LCQ18: Prevention of mosquito-borne diseases
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Question:
The Centre for Health Protection of the Department of Health (DH) has pointed out that, with the increase in temperature and rainfall in summer, the risk of transmission of mosquito-borne diseases (including chikungunya fever (CF) and dengue fever (DF)) increases. It has been reported that outbreaks of CF have occurred in neighbouring areas of Hong Kong, and local outbreaks of DF were seen in past summers. In this connection, will the Government inform this Council:
(1) of the respective numbers of CF and DF cases recorded in Hong Kong in each of the past five years, and among them, the respective numbers of local and imported cases;
(2) of the number of fever cases detected in the health screening work at various boundary control points (BCPs) in the past three months, and among them, the number of cases eventually confirmed to be mosquito-borne diseases;
(3) how DH will strengthen the health screening work for travellers from areas with high risk of mosquito-borne diseases at various BCPs (including all land BCPs and the airport), for example, whether it will consider conducting rapid tests on travellers showing relevant symptoms and passengers on relevant flights, so as to shorten the time required for confirming mosquito-borne diseases;
(4) how the Food and Environmental Hygiene Department and relevant government departments will step up mosquito control efforts in areas with serious mosquito infestation in Hong Kong, and of the details of such mosquito control work so far this year; and
(5) whether the Government will consider introducing new technologies to enhance the effectiveness of mosquito control work?
Reply:
President,
The Centre for Health Protection (CHP) of the Department of Health (DH) has all along been closely monitoring the global situation of mosquito-borne diseases (including dengue fever (DF) and chikungunya fever (CF) mentioned in the question).
Regarding DF, according to the World Health Organization (WHO), the global incidence of DF has markedly increased over the past two decades, posing a substantial public health challenge. DF patients may have high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen lymph nodes and rash. Some infected people may not develop apparent symptoms, while some may only have mild and non-specific symptoms such as fever and rash. The symptoms of first infection are usually mild. Once recovered, lifelong immunity to that serotype of dengue virus will develop. However, cross-immunity to the other three serotypes after recovery is only partial and temporary. Subsequent infections with other serotypes of dengue virus are more likely to result in severe dengue or even progress to death. In 2023, over 6.5 million cases (including more than 7 300 deaths) were reported in over 80 countries/regions. In 2024, over 14 million cases were recorded, which was a record high.
Regarding CF, according to the WHO, CF cases with local transmission have been recorded in more than 110 countries/regions. Patient may suffer from fever and debilitating joint pain. Severe symptoms and deaths from CF are rare and usually related to other coexisting health problems. Most patients recover fully. From January to July this year, more than 240 000 cases were recorded in 16 countries/regions worldwide, including about 90 deaths. In Asia, India and Indonesia recorded more than 32 000 and 17 000 cases respectively in 2025. Other regions that have recorded CF cases include the Mainland, Bangladesh and Sri Lanka, etc. Guangdong Province (especially Foshan City) has recorded more than 10 000 CF cases since July. The illness was generally mild with no deaths reported. The situation was under control since late August, with only sporadic new cases reported each day. Since July, Hong Kong has also recorded sporadic imported cases from different places around the world where there are confirmed cases, indicating that the risk of an outbreak still exists and the public should stay vigilant.
In addition, Japanese encephalitis (JE) is also a mosquito-borne disease and imported cases have also been recorded in Hong Kong. JE occurs mainly in the rural and agricultural areas of Asia and the Western Pacific Region, especially during hot seasons. Most infections occur without apparent symptoms or with mild symptoms such as fever and headache. However, approximately one in every 250 infections is associated with severe illness characterised by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis, and even death.
Aedes albopictus is the vector for both DF and CF; and the Culex species is the principal vector for JE. For the prevention and control of mosquito-borne diseases, mosquito prevention and control work is of paramount importance. Under the interdepartmental Pest Control Steering Committee (PCSC) convened by the Environment and Ecology Bureau (EEB), relevant government bureaux and departments have implemented various prevention and control measures against mosquito-borne diseases.
