Dengue in Singapore: guide to symptoms, prevention and cure

Dengue facts, stats, strains, vaccines, symptoms and preventions

Singapore is one of the world’s safest cities, but we’re still not safe from Dengue fever. This tropical disease may be deadly, particularly for young kids, but knowledge is power. With reports from the National Environment Agency of a spike in Dengue outbreaks in Singapore (554 cases were reported during the week ending 9 January 2016 – 96 cases more than the previous week), we decided to hunt down some facts, a few tips, and one kick-a*** solution (scroll to bottom), so you can take the sting out of this insect infestation and turn it into a manageable situation. Check out our diary of a Dengue fever attack for an inside account on the symptoms and recovery!

1. Mosquitoes that carry Dengue

The breed that is most responsible for the spread of Dengue are infected adult Aedes aegypti mosquitoes. Their population has doubled in Singapore since May 2014. They are black with white stripes on their body and legs. It’s the females that bite as they use blood to enable egg production. But let’s face it, if you’re close enough to see their colouring and sex you could be close to being a victim. It’s best to defend yourself against all mosquitoes and take preventative measures to avoid bites. Most importantly, people who acquire Dengue Fever need to prevent successive bites – if a mosquito that does not carry Dengue bites an infected person and acquires the virus, they can become a carrier. And this is where the spread of Dengue really gains momentum.

2. Behaviour of Dengue-carrying mosquitoes

As if you didn’t already have ankle-biters to worry about – the Aedes aegypti mosquito is quite partial to biting around the feet too. Unfortunately, this can take place at any time of the day but peak hours are a couple of hours after sunrise and before sunset. They’re considered a domestic insect because they like hanging out indoors near humans. When resting, they are quite fond of dark and shady places like behind curtains, in wardrobes, under furniture and in corners. They like to breed in water so places where water is stagnant and can collect is the ideal home for larvae. Given the right condtions, an Aedes mosquito can hatch into larva in less than a day. By the same token, an egg can lay dormant for 9 months in dry conditions and hatch when conditions are right again. The larva then takes about four days to develop into a pupa, and another two days to mature into an adult. Three days after the mosquito has bitten a person and taken in blood, it will lay eggs, about 100 of them, and the cycle begins again. This mosquito can lay eggs 3 times in its lifetime and its lifespan is about 2 weeks. If the mosquito happens to contract Dengue by biting an infected person then the results of this rapid breeding are dire.

3. Different strains of Dengue

There are 4 different strains or serotypes of Dengue and currently three of them are active in Singapore. This is a rare occurrence and a big reason why cases of infection have increased. Den-2 had been the main culprit for the spread of the disease for a while but just like an ageing rock band that won’t die, Den-1 and Den-3 have recently had resurgence. This means that past sufferers, that would usually help to arrest the disease due to their increased immunity, have little defence against these previously dormant strains.

4. Dengue at its peak

Mosquitoes like to make hay when the sun shines. The hot dry months of May to October, in Singapore, are typically when Dengue cases are more prevalent. The mosquitoes can breed and mature unimpeded at an accelerated pace. What makes this year a bit more concerning is that Dengue epidemics tend to occur every 5 to 7 years, with higher peaks recorded each time it returns, and we are now due to ride the crest of this wave. Although the number of people infected currently is significant, the number of people experiencing severe fever is considered low.

5. Trial of Dengue vaccine

The results of a trial of the world’s first Dengue vaccine have shown it capable of providing moderate protection against 3 strains of Dengue, according to findings published by The Lancet Journal. The study found the vaccine reduced the most serious cases of haemorrhagic fever by nearly 90 percent. However, protection for children did not prove very effective and it did not fare well against Den-2, our most common strain in Singapore. The results suggest the new vaccine acts best as an immune booster for patients with some previous exposure to the virus. It’s a safe 3-part does but its still undergoing trials by its French producer, Sanofi, and it remains to be seen if it becomes available in Singapore and what the cost might be.

6. Symptoms of Dengue Fever

The Dengue Virus is a mean little infectious agent and takes 2 forms. Dengue Fever is the less vicious attacker but is no walk in the park. Symptoms include a fever that can last 7 days, body aches and joint pain (which is where its other name, Breakbone, comes from), intense headaches, vomiting, nausea, loss of appetite, dehydration, itching and skin rashes. Even when a sufferer is past the worst of it, it can take a month to recover from tiredness and being rundown. Dengue Haemorrhagic Fever shares all the same features with the addition of a severe reduction in platelet count, blood vessel leakage, bleeding of the gums, nose, skin and internal organs and dangerously low blood pressure. Needless to say this can be life threatening and treatment should be sought immediately.

7. Treatment for Dengue Fever

It’s important to visit a GP for diagnosis, then rest and drink plenty of water. A doctor should also be able to instruct if hospitalization needs to take place. If symptoms already include stomach pain and vomiting, head to the hospital. There are no anti-viral drugs available but there a few things that doctors might prescribe to ease symptoms such as folic acid for stomach bleeding and antihistamines for itchy skin. If dehydration is very bad then intravenous fluids will need to be administered. If platelet count gets very low then there might be a need for blood transfusions.

