The Food and Environmental Hygiene Department (FEHD) today (September 9) announced that the monthly gravidtrap index (MGI) for Aedes albopictus mosquitoes in August was 5.3 per cent, lower than the 8.1 per cent in July. This reflects the continued efforts by relevant government departments to intensify mosquito prevention and elimination operations, resulting in the improvement of the overall mosquito infestation situation this month. In addition, the FEHD has strengthened the dissemination of information on the gravidtrap index for Aedes albopictus mosquitoes so that more citizens can quickly grasp the mosquito infestation situation. The department will continue its mosquito control work to further reduce the risk of transmission of chikungunya fever (CF) and dengue fever (DF).

     In August, all 64 survey areas recorded an area gravidtrap index (AGI) lower than the alert level of 20 per cent. The decreases in the MGI and the number of survey areas with an AGI exceeding the alert level in August are attributable to the continuous and intensified mosquito prevention and elimination operations by various government departments and stakeholders, and may also have been affected by factors such as weather. The monthly rainfall was 939.2 millimetres in August, showing a significant increase from the 601.7mm in July and 237.3mm in June. Overall, the MGI for Aedes albopictus mosquitoes in August was 5.3 per cent, at Level 2 (indicating the distribution of Aedes albopictus mosquitoes in the survey areas was fairly extensive). Relevant departments and stakeholders will persistently intensify mosquito prevention and elimination operations.

     Moreover, the monthly density index for Aedes albopictus in August was 1.1, which represented that an average of 1.1 Aedes albopictus adults were found in the Aedes-positive gravidtraps, indicating that the number of adult Aedes albopictus was not abundant in the survey areas.

     The FEHD currently makes regular announcements on gravidtrap indexes for Aedes albopictus on its webpage. To allow more citizens to quickly grasp the mosquito infestation situation, the FEHD has strengthened information dissemination by promptly announcing the latest gravidtrap indexes through press releases and social media.

     In addition, to further reduce the risk of transmission of CF, the FEHD has extended the intensified mosquito control work, which was originally activated when the AGI reaches 20 per cent, to cover areas with the AGI falling between 10 and 20 per cent. Specifically, the FEHD will conduct detailed risk assessments in the areas concerned to identify locations with higher mosquito infestation risks, and in collaboration with relevant departments and stakeholders, conduct intensive and targeted mosquito control work. The FEHD will also notify the nearby housing estates, advising property management agents and residents to stay vigilant and join hands in taking mosquito prevention and elimination measures.

     To reduce the risk of transmission of CF and DF, the FEHD continues to step up mosquito prevention and control measures across all districts, and to conduct vector investigations and targeted mosquito control operations within a 250 metre radius of the residence of patients and the places patients had visited during the infectious period, including removing mosquito breeding grounds, applying larvicides to stagnant water that cannot be cleared, and carrying out ultra-low volume fogging operations in adult mosquito habitats such as densely wooded areas, dark and secluded places, and abandoned structures to eliminate adult mosquitoes.

     The FEHD continues to conduct its three-phase Anti-mosquito Campaign this year. The third phase of the territory-wide campaign was launched on August 4 and will run until October 24. During the period, the district offices of the FEHD will target areas that have drawn particular concern, such as public markets, cooked food centres and hawker bazaars, single-block buildings, streets and back lanes, common parts of buildings, village houses, construction sites, vacant sites and road works sites, to remove accumulated water and carry out mosquito prevention and control work. To further enhance the effectiveness of mosquito control, the FEHD and relevant government departments have carried out phase two of the All-out Anti-mosquito Operations from May 7. In addition to the work of phase one, including eliminating potential mosquito breeding places, the FEHD called on property management entities to arrange for necessary repairs to their premises to minimise mosquito breeding places and commence adult mosquito control measures by means of regular ultra-low volume fogging operations.

     The FEHD appeals to members of the public to continue to stay alert and work together to carry out mosquito prevention and control measures early, including inspecting their homes and surroundings to remove potential breeding grounds, changing water in vases and scrubbing their inner surfaces, removing water in saucers under potted plants at least once a week, and properly disposing of containers such as soft drink cans and lunch boxes. 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 DF and CF. DF is commonly found in tropical and subtropical regions of the world, and has become endemic in many countries in Southeast Asia. In 2024, the World Health Organization (WHO) recorded over 14 million cases, which was a record number. Additionally, according to the WHO, CF cases have been recorded in more than 110 countries/regions. Many countries worldwide experienced CF outbreaks this year, and as of July, over 240 000 cases had been reported in 16 countries/regions worldwide. The DF and CF activities in neighbouring areas have remained high. Members of the public should stay vigilant and continue to carry out effective mosquito prevention and control measures.

Ends/Tuesday, September 9, 2025
Issued at HKT 19:50

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