Dengue Fever What is it? Mode of transmission Symptoms and treatment Prevention

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)

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

Dengue Fever 2001 Regions with dengue fever

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.

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.

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.

Vector Aedes albopictus The life cycle of a vector mosquito is divided into the 4 stages: egg, larva, pupa and adult

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

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.

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.

Incubation Period: 3 to 14 days Most commonly 4 to 7 days Transmission 傳播途徑:登革熱病毒只能存在於人、猴及病媒蚊體內。 「登革熱」主要經由帶病毒蚊子(花腳蚊)，在叮咬人時，將病毒傳染給人。如果病者在剛發燒前至退燒期內(大約六至七日)被蚊叮，病毒也會傳給花腳蚊，成為帶病毒蚊子。毒蚊的傳染力可維持至其死為止，甚至經受感染的卵而傳給下一代(香港傳染病醫學會，1999)。不過與患者接觸是不會被傳染的。 Infected mosquito Healthy person Infected person Incubation Period: 3 to 14 days Most commonly 4 to 7 days

Types Classical dengue Dengue haemorrhagic fever

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

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.

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. 給予支緩性治療，登革熱患者要多休息、補充水份及按醫囑服藥，大約一個星期後就能逐漸康復，不會有後遺症；嚴重者或有出血傾向時則需要輸血或使用皮質類固醇。

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.

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.

Control the Spread of Dengue Fever Prevent the patient from being bitten by mosquitoes.

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

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%.

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.

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

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.

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.

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.

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

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.

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.

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

Elimination of Mosquitoes Ditches should be free from blockage.

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

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

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.

Prevention of Dengue Fever - A Whole School Approach 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.

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

Prevention of Dengue Fever - A Whole School Approach 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

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?

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?

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

If you suspect that you have dengue fever, the most important thing to do is to see a doctor.

Hotline / 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

Let’s remove stagnant water Prevention of Dengue Fever - A Whole School Approach Let’s remove stagnant water and eliminate mosquitoes