenders can face a maximum court fine of $50,000 and/or a jail sentence not exceeding six months. Last year, 900 mosquito-breeding offences were detected in construction sites, of which 626 were first-time offences.
Let me conclude by saying that this is a clear and present danger confronting Singapore. Remember that mosquitoes do not usually fly very far − on average, 150 metres, 200 metres. What this means is that if you have a dengue infection, you almost certainly caught it from another family member or neighbour living close by. The mosquito is simply a go-between. What this means then is that it requires individual and collective responsibility to eliminate mosquito breeding in your own home and in your own neighbourhood in order to protect yourself, your family members and your neighbours.
I would like to thank the Minister for the answer. I have two supplementary questions. But, first, I would like to declare that I live just next to the biggest hotspot area in East Coast Road. The first question is that, as an interested resident of the area, I would like to do my part to fight dengue. Other than making sure that there is no stagnant water at home, I would like to know what else can people do. I read that the Ministry had in the past given ovitraps to residents in some pilot schemes to trap the eggs that were being laid. I would like to know what has happened to that project and whether there is a plan to carry it on, and whether that has been effective.
My second supplementary question is this: I have read that the Ministry has stopped fogging because it is said that it is not effective. I would like to know why is it not effective, based on what sort of data, and would it be a plan to fog
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if there is a need to?
I thank the Member for those very relevant questions and also for reminding me that he is an interested party, as a resident in a hotspot. The first set of questions was: what else can you do? As I said, the most important strategy is still source eradication. So, you will be surprised at the creativity of the mosquitoes in finding new breeding spots. I will give Members an example. Even if you were to take a holiday for five days, and your home toilets are uncovered and unflushed, mosquitoes will happily breed in your toilet bowl. They will happily breed in gulley traps. They will happily breed in roof gutters if you have not secured them and you have not cleared them. And it only takes five to seven days. And it just shows you that you may think they have done a complete clearance, but there is always a possibility we have missed something, and there is always a possibility in that space of five days to a week, another life cycle has begun.
The second point is that this is, in a sense, a proximity disease. As I said earlier, mosquitoes do not fly very far. Therefore, you catch dengue from a neighbour or a family member. If you have a fever, it is worth remembering that you are a potential reservoir of infection. And this is relevant because, in fact, the majority of people who may carry the virus may not be diagnosed with dengue. And it is a clear reminder that if you have a fever and you are living in a hotspot, please see a medical professional who can make a specific diagnosis. And nowadays with the more sophisticated tests which are available, a diagnosis can be made within the space of hours or a maximum of a day.
The next point is, if you have been diagnosed or if there is a significant possibility that you are infected, your responsibility, first, is to get well yourself but, equally, remember you do not want to pass on that same virus to your family members, so prevent yourself from being bitten by mosquitoes using repellants or even good-old-fashioned mosquito nets. In the past, we used to do that but, nowadays, you hardly ever see a mosquito net. I think you probably have to go to the Beach Road surplus stores to find a mosquito net which we used from our army days. But, in fact, mosquito nets are very effective barriers to the transmission of the virus by mosquitoes. And I am not talking about preventing you from being infected but preventing you from infecting other people; similarly, with the use of insect repellants.
The Member also asked a question on the use of fogging. We do not believe in fogging as a first-line of defence.
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Study after study has found that source eradication of breeding areas is the most effective way of dealing with the problem. In extremely high risk areas where we think that there is a significant pool of adult mosquitoes which are infected, we would use fogging in a concentrated and targeted manner. Generalised fogging – where you see more smoke rather than real impact – is not something that I would recommend.
The question on ovitraps, we actually use that more as a surveillance because it will give us some idea of the prevalence of mosquitoes and whether those mosquitoes that we trap are infected with the dengue virus.
I just want to conclude that in fact, although we focus on mosquitoes, actually the real primary host for dengue is us, human beings. If you were a mosquito, your perspective would be that human beings are the problem. The human beings are the reservoir for the virus. Of course, we will take the human-centric point of view. I just want to emphasise: take all sensible measures to protect yourselves, your family and your neighbours; eliminate all breeding areas. If you have any doubts about your own potential to be infected, please do the responsible thing: Get yourself diagnosed and take appropriate measures to isolate yourself from your friends, families and neighbours with mosquito nets and repellents.
Mdm Speaker, the fight against dengue has been on-going for decades. So has the research on dengue vaccination. Can I ask the Minister if he has any update on dengue vaccination research?
I thought I will show this chart. It goes back to the 1960s. In the earlier years – in the 1960s and 1970s – there was very low incidence of dengue. It picked up mainly in the 1980s and 1990s. Before Members jump to the wrong conclusion and say that this is a Singapore problem, this is a global problem. For some reason which we still do not fully understand, there has been a global increase in dengue, particularly in areas of the world bounded by 35 degrees north and south of the Equator. Dr Lam is absolutely right. The only long-term resolution to this problem is a vaccine. There have been some trials going on, but I would say at this point in time, it is not yet ready to be rolled out on a full scale basis.
Basically, my strategy in Singapore is to keep buying us time; keep intensively eradicating mosquito breeding within our city; and then, if and when the vaccine is ready, we can embark on mass vaccination. At that point in time,
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NEA can redeploy the 1,000 inspectors who are currently knocking on doors every day, checking on mosquito breeding. I also want to make this point that I am very grateful to the residents and citizens of Singapore for cooperating with this effort and for their patience over these years. Once the vaccine is ready, we roll that out, and we build up immunity in our population, then this problem will be resolved.
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