In response to the Hon Leung Man-kwong's enquiry, our reply in consultation with the EEB and the DH is as follows:
(1) On DF, Hong Kong recorded two to 161 DF cases annually in the past five years (2020 to 2024), with the majority being imported cases. As of September 4, 2025, Hong Kong has recorded 44 DF cases this year, all being imported cases from India, Indonesia, the Philippines, Thailand, Malaysia, Cambodia, Fiji, Sri Lanka, Bangladesh and Singapore. Detailed figures are in the following table.
| Year | Local cases | Imported cases | Total |
| 2020 | 1 | 21 | 22 |
| 2021 | 0 | 2 | 2 |
| 2022 | 0 | 26 | 26 |
| 2023 | 0 | 62 | 62 |
| 2024 | 5 | 156 | 161 |
| 2025 | 0 | 44 | 44 |
On CF, no local case has been recorded in Hong Kong in the past five years (2020 to 2024). As of September 4, 2025, Hong Kong has recorded 13 CF cases this year, all being imported cases, with seven cases from the Mainland China (Foshan City of Guangdong Province), four cases from Bangladesh, one case from Indonesia and one case from Sri Lanka.
On JE, Hong Kong has not recorded any cases in the past five years (2020 to 2024). As of September 4, 2025, Hong Kong has recorded one imported case from the Philippines in 2025.
(2) From June to August 2025, the DH detected 991 fever cases among inbound travellers during health screenings at the boundary control points (BCPs). None of these cases was confirmed to have mosquito-borne diseases.
(3) The DH implements health screening measures for inbound travellers at all cross-border ports (including the Hong Kong International Airport and land and sea ports connecting to the Guangdong Province). These measures involve temperature checks and, when necessary, further health assessments for individuals with fever or those reporting symptoms (e.g. those self-reporting discomfort) according to the established mechanism. A health assessment form is used to gather information on symptoms, travel history and contact history, which enables appropriate referrals and follow-up actions.
Since reporting of a CF outbreak by the heath authorities of the Guangdong Province in mid-July this year, the Port Health Division (PHD) of the DH has maintained close liaison with Shenzhen Customs and enhanced mutual notification mechanisms to ensure smooth implementation of port control measures. If travellers with fever or related symptoms are suspected of having CF after assessment by PHD staff, they will be immediately referred to public hospitals in Hong Kong for follow-up. No suspected CF cases have been found at the BCPs so far.
The PHD of the DH continues to maintain close communication with relevant stakeholders (e.g. airlines and tourism industry) to update disease information and health advice promptly. PHD staff will also closely monitor environmental hygiene at all BCPs, strengthen inspections, fully implement mosquito prevention and control work at BCPs, and ensure good environmental hygiene and vector control measures are in place.
Mosquito-borne diseases (including DF, CF and JE) have a long incubation period, potentially up to about two weeks. Port health measures alone are therefore insufficient to detect infected cases at the place of entry. At the same time, for DF and CF, the viral load in an infected person's blood is the highest in the first few days after symptom onset. Therefore, the diagnosis during the early stage of the diseases is accurate only through viral nucleic acid testing of the patient's blood. DF and CF nucleic acid testing products must be used by professional personnel in laboratory settings. Currently, there are no rapid nucleic acid test products on the market that have been certified by international health authorities for self-testing outside laboratory settings. As for the existing rapid test kits for CF on the market, they target antibodies in patient's body. Since the body typically takes about a week to produce antibodies against the chikungunya virus, such rapid tests are not suitable for use in the early stage of the diseases and may result in false negatives, thereby unable to shorten the time for diagnosis.
