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Imported case of Japanese encephalitis under CHP investigation

     The Centre for Health Protection (CHP) of the Department of Health (DH) is today (November 7) investigating an imported case of Japanese encephalitis (JE) affecting a man aged 23 and hence urged the public to take precautions against mosquito-transmitted diseases.

     The patient, with good past health, developed fever and headache on October 28 and sought medical attention from North Lantau Hospital on October 31 and was transferred to Princess Margaret Hospital on the same day. He is currently admitted to the Intensive Care Unit for further management in critical condition.

     His paired serum samples showed more than four-fold rise in antibody titres against JE, a viral disease transmitted by the bite of infective mosquitoes, by the Public Health Laboratory Services Branch of the CHP.

     Initial enquiries by the CHP revealed that the patient, who lives in rural area of Thailand, had travelled alone and arrived Hong Kong on October 24. His home contact has remained asymptomatic so far. Investigations are proceeding.

     Including the above case, to date, six JE cases (two local, three imported and one is still under investigation) have been reported to the CHP this year. Three cases (two imported and one local) were reported in 2012 while one (local) was filed in 2011. Locally, no cases were reported from 2008 to 2010.

     A spokesman for the CHP explained that JE is a viral disease transmitted by the bite of infected mosquitoes. Culex tritaeniorhynchus (Culicine mosquito) is the principal vector of JE and is nocturnal. It mainly breeds in waterlogged fields, marshes, ditches and small stagnant collections of water around cultivated fields. The mosquitoes become infected by feeding on pigs and wild birds infected with the JE virus, and then transmit the virus to humans and animals during the feeding process. JE is endemic in the Mainland and Southeast Asia.

     Most JE virus infections are mild without apparent symptoms other than fever with headache. More severe infections are clinically characterised by quick onset of headache, high fever, neck stiffness, impaired mental state, coma, tremors, occasional convulsions (especially in infants) and paralysis.

     To prevent contracting JE, members of the public, particularly those living in rural areas, are reminded to take heed of the following preventive measures, especially after dark:

* Wear long-sleeved clothes and trousers;
* Use effective insect repellents containing DEET over exposed parts of the body when outdoors; and
* Use mosquito screens or nets in rooms which are not air-conditioned.

     Travellers to endemic areas of JE should take the following precautions:

* Avoid outdoor exposure to mosquito bites at dusk and dawn, especially in rural areas, when mosquitoes spreading this virus are most active;
* Apply effective insect repellents containing DEET over exposed parts of the body and clothes; and
* Consider vaccination that should be completed at least 10 days before departure to endemic areas in Asia or the Western Pacific for staying over one month, particularly in high-risk rural areas.

     The public may visit the CHP's website ( for more information on JE and that of the DH's Travel Health Service ( for further information on JE vaccination and outbreaks in other areas.

Ends/Thursday, November 7, 2013
Issued at HKT 20:10


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