Press Release

CHP investigates first case of Japanese encephalitis in 2015

30 June 2015

The Controller of the Centre for Health Protection (CHP) of the Department of Health (DH), Dr Leung Ting-hung, today (June 30) announced the investigation into the first suspected local case of Japanese encephalitis (JE) this year, and hence again urged the public to maintain strict environmental hygiene, mosquito control and personal protective measures both locally and during travel.

"Although the case had travel history during the incubation period, the duration of stay was short. It cannot be ruled out that the case was locally acquired at this stage. As a precautionary measure, we are working closely with the Food and Environmental Hygiene Department (FEHD) to assess and prevent any possible spread of infection," Dr Leung said at a briefing today.

According to the patient's family, the male patient, aged 68 with underlying illness, developed fever and poor appetite on June 23 and acute confusion on June 24. He was then taken to Ha Kwai Chung General Out-patient Clinic for medical attention and was transferred and admitted to Princess Margaret Hospital for further management. He is now in the Intensive Care Unit in critical condition.

Both his cerebrospinal fluid and blood sample tested positive for antibodies against JE upon testing by the CHP's Public Health Laboratory Services Branch.

Initial enquiries revealed that, according to his family, he had travelled to Kaiping and Xinhui, Guangdong, on June 11 and returned to Hong Kong on June 12. His home contacts have remained asymptomatic and have been put under medical surveillance. The CHP is conducting further enquiries for more information on his travel history, local movements and exposure.

In addition, the patient lives in Wah Yuen Chuen, 12 Wah King Hill Road, Kwai Chung. According to the FEHD, there are water streams and water bodies in the vicinity, while according to Agriculture, Fisheries and Conservation Department (AFCD), there are wild birds in the area but there are no records of wild pigs or registered pig farms nearby.

"Upon notification and laboratory confirmation, the CHP immediately commenced epidemiological investigations and promptly informed the FEHD and the AFCD for vector investigation. We also informed the relevant management office and the Home Affairs Department for their follow-up. Investigations and health education in the vicinity where the patient frequented are proceeding," Dr Leung added.

Officers of the CHP will conduct a site visit and field investigation by questionnaire surveys at the patient's residence for active case finding and arranging blood tests. Joint health talks with the FEHD will be held to deliver health advice to residents and the public.

Persons who have been to the vicinity of Wah Yuen Chuen with JE symptoms should call the CHP's hotline (2125 1133) for laboratory investigation or referral to hospital as appropriate. It will operate until 10pm today and from 9am to 6pm tomorrow (July 1).

"We will issue letters to doctors and hospitals to alert them to the case," Dr Leung said.

This is the first JE case reported to the CHP this year. Five cases (three local, two imported) were filed in 2014 while six (two local, three imported, one unclassified) were filed in 2013.

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 on the Mainland and in Southeast Asia.

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

To avoid 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 loose, light-coloured, long-sleeved clothes and trousers;
• Use effective insect repellents containing DEET over exposed parts of the body and clothing 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 and arrange a travel health consultation with a doctor to determine the need for vaccination and vector preventive measures at least six weeks before departure to endemic areas in Asia or the Western Pacific for stays of over one month, particularly in high-risk rural areas.

The public may visit the pages below for more information:

• The CHP's JE page (This link will open in a new windowwww.chp.gov.hk/en/content/9/24/28.html);
• The DH's Travel Health Service (This link will open in a new windowwww.travelhealth.gov.hk);
• The CHP's tips for using insect repellents (This link will open in a new windowwww.chp.gov.hk/en/view_content/38927.html);
• The CHP Facebook Page (This link will open in a new windowwww.fb.com/CentreforHealthProtection);
• The CHP YouTube Channel (This link will open in a new windowwww.youtube.com/c/ChpGovHkChannel); and
• The FEHD's Guidebook on Control and Prevention of Mosquito Breeding (This link will open in a new windowwww.fehd.gov.hk/english/safefood/handbook_prev_mos_breeding.html).