(4) All departments concerned have been actively implementing anti-mosquito measures. The EEB held interdepartmental PCSC meetings in March and July this year respectively to review the latest situation of the mosquito problem and the mosquito prevention and control work carried out by various departments. Under the inter-departmental coordination mechanism, the Food and Environmental Hygiene Department (FEHD) and relevant departments have carried out a series of mosquito prevention and control work, as well as strengthened the related measures in response to CF cases reported in neighbouring regions. The details of the enhanced measures are as follows:
Vector surveillance
The FEHD continues to place gravidtraps in different areas across Hong Kong for monitoring the infestation of Aedes albopictus mosquitoes, which can transmit DF and CF. The FEHD publishes the Area Gravidtrap Indices (AGI) on its departmental webpage and the Government's Geospatial Information Hub platform on a regular basis, so that government departments and stakeholders can adopt targeted mosquito control measures with respect to the surveillance results. To further step up mosquito prevention and control, since August this year, the FEHD has extended its strengthened mosquito control work, which was originally initiated when the AGI of an area has reached 20 per cent, to also cover areas with AGI between 10 per cent and 20 per cent. The FEHD will conduct detailed risk assessment for the areas concerned to identify locations with more severe mosquito infestation, so as to carry out intensive and targeted mosquito control work jointly with other departments and stakeholders. The FEHD will also notify the nearby housing estates, advising their property management companies and residents to stay vigilant and join hands in taking anti-mosquito measures.
Minimising mosquito breeding grounds and eliminating mosquitoes
With the primary focus on environmental control, the FEHD's mosquito prevention and control work focuses on minimising mosquito breeding grounds. Biological or chemical methods, including applying larvicides and conducting fogging operations, are carried out to eliminate adult mosquitoes so as to control their population. From January to August 2025, the FEHD conducted over 22 000 fogging operations across the territory to eliminate adult mosquitoes.
In addition, the FEHD has stepped up inspections of high-risk locations such as construction sites and works sites. From January to August 2025, the FEHD instituted a total of 103 prosecutions, including 95 cases involving construction sites and eight cases involving other premises. Since August 2025, the FEHD has issued over 200 statutory notices to construction sites and works sites, instructing them to clear stagnant water.
Inter-departmental and cross-sectoral collaboration
The FEHD has convened special meetings of the inter-departmental task forces on anti-mosquito work across districts to coordinate with relevant departments and stakeholders in implementing targeted and sustained mosquito prevention and control measures, including actively implementing anti-mosquito measures in their respective premises and venues.
The FEHD issued letters to the property management sector and the pest control sector, calling on them to promote and implement anti-mosquito measures among the residents or work units of the housing estates under their management. Moreover, the FEHD, the Property Management Services Authority and the CHP jointly held a large-scale seminar providing information on the prevention and control measures against CF for about 3 000 practitioners of the property management sector.
The FEHD has also collaborated with the Development Bureau to issue the "Guidelines on Mosquito Prevention in Construction Sites" to over 200 construction sites and relevant personnel through the Construction Industry Council, reminding the practitioners to take appropriate anti-mosquito and personal protective measures. In addition, prior to the start of the new school year, the FEHD issued the "Guidelines on Mosquito Prevention in Schools" through the Education Bureau to over 2 000 schools across the territory, including kindergartens, primary schools and secondary schools, so as to facilitate preventing the risk of mosquito-borne disease transmission in schools.
(5) The FEHD has been applying technologies to enhance the effectiveness of mosquito control. For example, the FEHD has adopted over 2 000 new mosquito trapping devices, using adult mosquitoes as carriers to carry growth regulators to different water bodies so that larvae in the water bodies cannot develop into adult mosquitoes, to suppress the density of adult mosquitoes. Moreover, the FEHD is working with the Electrical and Mechanical Services Department to conduct on-site trials on robot dogs carrying out fogging operations at inaccessible places such as shrubby areas to enhance the anti-mosquito effectiveness.
The FEHD will closely monitor the latest information from the WHO and other places concerning mosquito control measures. The FEHD will also study the feasibility of introducing the new technologies and products to Hong Kong. Should any suitable new technologies and products be identified, the FEHD will actively consider their introduction and application.
Ends/Wednesday, September 10, 2025
Issued at HKT 19:06
Issued at HKT 19:06
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