Dengue Fever

Very useful information on Dengue fever from the Health Promotion Board of Singapore.

What is dengue fever?

Dengue fever is a viral infection that usually starts suddenly with a high fever. The person experiences:

• High, prolonged fever (usually lasts for 5 to 7 days)
• Rashes
• Severe headache
• Pain behind the eyes
• Muscle and joint pains
• Nausea
• Vomiting
• Loss of appetite
• Fatigue
• Diarrhoea

A rash usually appears three to four days after the start of the fever. There are three types of dengue rash. The most common is the petechial rash appearing as red dots on the skin. (Fig 1). The rashes are usually found on the limbs and is due to the bleeding under the skin.

Fig 1. Petechial rash

In the second type of rash, the whole skin becomes reddish with scattered, small areas of normal skin (Fig 2).

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Fig 2. Diffuse erythematous rash with areas of normal skin.

The last type of rash appears as red flat or raised leisons. There may be itching (Fig 3).

Fig 3. Maculopapular rash

(The above photos are courtesy of CDC, Tan Tock Seng Hospital, Singapore)

Severity of Dengue Fever/ Dengue Hemorrhagic Fever

The dengue virus has four strains called serotypes 1, 2, 3 and 4. Getting infected with one serotype does not protect you against the other serotypes. In fact, getting a second dengue infection, particularly with serotype 2, leads to an even worse infection such as Dengue Haemorrhagic Fever and Dengue Shock Syndrome which can be fatal.

With Dengue Hemorrhagic Fever, bleeding may occur from the nose, mouth, and gums. Bruises may appear and this can be a sign of bleeding inside the body. There are small red spots on the skin and the urine may contain blood.

Without prompt treatment, the person can go into shock, also known as "Dengue Shock Syndrome". Dengue Haemorrhagic Fever is fatal in about 5 percent of the cases, mostly among children and young adults.

What treatment can you get if you have dengue fever?

There is currently, no specific anti-viral drug to treat the disease nor is there a vaccine to prevent a person from being infected with the dengue virus. Rest and drinking lots of water to prevent dehydration will help. For severe headaches and body aches, a painkiller (such as acetaminophen) may help to reduce the discomfort. Daily blood tests may be necessary to monitor the risk of bleeding and in severe cases, blood and other fluid transfusions may be necessary. The illness can last up to 10 days, but complete recovery can take as long as a month.

The average medical cost for a patient admitted to hospital for dengue viral illness is between $1,500 and $3,000 (depending on ward class).

How is dengue fever spread?

Dengue Fever spreads through the bite of the Aedes mosquitoes.

The transmission cycle for dengue starts when:

• Infected Aedes mosquito bites a healthy person.
• 4-7 days later, the infected person develops fever (after the virus multiplies i.e., incubation period). The person usually then sees a doctor.
• When fever starts, the person becomes infectious for about 5 days.
• If an Aedes mosquito bites the person during this period when he is infectious, it will pick up the dengue virus in his blood.
• The virus takes 7-10 days to multiply in the second mosquito.
• The mosquito then becomes infective and the cycle starts again when it bites another person.

An infected person does not spread the virus to another person directly but he becomes a source of dengue virus for the Aedes mosquitoes.

How can you prevent being infected with the dengue virus?

To prevent dengue fever, you must prevent the breeding of its carrier, the Aedes mosquitoes, identified by their black and white stripes on the body (Fig 4). A puddle of water about the size and depth of 20-cent coin is sufficient for an Aedes mosquito to breed in.

Fig 4. Aedes mosquito	Fig 5. Aedes aegypti larva

The Aedes mosquitoes are commonly found breeding in clear stagnant water in flower vases, flower pot plates, roof gutters, earthen jars for water storage or decorative purposes, watering cans, and bamboo pole holders.

The Aedes mosquito can also breed in unusual places such as water trapped in the hardened soil in potted plates, and the rim of unwanted pails

Every other day

• Change water in flower vases.
• Scrub the inside of vase to remove mosquito eggs filling in fresh water.
• Remove water in plant pot plates.
• Scrub the plate thoroughly to remove mosquito eggs.
• Clear fallen leaves and stagnant water in drains and garden. Some leaves can collect water.

Once a month

• Add prescribed amounts of sand granular insecticide into containers, vases, gully traps and roof gutters, even if they are dry.

• Sand granular insecticide can be purchased from plant nurseries and DIY stores. (Caution: Do not add the chemical into drinking water. Keep out of reach of children.)
• Clear away leaves in roof gutters and apron drains. Remove roof gutters wherever feasible.

At all times

• Turn pails and watering cans over and store them under shelter. Place/ store all articles that can collect rain water under shelter at all times.
• Cover bamboo pole holders when they are not in use.
• Cover rarely used gully traps. If possible, replace gully trap covers with non-perforated ones and install anti-mosquito valves.
• Do not block the flow of water in scupper drains along common corridors in HDB estates. Do not place potted plants and other paraphernalia over the drains.
• Do not litter. Paper cups and water bottles thrown indiscriminately into drains, grass verges, roadside, vacant lands and other public places can collect rainwater and breed mosquitoes.
  

If you are vacating your home or away on long holiday

• Cover the toilet bowls.
• Seal off the overflow pipe of the flushing cistern.
• Cover all gully and floor traps.