FEHD releases sixth batch of gravidtrap indexes for Aedes albopictus in April
The Food and Environmental Hygiene Department (FEHD) today (May 5) released the sixth batch of gravidtrap indexes and density indexes for Aedes albopictus in April, covering 15 survey areas, as follows:
Among the sixth batch of First Phase Gravidtrap Indexes covering one survey area and Area Gravidtrap Indexes covering 14 survey areas in April, all were below 10 per cent, except for the Area Gravidtrap Indexes of Ngau Chi Wan and San Po Kong in Wong Tai Sin District, and So Kwun Wat in Tuen Mun District.
With reference to the data from the past few years, the gravidtrap indexes start to rise from April or May every year. The actual timing of the increaseandits extent are affected by factors like weather and rainfall. The average temperature and rainfall in April this year were higher than those of the same period last year, creating favourable conditions for mosquito growth and breeding and thus leading to the earlier rise of gravidtrap indexes this year, but the overall trend and extent of the increase are similar to those of previous years. In response to the rise of gravidtrap indexes, the FEHD, together with relevant departments and stakeholders, has implemented rapid response measures and deployed targeted actions.
For Ngau Chi Wan and San Po Kong in Wong Tai Sin District, and So Kwun Wat in Tuen Mun District, 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. In particular, the gravidtrap data for Ngau Chi Wan and San Po Kong showed that areas with more mosquito problems included parks, schools and public housing estates, while the gravidtrap data for So Kwun Wat showed that areas with more mosquito problems included parks and private housing estates.
In response to the high-risk areas identified in the said survey areas, the FEHD has issued a statutory notice to a relevant construction site contractor following the discovery of stagnant water at a construction site in So Kwun Wat in Tuen Mun District, requiring the clearance of such item within a specified timeframe. The FEHD and the relevant departments are following up on the mosquito control work, and 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. In addition, the FEHD will strengthen the monitoring of the gravidtrap index in the areas to review the effectiveness of the mosquito control work.
The FEHD has so far released six batches of gravidtrap indexes for Aedes albopictus in April 2026, covering 62 survey areas. Among these 62 survey areas, one recorded a decrease or remained unchanged as compared to the Area Gravidtrap Index last month (i.e. March 2026), representing that the area's mosquito infestation improved or maintained a low level. Fifty-one other areas recorded a slight increase, but the indexes were lower than 10 per cent.
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:
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#).
FEHD releases sixth batch of gravidtrap indexes for Aedes albopictus in April Source: HKSAR Government Press Releases
FEHD releases sixth batch of gravidtrap indexes for Aedes albopictus in April Source: HKSAR Government Press Releases
FEHD releases sixth batch of gravidtrap indexes for Aedes albopictus in April Source: HKSAR Government Press Releases
