Dengue fever is an illness caused by the dengue fever virus which can be transmitted to humans by the bite of an infected Aedes mosquito. Aedes aegypti mosquitoes (which have black and white stripes on their legs) occur commonly in Singapore and carry the virus that causes Dengue fever. These mosquitoes tend to live in urban areas and will bite during the day, particularly at dawn and dusk. They breed in stagnant water around the home.
There are 4 strains of dengue viruses. Infection with one strain will provide protection against only that particular strain. Future infection by other strains is possible.
Dengue fever cannot be spread directly from person to person.
The incubation period of dengue fever normally ranges from between 3 to 14 days. After the person is infected with the virus, there is generally an average of 4-7 days before the onset of symptoms.
Symptoms typically include sudden onset of fever, (which can last up to 7 days) which may be accompanied by headache (often behind the eyes), body aches, joint pains, loss of appetite, nausea, vomiting and the development of skin rashes. A blood test can diagnose Dengue fever and will often show low platelets (the clotting particles in the blood).
Dengue haemorrhagic fever presents in a similar way to dengue fever but is associated with more severe bleeding problems (such as bruising, bleeding from the gums or nose and bleeding into the skin and internal organs). It can be fatal if unrecognised or not treated.
You need to see your doctor immediately if you have bleeding complications such as bruising, nose bleeds or bleeding from the gums or bowel.
Dengue infection without obvious symptoms may occur and tends to occur more frequently in children. Dengue infection in adults is more likely to be symptomatic.
There is no specific treatment for dengue fever or dengue haemorrhagic fever. Treatment involves treating the fever and other symptoms with paracetamol, rest and lots of fluids. Avoid aspirin and ibuprofen (Nurofen) which may increase the risk of bleeding.
In severe cases, supportive care with intravenous fluids and frequent blood test monitoring in hospital reduces the risk of complications of the disease. In severe cases, blood transfusions may be required.
Dengue fever can be prevented by avoiding mosquito bites and reducing mosquito breeding around the home.
To avoid being bitten by the mosquitoes:
- Wear light coloured clothing, with long sleeves and long trousers
- Avoid using perfume and after-shave lotion when outdoors
- Use an insect repellent containing DEET on exposed skin and apply it regularly, especially on the ankles and feet. A formulation containing 30% DEET provides up to 6 hours protection
- Keep in mind that an insect repellent with a higher DEET concentration does not provide better protection than those with a lower concentration, they simply last longer
- Although DEET toxicity is very rare, to reduce the risk, use just enough repellent to cover exposed skin and if possible use one with a lower concentration (although do note that if you are out for many hours, then this may need to be reapplied). For reference, a 6% DEET concentration will provide protection for about 2 hours and 20% for about 4 hours. Concentrations above 50% do not provide any increase in protection time
- For children, use repellents with a lower DEET concentration (less than 30%) and do not use at all for children under 2 months of age
- If applying sunscreen, apply the DEET repellent after the sunscreen
- Stay in accommodation with insect screens on the windows
- Use air conditioning as it is a deterrent to mosquitoes
- Use mosquito nets (checks for holes before use) when there are no insect screens
- Use a knock down spray (fly and insect spray) in your room at night e.g. before you go out for dinner, if your accommodation doesn’t have window screens or air conditioning.
DEET is an insect repellent which should be applied to intact (non-broken) skin which is exposed (not covered by clothing) and it should not be applied near the eyes. To apply to the face, spray onto the hands and apply carefully to the face, avoiding the eyes. Do not spray DEET insect repellents directly onto the face.
DEET can be used in pregnancy, however it is recommended that applications be kept to a minimum.
There have been cases of toxicity from DEET in children where there have been frequent, heavy, whole body applications of DEET. DEET should not be applied to the hands of young children as hands could end up in the mouth or rubbing the eyes.
After returning indoors, the skin should be washed with soap and water.
Mosquito patches containing citronella oil may be effective for small children.
Around the house, good daily habits such as clearing roof gutters, clearing leaves and stagnant water from drains, removing water from potted plants daily, avoiding the use of plates under potted plants and changing the water in vases everyday will also help to eliminate the chances of mosquito breeding.
For more details about Dengue clusters: http://www.dengue.gov.sg/subject.asp?id=74