FEHD releases fourth batch of gravidtrap indexes for Aedes albopictus in May
Source: Hong Kong Government special administrative region
FEHD releases fourth batch of gravidtrap indexes for Aedes albopictus in May
District
District The fourth batch of gravidtrap indexes for Aedes albopictus in May includes First Phase Gravidtrap Indexes covering six survey areas and Area Gravidtrap Indexes covering six survey areas. Among which, six survey areas recorded gravidtrap indexes above 10 per cent, while Aberdeen and Ap Lei Chau in Southern District recorded a gravidtrap index above 20 per cent. Meanwhile, the gravidtrap indexes of six survey areas, namely Kennedy Town and Shek Tong Tsui in Central and Western District; North Point and Quarry Bay in Eastern District; Shau Kei Wan and Sai Wan Ho in Eastern District; Aberdeen and Ap Lei Chau in Southern District; Tai Po East in Tai Po District; and Tuen Mun South in Tuen Mun District, have recorded a decrease as compared to the indexes recorded in the last survey period, reflecting the progress of relevant mosquito control work.
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 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. 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#Issued at HKT 21:17