FEHD releases fifth batch of gravidtrap indexes for Aedes albopictus in August

The FEHD has so far announced five batches of gravidtrap indexes for Aedes albopictus in August, covering 31 survey areas. Among these 31 survey areas, 18 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. Ten other areas recorded a slight increase, but the indexes were lower than 10 per cent. 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#Issued at HKT 17:00