Dengue fever is a mosquito-borne viral disease transmitted by Aedes aegypti and Aedes albopictus mosquitoes. It causes high fever, severe headache, pain behind the eyes, muscle and joint pain. There is no vaccine or specific treatment, but prevention focuses on eliminating mosquito breeding sites by removing stagnant water and protecting against mosquito bites. The document provides information on the transmission, symptoms, treatment and prevention of dengue fever, with a focus on the situation in Hong Kong. It emphasizes the importance of community involvement to eliminate mosquitoes and their breeding sites.
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What is it?
Mode of transmission
Symptoms and treatment
Prevention
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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• 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
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The Situation in Hong Kong (1)
• 11 cases in 2000
• 17 cases in 2001
• First local case identified in September 2002
Imported cases
Mosquito elimination has
become an imminent
matter.
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The Situation in Hong Kong (2)
The Department of Health is working
closely with other government
departments to monitor the spread of
dengue fever in Hong Kong. Prompt
measures to prevent and control the
spread of the disease have been put
in place.
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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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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.
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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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Symptoms of
Classical Dengue (1)
• 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 (2)
•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.
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Treatment (1)
• 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 (2)
• Wiping the body with warm
water and proper use of
anti-fever drugs that can
relieve the fever.
• Don’t take aspirin-
containing drugs because
they worsen the
haemorrhage.
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Protect Yourself against
Dengue Fever
As yet, there is no effective vaccine against
dengue fever. Therefore, the best prevention is
to avoid being bitten by mosquitoes by paying
attention to the following:
•Avoid staying in dark, outdoor places such as
brushwood, pavilions or the shade of a tree
during the hours when Aedes albopictus is
active.
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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
•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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Elimination of Mosquitoes
The most effective way
to eliminate
mosquitoes is to
keep the environment
clean and to remove
stagnant water so that
mosquitoes can’t
breed.
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Possible Breeding Grounds of
Aedes Albopictus (1)
Artificial containers:
Vases, saucers underneath flower
pots, trays underneath air-
conditioners, buckets, jars and jugs of
earthenware, cement troughs, dumped
tyres and solid wastes such as cans,
disposable cups and bowls, and plastic
bags.
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Possible Breeding Grounds of
Aedes Albopictus (2)
Natural containers:
The hollow space inside a bamboo,
hollows of a tree and the rachis of a
leaf.
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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
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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.
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The school is an ideal setting for
health promotion.
Targets: all staff, students and
parents.
• Enhance their understanding of mosquito-borne
diseases.
• Raise their awareness of dengue fever and evaluate
the risks of it.
• Encourage members of the whole school to play an
active part in mosquito elimination.
• Eliminate black spots of mosquito breeding.
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Black Spots of Mosquito
Breeding in the Campus
• Garden / gardening corner / saucers
underneath flower pots / aquatic
plants
• Tuckshop
• Rubbish collection stations
• Ditches
• Toilets
• Water tanks / pools
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Eliminate mosquitoes:
• Planning, manpower arrangement,
areas to be inspected, inspection
time and record
• Please call the Food and
Environmental Hygiene Department’s
hotline for assistance if required:
2868 0000
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Mosquito Elimination
Checklist (1)
• Are containers and other items where
water could accumulate disposed of
properly?
(For example, throwing empty cans,
foam rubber boxes, cups and bottles
into a covered bin.)
• Are water containers covered properly?
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Mosquito Elimination
Checklist (2)
• Are ditches free from blockage?
• Are containers with stagnant water
cleaned regularly?
(For example, vases, saucers underneath
flower pots, water storage device of an air-
conditioner, water tanks and pools.)
• Are uneven ground surfaces filled to
prevent the accumulation of stagnant
water?
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See Doctor Immediately
•Having been bitten by
a mosquito and
displaying symptoms
of dengue fever
afterwards
•Falling ill, especially
having a fever within
one month after you
have returned from
abroad
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If you suspect that you have
dengue fever, the most
important thing to do is to
see a doctor.
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Hotline / Web siteHotline / Web site
• Central Health Education Unit, Department
of Health
Hotline : 2833 0111
Web site : www.cheu.gov.hk
• Food and Environmental Hygiene
Department (about mosquito breeding)
Hotline : 2868 0000
Web site : www.info.gov.hk/fehd