Source: Hong Kong Government special administrative region – 4
The Food and Environmental Hygiene Department (FEHD) today (August 20) released the sixth batch of gravidtrap indexes and density indexes for Aedes albopictus in August, covering 11 survey areas, as follows:
| District |
Survey Area |
August 2025 |
| First Phase Gravidtrap Index |
First Phase Density Index |
| Central/ Western |
Sai Wan |
5.5% |
1.0 |
| Southern |
Aberdeen and Ap Lei Chau |
3.8% |
1.0 |
| Wanchai |
Tin Hau |
1.8% |
1.0 |
| Kowloon City |
Lok Fu West |
5.1% |
1.0 |
| Kai Tak North |
17.5% |
1.4 |
| Sha Tin |
Sha Tin Town Centre and Fo Tan |
2.0% |
1.0 |
| Yuen Long |
Ki Lun Shan |
0.0% |
N/A |
| Sung Shan |
4.2% |
1.0 |
| Tsuen Wan |
Ma Wan |
20.0% |
1.4 |
| District |
Survey Area |
August 2025 |
| Area Gravidtrap Index |
Area Density Index |
| Eastern |
Shau Kei Wan and Sai Wan Ho |
7.0% |
1.3 |
| Kwun Tong |
Kwun Tong Central |
2.3% |
1.0 |
Among the sixth batch of First Phase Gravidtrap Indexes covering nine survey areas and Area Gravidtrap Indexes covering two survey areas in August, all were below 10 per cent, except the First Phase Gravidtrap Indexes for Kai Tak North in Kowloon City and Ma Wan in Tsuen Wan.
The FEHD has so far announced six batches of gravidtrap indexes for Aedes albopictus in August, covering 40 survey areas. Among these 40 survey areas, 24 recorded a decrease or remained unchanged in the individual gravidtrap index as compared with the Area Gravidtrap Index last month, i.e. July 2025, representing the areas’ mosquito infestation improved or maintained at a low level. Eleven other areas recorded a slight increase, but the indexes were lower than 10 per cent.
Among the sixth batch of indexes released, Kai Tak North in Kowloon City and Ma Wan in Tsuen Wan recorded an index over 10 per cent. In accordance with the mechanism implemented by the FEHD in response to the recent chikungunya fever (CF) situation, the FEHD is collaborating with relevant departments and stakeholders to identify locations with high mosquito infestation and carry out intensive and targeted mosquito control measures. In particular, the gravidtrap data for Kai Tak North showed that the locations with more mosquito problems included public and private housing estates, while the gravidtrap data for Ma Wan showed that the locations with more mosquito problems included parks, beaches, schools, private housing estates and construction sites. The gravidtrap index for Ma Wan survey area dropped from 30.4 per cent in first phase to 24.4 per cent in July, and its First Phase Gravidtrap Index in August further dropped to 20 per cent. The relevant departments and stakeholders are actively following up on the mosquito control work. Additionally, the FEHD will also organise exhibitions, distribute leaflets and posters, and notify the residential estates subscribed to the gravidtrap Rapid Alert System, advising property management agents and residents to stay vigilant and join hands in taking mosquito prevention and elimination measures.
Public participation is crucial to effective control of mosquito problems. The FEHD appeals to members of the public to continue joining hands in strengthening personal mosquito control measures, including:
- tidy up their premises and check for any accumulation of water inside their premises;
- remove all unnecessary water collection and eliminate the sources;
- check household items (those placed in outdoor and open areas in particular), such as refuse containers, vases, air conditioner drip trays, and laundry racks to prevent stagnant water;
- change the water in flower vases and saucers of potted plants at least once every seven days;
- properly cover all containers that hold water to prevent mosquitoes from accessing the water; and
- properly dispose of articles that can contain water, such as empty lunch boxes and cans.
Starting in August this year, following the completion of surveillance of individual survey areas, and once the latest Gravidtrap Index and the Density Index are available, the FEHD will disseminate the relevant information through press releases, its website, and social media. It aims to allow members of the public to quickly grasp the mosquito infestation situation and strengthen mosquito control efforts, thereby reducing the risk of CF transmission.
Following the recommendations from the World Health Organization and taking into account the local situation in Hong Kong, the FEHD sets up gravidtraps in districts where mosquito-borne diseases have been recorded in the past, as well as in densely populated places such as housing estates, hospitals and schools, to monitor the breeding and distribution of Aedes albopictus mosquitoes, which can transmit CF and dengue fever. At present, the FEHD has set up gravidtraps in 64 survey areas of the community. During the two weeks of surveillance, the FEHD will collect the gravidtraps once a week. After the first week of surveillance, the FEHD will immediately examine the glue boards inside the retrieved gravidtraps for the presence of adult Aedine mosquitoes, to compile the Gravidtrap Index (First Phase) and Density Index (First Phase). At the end of the second week of surveillance, the FEHD will instantly check the glue boards for the presence of adult Aedine mosquitoes. Data of the two weeks’ surveillance will be combined to obtain the Area Gravidtrap Index and the Area Density Index. The gravidtrap and density indexes for Aedes albopictus in different survey areas as well as information on mosquito prevention and control measures are available on the department’s webpage (www.fehd.gov.hk/english/pestcontrol/dengue_fever/Dengue_Fever_Gravidtrap_Index_Update.html#).