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What is it?Mode of transmissionSymptoms and treatmentPrevention

Dengue Fever

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What is Dengue Fever?• Dengue fever, also know as

breakbone fever, is an acute communicable disease caused by virus.

• Infectious agent: Dengue viruses (categorize into types 1,2,3,4)

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Vectors of Dengue Fever• Aedes aegypti • Aedes albopictus

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Vector

Aedes albopictus

The life cycle of a vector mosquito is dividedinto the 4 stages: egg, larva, pupa and adult

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Mode of Transmission • A healthy person gets the disease when he is

bitten by an infected mosquito. The virus enters his blood from the mosquito’s saliva.

• An infected person could transmit the virus to mosquitoes if he is bitten by a mosquito anytime from the onset to the subsidence of the fever (a period of about 6 to 7 days). The disease is then spread by mosquitoes.

• Dengue fever is not spread by contact with infected persons.

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Transmission

Infected person

Healthy person

Infected mosquito

Incubation Period: 3 to 14 daysMost commonly 4 to 7 days

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Types

Classicaldengue

Denguehaemorrhagic

fever

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Symptoms of Classical Dengue

• Fever: continuous for 3 to 5 days

• Severe headache

• Painful limbs, joint pain, muscle pain, back pain, pain behind eyeballs

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Symptoms of Classical Dengue

•Rash appears on the 3rd to 4th day after onset. •Nausea, vomiting.•Slight gum bleeding and nasal bleeding.•Extreme fatigue and depression may follow recovery.• In very rare cases, the condition may worsen

into dengue haemorrhagic fever, leading to haemorrhage, shock or even death.

WHO GRADING OF DHF• Grade 1: fever, positive hess test• Grade 2: features of grade 1+ spontaneous

bleeding into skin or from other sites• Grade 3: circulatory failure manifested by

rapid week pulse, hypotension or low pulse pressure, cold and clamy skin, restlessness

• Grade 4: profound shock manifested by unrecordable BP and pulse

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Treatment • At present, there is no drug that

can treat dengue fever effectively. Patients infected with classical dengue usually recovers in 1 to 2 weeks.

• For serious cases, supportive treatments are provided by hospitals.

• If you suspect that you have dengue fever, you should seek medical treatment promptly.

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Treatment • Wiping the body with warm

water and proper use of anti-pyretic drugs that can relieve the fever.

• Don’t take aspirin-containing drugs because they worsen the haemorrhage.

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Control the Spread of Dengue Fever

Prevent the patient from being bitten by mosquitoes.

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Prevention of Mosquito Bites

Avoid going out in the hours when Aedes albopictus feed or wear light-coloured, long-sleeved clothing and trousers.

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Prevention of Mosquito Bites

•Apply DEET-containing mosquito-repellents over exposed parts of the body and clothes every 4 to 6 hours.

•For DEET products used by children, its concentration should be less than 10%.

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Prevention of Mosquito Bites

Your place of accommodation should have air-conditioners or mosquito nets. Otherwise, hang mosquito screens around your bed, use insecticides or coil incenses to repel mosquitoes.

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Prevention of Mosquito Bites

Install mosquito nets to doors and windows so that mosquitoes can’t get in.

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Elimination of Mosquitoes

The most effective way to eliminate mosquitoes is tokeep the environment clean and to remove stagnant water so that mosquitoes can’t breed.

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Elimination of Mosquitoes

Cover water containers tightly so that mosquitoes can’t get in to lay eggs.

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Elimination of Mosquitoes

• Dispose of domestic wastes properly to prevent the accumulation of stagnant water.

• Dispose of empty bottles, cans and lunchboxes properly, such as into a covered bin.

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Elimination of Mosquitoes•Change water for vases and aquatic plants at least once a week, leaving no water under

the pots or in the bottom saucers.

•Scrub the container surfaces thoroughly to prevent mosquito eggs

sticking on them.

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Elimination of Mosquitoes

Remove or puncture any dumped tyres to prevent the accumulation of stagnant water.

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Elimination of Mosquitoes

Ditches should be free from blockage.

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Elimination of Mosquitoes

Fill up uneven ground surfaces to prevent the accumulation of stagnant water.

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Elimination of Mosquitoes

Remove stagnant water immediately if mosquitoes are found to be breeding. Use environmentally friendly insecticides such as lavicidal oil if necessary.

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Elimination of Mosquitoes

In cultivation ponds, water tanks or large containers, biological controls such as keeping fishes to eat mosquito larvae would be a good option.