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, inspected the enhanced mosquito prevention and control work in Tai Wai in Sha Tin District this afternoon, 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 schools and public housing estates in the area.  Legislative Council member Hon Chan Hak-kan and some local District Council members joined the visit.  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#).

Ends/Tuesday, May 26, 2026
Issued at HKT 22:41

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