8. Preventing Dengue infection

Prevention is the cure for now. Here’s what you can do:

Do the NEA 5 step Mozzie Wipeout
*Change water in vases/bowls on alternate days
* Turn over all water storage containers
* Cover bamboo pole holders when not in use
* Clear blockages and put BTI insecticide in roof gutters monthly
* Remove water from flower pot plates on alternate days
* Refer to their checklist for houses and HDB’s/condos

Contact the NEA
We’ve had first hand experience dealing with these guys and can’t speak of them highly enough. After sending off an email to inform that there seemed to be a few more mozzies in our area than normal, the NEA had contacted us and deployed a crew to our home within 24 hours. An extremely thorough inspection was carried out and neighbouring properties were also visited. Some traps consisting of carbon dioxide tablets, designed to attract and kill mosquitoes were inserted into drains for good measure. We even got a follow up call a few days later to say they had discovered a breeding ground nearby and had destroyed it. So, big thumbs up NEA!

Apply insect repellent
* DEET – The most common active ingredient for repellents in Singapore is DEET, in concentrations from 7% to 25%. Typically a higher concentration indicates longer-lasting protection, not a reduction in your chances of being bitten. Studies suggest it is safe for children in lower concentrations but not for infants under 2 months of age. A reliable option is the RID range from Australia available at International Medical Clinic. IMC carries the Tropical Strength range (6 hours protection), the low irritant Kids RID which is suitable for children over 6 months of age (2 hours protection), and an SPF 30+ sun screen repellent combination.
* Permethrin – Permethrin is a naturally occurring insecticide which can be used safely to treat your baby clothes and it’s a good option for children under 6 months old. IMC stock Permethrin Treatment Kits.
* Natural – There are a number of natural alternatives available. Products that contain citronella, such as Badger Anti-Bug Balm, have shown to be effective and are safe to use all over the body. You will need to re-apply more often though.
For more product options check out the selection at Redmart.

Burn citronella oil
Burning candles containing citronella can reduce the chance of being bitten somewhat. In fact, any candle may help because partly what the mosquito is avoiding is the smoke, not just the citronella. You do need to be safety-conscious though – effectiveness improves the closer you are to the flame and smoke. We really like these clean-burning and soot-free soy citronella candles from Verandah Living that have over 100 hours burn time. You can also pick up citronella essential oil from iherb if you prefer to use a burner. Mosquito coils are considered questionable due to the fact that the smoke they produce, from sometimes-unregulated ingredients, can be harmful to respiratory function.

Use mosquito nets
Although a mosquito net might not be that useful at night, it’s a good option for protecting sleeping babies during the day when Aedes aegypti mosquitoes are out feeding. It’s worth noting though that there are some safety risks involved: IKEA withdrew their netted bed canopies for children recently amid fears of strangulation. Spotlight sell bed canopies and mosquito nets and The Australian Mosquito Net Shop, who ship internationally, have a model that fits over cots and can then be suspended to extend over beds as children grow.

Try fogging
If you live in a condo, this probably already takes place once a week. If you live in a house you can organize to have it done but it’s really only effective if it takes place on an ongoing basis due to the lifecycle of the mosquito. There is a lot of controversy surrounding fogging and DDT due to the side effects of insecticides and diesel and the negative effect they can have on the environment.

Research mosquito traps
Mosquitoes are attracted by sight and smell, so lights and carbon dioxide are the common lures used to trap them. Because the Aedes aegypti mosquito is active during the day, they are quite responsive to visual attractants. Most traps you can buy use a combination of both of these elements and when the mosquito gets close a fan sucks them in and catches them in basins, sticky mats or bags. Generally it can take about 2 months to wipe out enough females for the local population to collapse. The principle behind a trap is to act as a screen, so their placement is crucial. They need to be positioned between the source of mosquitoes and where people gather. The effectiveness of them is therefore debatable – they will certainly kill the ones that they trap but the issue is getting them to the trap site. Online reviews point to the Mega Catch Ultra as the most effective trap on the market currently. You can source them from Mosquito Management System here in Singapore. In our experience, the options you can get at HomeFix and other small hardware stores baffled us as the store staff don’t seem to be that informed about the products. One last thing on traps: the internet is awash with home made mosquito trap guides, but because liquid is usually involved be careful you don’t go causing an infestation rather than preventing one.

The Weapon of Mosquito Destruction! This is our favourite option. If only it were available. In a crazy turn of events, astrophysicist Lowell Wood, one of the architects of the Regan era Star Wars programme has turned his laser killing technology from Soviet rockets to insects! At the request of The Bill and Melinda Gates Foundation, he designed a device that could annihilate malaria called the photonic fence. It consists of infrared LED lamps on fence posts that create and reflect a field of light. Charged coupled devices, like those found in cameras detect shadows in the light and a non-lethal laser can be fired off to source data on the object. A custom-image processing board (not sure what that bit is) determines that the object matches the description of an offending mosquito (right down to wing beat patterns), a safety check can be carried out and then a lethal laser fires to stop the mosquito dead. It’s thought this solution could be deployed around schools, hospitals and even villages. While it hasn’t taken off to combat malaria in Africa as yet, due to consistent electricity issues it would seem, we reckon it could be worth investigating how to apply this sci-fi solution to our Dengue carrying mosquito population here in Singapore.

More information
If you have concerns about an infestation in your area or want to check the current red zones (hot spots) where Dengue is prevalent you can check the NEA website. You can also find more info on Mosquito World.