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Additional case of Japanese encephalitis under CHP investigation

     The Centre for Health Protection (CHP) of the Department of Health (DH) is today (July 18) investigating an additional confirmed case of Japanese encephalitis (JE) affecting a 52-year-old man and hence urged the public to take precautions against mosquito-transmitted diseases.

     The 52-year-old male patient, with good past health, presented with headache and fever on July 13. He was admitted to Tuen Mun Hospital on July 15 because of acute confusion. He is now in critical condition.

     Upon laboratory testing, both his serum and cerebrospinal fluid samples tested positive for antibodies against JE. JE is a viral disease transmitted by the bite of infected mosquitoes.

     The patient lives in Tin Shui Wai. His home contacts remained asymptomatic and have been put under medical surveillance. The CHP's investigation is proceeding.

     This is the second JE case reported to the CHP this year. Three cases were reported in 2012 (including two imported cases and one local case) while one (a local case) was reported in 2011. Locally, no cases were reported from 2008 to 2010.

     Regarding the first confirmed case this year reported early this week, a CHP spokesman said that the 59-year-old male patient is still hospitalised in Tuen Mun Hospital. His current condition remains critical.

     "The latest investigation by the CHP revealed that the 59-year-old male patient was in Hong Kong during most of the incubation period, the case was therefore classified as locally acquired,กจ the spokesman said.

     The CHP has been working closely with the Food and Environmental Hygiene Department (FEHD) and the Agriculture, Fisheries and Conservation Department (AFCD) to assess if there is any spread of the infection and to take necessary steps to contain infection and prevent spread.

     Upon receiving notifications from the CHP about confirmed cases of JE, the FEHD immediately carried out vector investigation among neighbours of the patient's residence in Yuen Long and strengthened the anti-mosquito measures in the public area thereat. Anti-mosquito measures have also been undertaken in the public area outside the pig farms in the vicinity of the patient's residence.

     Furthermore, the FEHD has collected specimens of Culex tritaeniorhynchus in the vicinity of the patient's residence and submitted them to the DH for examination for the JE virus.

     In addition to strengthening mosquito prevention work, the FEHD has also stepped up publicity via TV and Radio Announcement in the Public Interest as well as other publicity materials to remind the public to take appropriate precautionary and anti-mosquito measures to prevent the spread of mosquito-transmitted diseases.

     The AFCD identified four pig farms within two kilometres of the patient's residence. No abnormality was reported and the AFCD will step up surveillance. The AFCD will inform all pig farms in Hong Kong the recent case of human infections and urged them to carry out appropriate mosquito prevention and control measures.

     "Officers of the CHP had conducted home visits and surveys among neighbours of the patients' residences for active case finding and arranging blood tests. So far, 10 blood samples have been taken for laboratory testing. Two of these samples were tested negative and the other samples test results are pending," the spokesman said.

     "Up to 4.30pm today, the CHP hotline 2125 1122 has received 23 enquiries from members of the public since it was set up on July 16. The hotline operates from 9am to 9pm today and tomorrow, and then from 9am to 6pm till July 21," he added.

     Two health talks were delivered to provide the public with health advice. Two additional health talks will be held in Shun Tak Fraternal Association Wu Mien Tuen Primary School, Tin Shui Wai, at 2.30pm and in Tin Fai Road Community Hall, Tin Shui Wai, at 6.30pm tomorrow (July 19). Residents of Yuen Long District with JE symptoms are also advised to promptly seek medical attention.

     The CHP has issued a letter to all doctors to alert them about the latest information of Japanese encephalitis as well as to remind them to report any suspected cases to the DH for follow up.

     A CHP spokesman explained that 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, July 18, 2013
Issued at HKT 21:17


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