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2. 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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3. 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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4. Aedes mosquito
Aedes Aegypti
Aedes Albopictus
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5. Vector
Aedes
albopictus
The life cycle of a vector mosquito is divided
into the 4 stages: egg, larva, pupa and adult
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6. 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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7. 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.
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8. 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.

9. The Situation Worldwide
• About 50 million cases annually
worldwide
• Incidence of dengue fever highest in
tropical and subtropical regions
• Recent increase in disease activity
worldwide
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10. Dengue Fever 2001
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Regions with dengue fever

11. 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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12. Transmission
Infected
mosquito
Healthy person
Incubation Period: 3 to 14 days
Most commonly 4 to 7 days
Infected
person
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