CHP investigates cluster of dengue fever involving imported cases

     The Centre for Health Protection (CHP) of the Department of Health is investigating today (December 7) a cluster of dengue fever (DF) involving two epidemiologically linked imported cases and again urged the public to maintain strict environmental hygiene, mosquito control and personal protective measures both locally and during travel.

     The first case involves a 16-year-old male patient announced earlier. He had good past health, who developed malaise, musculoskeletal pain and fever since November 29, and subsequently developed a rash over the chest and back. He attended Canossa Hospital on the same day and was admitted to Queen Mary Hospital on November 30. He is now in a stable condition and his blood sample tested positive for dengue virus upon laboratory testing.

     Initial enquiries revealed that the patient participated in a study tour in Thailand from November 19 to 24, and stayed at a rural resort. According to the patient, he went hiking in the forest and recalled mosquito bites there.

     The second case involves a 43-year-old male patient with good past health. He is the first patient's collateral of the study tour, who developed fever, myalgia and rash since November 26. He attended private out-patient clinics on November 28, December 3 and 4. He is now in a stable condition and his blood sample tested positive for dengue virus upon laboratory testing.

     The CHP conducted epidemiological investigations on other collaterals of the study tour. Initial enquiries revealed that three participants are symptomatic. Investigations are ongoing.

     The latest surveillance data shows that there is an increase in DF cases noted in some places in Asia (such as Bangladesh, Malaysia, Taiwan and Thailand) compared to the same period last year. Members of the public, while travelling abroad, should stay vigilant and carry out effective mosquito prevention and control measures. Detailed information on the latest DF situation in Hong Kong, as well as neighbouring and overseas countries and areas, has been uploaded to the CHP's website (

     "Apart from general measures, travellers returning from areas affected by DF should apply insect repellent for 14 days upon arrival in Hong Kong. If feeling unwell, seek medical advice promptly and provide travel details to the doctor," a spokesman for the CHP said.

     The public should take heed of the following advice on mosquito control:
  • Thoroughly check all gully traps, roof gutters, surface channels and drains to prevent blockage;
  • Scrub and clean drains and surface channels with an alkaline detergent compound at least once a week to remove any deposited mosquito eggs;
  • Properly dispose of refuse, such as soft drink cans, empty bottles and boxes, in covered litter containers;
  • Completely change the water of flowers and plants at least once a week. The use of saucers should be avoided if possible;
  • Level irregular ground surfaces before the rainy season;
  • Avoid staying in shrubby areas; and
  • Take personal protective measures such as wearing light-coloured long-sleeved clothes and trousers and apply insect repellent containing DEET to clothing or uncovered areas of the body when doing outdoor activities.

     DEET-containing insect repellents are effective and the public should take heed of the tips below:
  • Read the label instructions carefully first;
  • Apply right before entering an area with risk of mosquito bites;
  • Apply on exposed skin and clothing;
  • Use DEET of up to 30 per cent for pregnant women and up to 10 per cent for children*;
  • Apply sunscreen first, then insect repellent; and
  • Re-apply only when needed and follow the instructions.

​* For children who travel to countries or areas where mosquito-borne diseases are endemic or epidemic and where exposure is likely, those aged 2 months or above can use DEET-containing insect repellents with a DEET concentration of up to 30 per cent.

     ​​The public should call 1823 in case of mosquito problems and may visit the following pages for more information: the DF page of the CHP and the Travel Health Service, the latest Travel Health Newstips for using insect repellents, and the CHP Facebook Page and YouTube Channel.

Ends/Thursday, December 7, 2023
Issued at HKT 21:16