Monthly gravidtrap index for Aedes albopictus in December 2021 drops further


     The Food and Environmental Hygiene Department (FEHD) today (January 21) announced that the monthly gravidtrap index for Aedes albopictus in December 2021 further dropped to 0.1 per cent, lower than that of 2.2 per cent in November last year. The index in December remained at Level 1 at its lowest, indicating that distribution of Aedes albopictus in the areas surveyed was not extensive.

     Among the 64 survey areas, no area recorded a gravidtrap index exceeding the alert level of 20 per cent. Moreover, the monthly density index for Aedes albopictus in December last year was 1, which represented that an average of one Aedes albopictus adult was found in the Aedes-positive gravidtraps, indicating that the number of adult Aedes albopictus was not high in the areas surveyed. The gravidtrap and density indices for Aedes albopictus in different areas and information on mosquito prevention and control measures are available on the department's website at

     Despite the index drops further and remains at a low level, the breeding and activity of mosquitoes will continue in winter. It is hoped that the community would continue to work together with the Government in mosquito control and prevention. The FEHD launched its territory-wide year-end clean-up campaign on January 8, during which mosquito prevention and control work will be enhanced, including carrying out inspections, removing stagnant water, applying insecticide and disposing of abandoned water containers weekly to prevent mosquito breeding, and trimming of grass to discourage resting of adult mosquitoes on the site. At the same time, the FEHD and relevant government departments will continue the above mosquito prevention and control work in areas under their purview and strengthen publicity and education work.

     A spokesman for the FEHD said, "Effective mosquito control requires the sustained effort of all parties concerned. The community must work together with the Government to carry out effective mosquito control measures."

     The FEHD appeals to members of the public to continue to carry out mosquito prevention and control measures including inspecting their homes and surroundings to remove potential breeding grounds, changing the water in vases and scrubbing the inner surfaces, removing the water in saucers under potted plants at least once a week, properly disposing of containers such as soft drink cans and lunch boxes, and drilling large holes in unused tyres. The FEHD also advises members of the public and estate management bodies to keep drains free of blockage and level all defective ground surfaces to prevent the accumulation of water. They should also scrub all drains and surface sewers with an alkaline detergent at least once a week to remove any mosquito eggs.

     Aedes albopictus is a kind of mosquito that can transmit dengue fever (DF) as well as Zika virus infection. DF is commonly found in tropical and subtropical regions of the world, and has become endemic in many countries in Southeast Asia. The dengue activity in neighbouring areas has remained high and Hong Kong has recorded two imported DF cases so far since last year.

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