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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 aegypti is not found in Hong

Kong at present.• Aedes albopictus

- Aedes albopictus is very common in Hong Kong.

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Aedes mosquito

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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Habitual Behaviour of Aedes Albopictus (1)

• Usually breed in stagnant water

• Usually active in dark or shaded places outdoors, but indoor activity is also possible

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Habitual Behaviour of Aedes Albopictus (2)

• Female mosquitoes feed on human blood.

• They are most active 2 hours before sunset (around 5pm to 6pm) and at around 8am to 9am.

• Where do they sting?

Outdoors and indoors.

DO YOU KNOW…

• Dengue fever and dengue haemorrhagic fever are the most common mosquito-borne viral diseasein the world.•

• Only the female mosquito feeds on blood. This is because they need the protein found in blood to produce eggs. Male mosquitoes feed only on plant nectar.

• •The mosquito is attracted by the body odours, carbon dioxide and heatemitted from the animal or humans.

• •The female Aedesmosquito searches for suitable places to lay their eggs.

• •Aedes are day-biters, most active during dawn and dusk.

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• About 50 million cases annually worldwide

• Incidence of dengue fever highest in tropical and subtropical regions

• Recent increase in disease activity worldwide

The Situation Worldwide

10Regions with dengue fever

Dengue Fever 2001

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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