Japanese encephalitis Cause & prevention

1. Japanese encephalitis Cause & prevention Department of Health Hong Kong SAR

2. 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

3. Distribution of Japanese encephalitis in Asia

4. Japanese encephalitis in Hong Kong • Uncommon, & • Not endemic in Hong Kong

5. Transmission 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

6. Symptoms 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.

7. Treatment • No effective specific treatment available • Supportive treatment only

8. Prevention • Personal protective measures and mosquito elimination are the most important • travellers going to endemic areas may consider vaccination

9. Prevention ofMosquito 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-containingmosquito-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%

10. Prevention 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

11. 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 breeding

12. 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 breeding

13. JE Vaccination • Prevent encephalitis from JE virus • Recommended for use in endemic areas

14. Adverse 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

15. Contraindictions for JE vaccination • History of previous severe allergic reaction • Infant< 1yr of age • Pregnancy

16. 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

17. See 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

18. Health 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