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Japanese encephalitis Japanese encephalitis Cause & preventionCause & prevention

Department of HealthDepartment of Health

Hong Kong SARHong Kong SAR

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Japanese Encephalitis (JE)Japanese Encephalitis (JE)• Leading cause of viral encephalitis in Asia• 30-50,000 cases annually• Case-fatality 5% to 35%• Transmitted by bite from mosquito

• Occur all year round

• High risk:– After rainy season

– Migratory bird pattern

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Distribution of Japanese encephalitis in AsiaDistribution of Japanese encephalitis in Asia

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Japanese encephalitis in Hong KongJapanese encephalitis in Hong Kong

• Uncommon, &

• Not endemic in Hong Kong

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Transmission of JE serogroup virusesTransmission of JE serogroup viruses

• Transmitted by rice field breeding mosquitoes, mainly Culex tritaeniorhychus

• mosquitoes infected by feeding on infected pigs and wild birds (amplifying hosts)

• Human as dead end hosts• No person-person or animal-person

transmission

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Symptoms of JE infectionSymptoms of JE infection• Most cases asymptomatic• Incubation 4 to 14 days.• Mild -fever with headache• Severe infection

– quick onset– headache & high fever– neck stiffness, – stupor, disorientation, – coma, tremors, – occasional convulsions (especially in infants) and

spastic (but rarely flaccid) paralysis.

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TreatmentTreatment

• No effective specific treatment available

• Supportive treatment only

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PreventionPrevention

• Personal protective measures and mosquito elimination are the most important

• travellers going to endemic areas may consider vaccination

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Prevention of Mosquito BitesPrevention of Mosquito Bites

•Avoid going to rural area during dusk and dawn when the mosquitoes are most active

•Wear light-coloured, long-sleeved clothing and trousers

•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 BitesPrevention of Mosquito Bites

• Place of accommodation should have air-conditioners or mosquito nets; or

• hang mosquito screens around your bed, use insecticides or coil incenses to repel mosquitoes•Install mosquito nets to doors and windows so that mosquitoes can’t get in

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• Put all used cans and bottles into covered dustbins

• Change water for plants at least once a week, leaving no water in the saucers underneath flower pots

Prevent mosquito breedingPrevent mosquito breeding

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• Keep all drains free from blockage

• Cover tightly all water containers, wells and water storage tanks

• Top up all defective ground surfacers to prevent the accumulation of stagnant water

Prevent mosquito breedingPrevent mosquito breeding

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JE VaccinationJE Vaccination

• Prevent encephalitis from JE virus

• Recommended for use in endemic areas

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Adverse effects of vaccinationAdverse effects of vaccination

• 20% of the vaccinees will have tenderness, redness, swelling over the injection site

• Hypersensitivity reactions:Allergic reactions in 0.6% of Western adults

• Encephalitis & encephalopathy– Rare but severe neurological side effects– ~1 to 2.3 per million vaccinees

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Contraindictions for JE vaccinationContraindictions for JE vaccination

• History of previous severe allergic reaction

• Infant< 1yr of age

• Pregnancy

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Do I need to be vaccinated?Do I need to be vaccinated?

• Current recommendations:– Travellers going to endemic areas in Asia or Western

Pacific and staying over one month (particularly in high risk rural areas)

• Where can I have the vaccination?– Hong Kong Traveller’s Health Service of the Department

of Health– Enquiry: 2150 7235

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See Doctor ImmediatelySee Doctor Immediately•Having been bitten by a mosquito and displaying symptoms of JE afterwards

•Falling ill, especially having a fever within one month after you have returned from abroad

•Tell your doctor where you have been

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Health Information Hotline / Web siteHealth Information Hotline / Web site• Central Health Education Unit, DH

Hotline : 2833 0111Web site : www.cheu.gov.hk

• Travel Health Website, DH (on personal protection against mosquito bites & JE vaccination)Web site : www.info.gov.hk/trhealth/c_HKTHS.htm

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