Update on dengue fever and chikungunya fever

     The Centre for Health Protection (CHP) of the Department of Health today (July 19) reported the latest number of cases of dengue fever (DF) and chikungunya fever (CF), and again urged the public to maintain strict environmental hygiene, mosquito control and personal protective measures both locally and during travel.
 
A. Dengue fever
 
     From July 12 to 18, the CHP recorded seven imported DF cases. The patients had been to Cambodia (two cases), Malaysia (two epidemiologically linked cases), Indonesia (one case), Nepal (one case) and multiple countries (one case, who had been to Cambodia and Laos) during the incubation period.
 
     As of yesterday (July 18), 84 cases had been recorded this year, all of which were imported. The cases were mainly imported from Malaysia (17), Thailand (15) and Indonesia (13).
     
     The CHP has been closely monitoring the latest DF situation in neighbouring and overseas areas. DF is endemic in many tropical and subtropical areas of the world. Detailed information on the latest DF situation in Hong Kong as well as neighbouring and overseas countries and areas this year has been uploaded to the CHP's website (www.chp.gov.hk/files/pdf/df_imported_cases_and_overseas_figures_eng.pdf).
 
     According to the ovitrap data from the Food and Environmental Hygiene Department, the monthly ovitrap index for Aedes albopictus rose from 11 per cent in May to 16 per cent in June, indicating that mosquito infestation was slightly more extensive in the areas surveyed. Members of the public, especially residents in areas with extensive mosquito infestation, should stay vigilant and carry out effective mosquito prevention and control measures.
 
     ​"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.
 
B. Chikungunya fever
 
​     From July 12 to 18, the CHP confirmed one CF case. The patient had been to Thailand (epidemiologically linked to the cluster of three cases recorded last week) during the incubation period. Apart from this cluster of four CF cases who had travelled to Thailand together during the incubation period, no other confirmed CF cases were recorded in Hong Kong in 2019.
 
     CF is a mosquito-borne disease caused by the chikungunya virus. It is clinically characterised by fever frequently accompanied by joint pain. Other common signs and symptoms include muscle pain, headache, nausea, fatigue and rash. Joint pain is often very debilitating, but usually lasts for a few days or may be prolonged for weeks. Most patients recover fully, but in some cases joint pain may persist for several months, or even years.
 
     Chikungunya virus is transmitted to humans by mosquito bites. Although one vector, Aedes aegypti, is not found in Hong Kong, the other vector, Aedes albopictus, is widely distributed locally. These mosquitoes can be found biting throughout daylight hours, though there may be peaks of activity in the early morning and late afternoon.
 
     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 CF page of the CHP, the latest Travel Health News, tips for using insect repellents, and the CHP Facebook Page and YouTube Channel.