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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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• 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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Regions with dengue fever

Dengue Fever 2001

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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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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.

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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 (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

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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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

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.

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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 0111Web site : www.cheu.gov.hk

• Food and Environmental Hygiene Department (about mosquito breeding)Hotline : 2868 0000Web site : www.info.gov.hk/fehd

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Let’s remove stagnant water

and eliminate mosquitoes