Source: Hong Kong Government special administrative region – 4
The Food and Environmental Hygiene Department (FEHD) today (May 26) released the fifth batch of gravidtrap indexes for Aedes albopictus in May, which includes First Phase Gravidtrap Indexes covering 16 survey areas and Area Gravidtrap Indexes covering 10 survey areas. In response to the rise in gravidtrap indexes in recent months, the FEHD has stepped up mosquito prevention and control work across all districts in Hong Kong.
The Director of Food and Environmental Hygiene, Mr Donald Ng, visited Tai Wai in Sha Tin District this afternoon to inspect the enhanced mosquito prevention and control work in the area, including using drones to identify potential mosquito breeding grounds, conducting fogging operations by large ultra-low volume fogger to eradicate adult mosquitoes, and installing new mosquito traps. He also visited local schools and public housing estates, together with Legislative Council member Hon Chan Hak-kan and some local District Council members. While the First Phase Gravidtrap Index of Tai Wai in May had reached 46 per cent, the latest Area Gravidtrap Index has significantly dropped to 24.2 per cent following intensive mosquito control work. The FEHD will remain vigilant and continue to work closely with relevant government departments and stakeholders to sustain effective mosquito prevention and control work.
The fifth batch of gravidtrap indexes and density indexes for Aedes albopictus in May, covering 26 survey areas, is as follows:
| District |
Survey Area |
May 2026 |
| First Phase Gravidtrap Index |
First Phase Density Index |
| Central and Western |
Sheung Wan and Sai Ying Pun |
9.1% |
2.2 |
| Wan Chai |
Happy Valley and Tai Hang |
8.8% |
1.0 |
| Kwun Tong |
Kowloon Bay |
22.8% |
1.2 |
| Sham Shui Po |
Cheung Sha Wan |
19.2% |
1.7 |
| Lai Chi Kok |
9.1% |
1.4 |
| Sham Shui Po and Shek Kip Mei |
27.9% |
1.3 |
| Wong Tai Sin |
Ngau Chi Wan and San Po Kong |
3.7% |
1.5 |
| North |
Sheung Shui |
24.2% |
1.3 |
| Sai Kung |
Sai Kung Town |
19.2% |
1.6 |
| Tseung Kwan O East |
24.6% |
1.1 |
| Tseung Kwan O North |
26.2% |
1.5 |
| Tseung Kwan O West |
9.1% |
2.2 |
| Sha Tin |
Ma On Shan |
32.8% |
1.4 |
| Tuen Mun |
So Kwun Wat |
18.2% |
1.3 |
| Yuen Long |
Hung Shui Kiu and Ping Shan |
6.0% |
1.0 |
| Yuen Long Town |
17.2% |
1.2 |
| District |
Survey Area |
May 2026 |
| Area Gravidtrap Index |
Area Density Index |
| Eastern |
Shau Kei Wan and Sai Wan Ho |
17.0% |
1.6 |
| Southern |
Pok Fu Lam |
15.2% |
1.3 |
| Islands |
Tung Chung |
4.0% |
1.3 |
| Kowloon City |
Ho Man Tin |
23.6% |
1.2 |
| Kwun Tong |
Yau Tong and Cha Kwo Ling |
16.2% |
1.7 |
| Wong Tai Sin |
Wong Tai Sin West |
18.1% |
1.7 |
| Sha Tin |
Tai Wai |
24.2% |
1.7 |
| Tai Po |
Tai Po West |
16.4% |
1.0 |
| Tsuen Wan |
Ma Wan and Sham Tseng |
26.2% |
1.7 |
| Tuen Mun |
Tuen Mun South |
15.5% |
1.3 |
With reference to the data from the past few years, the gravidtrap indexes start to rise from April or May every year. The indexes are higher from April to June. The actual timing and extent of the rise are affected by factors like weather conditions and rainfall. The average temperature and rainfall recorded in April this year were higher than those in the same period last year, creating favourable conditions for mosquito growth and breeding. As a result, the rise in gravidtrap indexes occurred earlier this year. With the increase in rainfall in May, the gravidtrap indexes are expected to rise further. The overall trend of gravidtrap indexes this year are similar to those of previous years.
In response to the rise of gravidtrap indexes in recent months, the FEHD has stepped up mosquito prevention and control work across all districts in Hong Kong, including inspecting construction sites, parks, public and private housing estates, and locations with higher mosquito infestations. Over the past two weeks, the FEHD has initiated 15 prosecutions against the management companies or responsible persons-in-charge of these venues following the discovery of mosquito breeding, and issued 42 statutory notices requiring the clearance of stagnant water or stagnant water containers. Furthermore, for survey areas which recorded indexes exceeding 10 per cent, in accordance with the mechanism implemented by the FEHD in response to the chikungunya fever (CF) situation (i.e. strengthening mosquito control work in areas with a gravidtrap index between 10 per cent and 20 per cent, instead of 20 per cent or above under the original mechanism), the FEHD is collaborating with relevant departments and stakeholders to identify locations with high mosquito infestations and carry out intensive and targeted mosquito control measures. The FEHD, the relevant departments and stakeholders will also organise exhibitions, distribute leaflets and posters, and notify residential estates that have subscribed to the gravidtrap Rapid Alert System, advising property management agents and residents to stay vigilant and work together in taking mosquito prevention and elimination measures.
Public participation is crucial to the effective control of mosquito problems. The FEHD appeals to members of the public to continue to work together in strengthening personal mosquito control measures, including:
- tidy up their premises and check for any accumulation of water inside the premises;
- remove all unnecessary water collections 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 water in flower vases and scrub their inner surfaces thoroughly, and remove water in saucers under potted plants at least once a week;
- properly cover all containers that hold water to prevent mosquitoes from accessing the water;
- properly dispose of articles that can contain water, such as disposable meal boxes and empty cans; and
- scrub drains and surface sewers with alkaline detergent at least once a week to remove any mosquito eggs.
Starting in August 2025, following the completion of the surveillance of individual survey areas, and once the latest gravidtrap index and the density index are available, the FEHD has been disseminating 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 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 62 survey areas of the community, with a surveillance period of two weeks. During the surveillance period, 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 from the two weeks of 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#).