Public urged to heighten vigilance against mosquito-borne diseases (with photo)

     In light of the increasing threat of dengue fever (DF) globally, the Department of Health (DH) and the Food and Environmental Hygiene Department (FEHD) today (July 18) reminded members of the public to stay vigilant against mosquito-borne diseases, enhance anti-mosquito awareness, implement mosquito control and personal protective measures both locally and during travel.

     According to the World Health Organization, the global incidence of DF has increased significantly over the past year. Since 2024, more than 10 million cases have been recorded in the Americas, which is a record high. A total of 37 cases have been recorded in Hong Kong as of yesterday (July 17), of which 34 are imported cases and three are local cases. Most of the imported cases have visited some tourist spots in Southeast Asia, including Indonesia, Malaysia, and Thailand, during the incubation period. The three local cases include one recorded in April with a patient living in Siu Sai Wan and two recorded in June with both patients living in Tin Shui Wai. The Centre for Health Protection (CHP) of the DH has conducted active case finding and medical surveillance for the local cases. For the cases in Tin Shui Wai, as of yesterday (July 17), more than 5 200 residents in 2 000 households of the housing estate where the patients residing were reached. So far, no new cases have been found. The prevention and control measures implemented by the CHP in Tin Shui Wai are continuing.

     In view of the two local DF cases that occurred in Tin Shui Wai, the FEHD has conducted vector mosquito investigations and targeted mosquito control operations. The FEHD has intensified mosquito prevention and control work in the residences, workplaces and locations visited by the patients during the incubation period and after illness onset. These efforts include:

•  conducting fogging operations in the scrubby areas within a 250-metre radius of the related locations to eradicate adult mosquitoes;
•  carrying out weekly inspections of the above locations, removing stagnant water, applying insecticide and disposing of abandoned water containers to prevent mosquito breeding; and
•  stepping up publicity and education work, including organising health talks, deploying the Mobile Education Centre and distributing leaflets.
 
     The latest territory-wide Aedes albopictus mosquito surveillance shows that Aedes albopictus is widely distributed in Hong Kong. The hot and rainy weather this summer is conducive to the breeding of mosquito vectors. In addition, more people travelling abroad during the summer may increase the chance of acquiring DF infection, leading to an increase in imported cases. In this connection, the CHP cannot exclude the possibility of a further increase in the risk of local DF transmission. To prevent the further spread of DF and its evolution into an endemic disease, the public should co-operate with the Government to implement effective mosquito prevention and control measures at this critical juncture.

     DF is clinically characterised by high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen lymph nodes and rash. The CHP appeals to the public, in particular residents in Tin Shui Wai, to pay special attention to anti-mosquito measures. If feeling unwell, one should seek medical advice as soon as possible and call the CHP hotline (2125 2374) if in doubt.

     In order to assess the knowledge, attitude and practice of the general public towards mosquito-borne diseases and its prevention, the CHP commissioned a survey between January and February of 2024, in which 2 002 members of the public aged 18 or above were successfully interviewed.

     In the survey, it was found that the respondents had good awareness of mosquito-borne diseases, with 92.7 per cent of the respondents correctly identifying DF as a mosquito-borne disease, while the figures for Japanese encephalitis and malaria were 83.0 per cent and 68.6 per cent respectively. However, their awareness of the transmission and complications of mosquito-borne diseases was relatively low. Only less than half of them (44.9 per cent) acknowledged that a second infection of DF virus with different serotypes could lead to severe disease, and only about 30 per cent of the respondents could correctly point out that asymptomatic individuals infected with dengue fever virus can transmit the virus to mosquitoes.

     The survey also found that the insect repellent knowledge of the respondents was not sufficient. 77.6 per cent of the respondents did not know the effective ingredients of insect repellents, and 98.8 per cent of them were uncertain about the recommended diethyltoluamide (DEET) concentration. Although around 65 per cent of the respondents agreed that insect repellents could protect them from mosquito-borne diseases, the proportion of respondents who could use insect repellents properly was relatively low. 70.0 per cent of them did not check the ingredients when purchasing insect repellents, while 69.7 per cent never applied insect repellents for 14 days when returning to Hong Kong from affected areas of DF to prevent mosquito bites.

     A spokesman for the CHP reminded travellers going to DF affected countries or areas to take extra precautionary measures to prevent mosquito bites. Travellers who return from affected areas should apply insect repellent for 14 days after arrival to prevent mosquito bites. If feeling unwell such as having a fever, the person should seek medical advice promptly and provide travel details to the doctor.
 
     Moreover, the spokesman stressed that the public should read the label instructions carefully when purchasing insect repellents and could choose insect repellents containing DEET. The public should take heed of the tips below when applying DEET-containing insect repellents:
 

• 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
• Reapply only when needed and follow the instructions.

* For children who travel to countries or areas where mosquito-borne diseases are prevalent and where mosquito bite is likely, those aged 2 months or above can use insect repellents with a DEET concentration of up to 30 per cent. They also should apply insect repellent appropriately for 14 days upon arrival in Hong Kong to prevent mosquito bites.

     Furthermore, 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;
• 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 according to product label and uncovered areas of the body when doing outdoor activities.

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