Flu Activity Declines in Hong Kong; Public Urged to Stay Vigilant and Get Vaccinated

Summer influenza season nears its end and winter influenza season yet to begin Public must remain vigilant despite influenza activity declines

The Centre for Health Protection (CHP) of the Department of Health today (January 3) reminded the public that seasonal influenza activity has gradually declined over the past two weeks to near baseline levels. This indicated that the summer influenza season, which began in early September last year, might conclude within the next one to two weeks. Nevertheless, the CHP urged the public to remain vigilant and maintain good personal and environmental hygiene at all times. Those who have not yet received seasonal influenza vaccination (SIV), particularly high-risk groups such as pregnant women, the elderly, children and those with underlying illnesses, should receive SIV promptly to reduce the risk of severe illness and death from infection.

Latest surveillance data

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"Hong Kong entered the summer influenza season in early September last year. The seasonal influenza activity peaked in mid-to-late October last year and has since been gradually declining. The latest surveillance data shows that the percentage of respiratory specimens tested positive for seasonal influenza viruses last week (December 21 to 27, 2025) decreased to 4.97 per cent from 7.81 per cent and 6.17 per cent in the previous two weeks (the baseline level is 4.94 per cent). The influenza admission rate in public hospitals was 0.28 cases per 10 000 population (lower than the 0.49 and 0.37 cases per 10 000 population recorded in the previous two weeks, with the baseline level of 0.27 cases per 10 000 population). Regarding outbreaks of influenza-like illness in schools, the number rose sharply from 15 outbreaks in the first week of the new school year last September to 170 outbreaks in mid-October, before gradually declining to 43 outbreaks in mid-November. After a slight rebound to 71 outbreaks in early December last year, the number has steadily decreased over the past few weeks, falling from over 30 outbreaks per week to just four outbreaks last week. The CHP will continue to closely monitor local surveillance data. Should relevant indicators persistently fall below the baseline levels, the CHP will assess next week whether this summer influenza season has concluded," the Controller of the CHP, Dr Edwin Tsui, said.

The predominant virus circulating during this seasonal influenza season is influenza A (H3) virus strain. As in the past, severe or death cases associated with seasonal influenza primarily affect the elderly and children. As of January 1, this summer influenza season has recorded 25 severe paediatric influenza cases, including three fatal cases. The affected children aged between six months to 17 years old. Among them, 20 cases (80 per cent) had not received SIV (including one case who received the 2025/26 SIV only four days before onset of illness. As it generally takes two weeks for the body to develop sufficient protection after vaccination, the case was not protected by the vaccine. Therefore, it is not counted as vaccinated). During the same period, 502 severe influenza cases were recorded among adults, including 339 deaths. Among adult fatalities with available clinical data, over 80 per cent had underlying illnesses.

"Although the summer influenza season shows signs of ending and the winter influenza season has not yet begun, influenza activity may rise again as the weather gradually turns colder in the first quarter of this year. It cannot be ruled out that the circulating virus strains may change. Therefore, I once again urge all individuals aged six months or older, except those with known contraindications, who have not yet received SIV to act promptly. Although there are some antigenic differences between the currently circulating influenza A (H3) virus strain and the virus strain contained in the vaccine, SIV can still offer protection against the variant strain of subclade K, as well as the influenza A (H1) and influenza B strains included in the vaccine. Those who contracted influenza during the summer influenza season should still receive the 2025/26 SIV, if they have not yet done so, to guard against other circulating virus strains that may emerge during the forthcoming winter influenza season," Dr Tsui added.

2025/26 SIV Programmes

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Getting vaccinated against influenza is one of the most effective ways to prevent influenza and its complications. It also reduces the risk of serious illness or death from infection. With the concerted efforts of all sectors of the community (including the medical sector, schools, parents and residential care homes), as of December 28, 2025, over 1.89 million doses of influenza vaccine were administered under various SIV programmes in the year 2025/26, representing an increase of approximately 4.7 per cent compared with the same period in the previous influenza vaccination season. Regarding schools, to boost SIV rates, enrolment for the SIV School Outreach Programme has started earlier since the beginning of June last year. The CHP has also introduced enhancement measures, allowing all schools to choose either the live attenuated influenza vaccines (i.e. nasal LAIV) and the "hybrid mode", which allows schools to choose both the injectable inactivated influenza vaccines and the nasal LAIV during the same or different outreach vaccination activities. Vaccination rates among schoolchildren in different age groups are two per cent to nine per cent higher compared to the same period last year.

"The SIV coverage rate for children aged six months to under two years remains relatively low at about 22 per cent. Although this represents approximate five per cent point increase compared to the same period last year, it is still lower than that of other age groups. Through the Primary Healthcare Commission, the CHP has urged family doctors to assist in encouraging parents to give consent for their children to receive SIV. The Government has opened all 29 of the DH's Maternal and Child Health Centres (MCHCs) for all children aged six months to under two years to receive the vaccine; as well as the District Health Centres and District Health Centre Expresses and their service outlets under the Primary Healthcare Commission in the 18 districts, and 74 Family Medicine Clinics and 38 public hospitals of the Hospital Authority to provide more choices for the public. For the list of vaccination venues, please refer to the CHP's Vaccination Schemespage. Parents of eligible children may book an appointment for their children to receive vaccination at designated MCHCs via the  online booking system," Dr Tsui said.

He reminded the members of the public to maintain good personal, hand and environmental hygiene. Furthermore, high-risk persons should receive COVID-19 booster doses at appropriate times to lower the risks of serious illness and death. Public with respiratory symptoms, even if the symptoms are mild, should wear a surgical mask and seek medical advice promptly to lower the risk of spreading the disease to high-risk persons.

Members of the public may refer to the CHP's COVID-19 & Flu Express,Seasonal Influenza Webpage, COVID-19 Vaccination Programme Webpage, and Vaccination Schemes Webpage, for the latest information.

The Centre for Health Protection (CHP), Photo source: reference image

Update on chikungunya fever

The Centre for Health Protection (CHP) of the Department of Health announced that, as of 5pm today (January 4), no new cases of chikungunya fever (CF) had been recorded.

Latest surveillance data

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Hong Kong has recorded a total of 82 confirmed CF cases last year. Among them, 11 were local cases, and the rest were imported cases.

Since the beginning of 2025, and as of December 10, 2025, a total of 502 264 CF cases and 186 CF-related deaths have been reported in over 40 countries/territories. Cases have been reported in the Americas, Africa, Asia, and Europe. Although the northern hemisphere has entered the winter season, temperatures in subtropical and some temperate regions remain elevated due to climate change, creating favourable conditions for mosquito breeding. In addition, CF outbreaks continue to occur in many countries worldwide. The risk of imported cases persists. Members of the public should check the situation of the destinations before travelling abroad, especially when travelling to Southeast Asian countries.

Government's comprehensive follow-up actions

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Given that some local cases of CF have visited the Tsing Yi Nature Trails or the surrounding area in November last year, the trails are currently closed until further notice. Relevant government departments continue to conduct large-scale mosquito control and prevention efforts along the trails, and the CHP appeals to the public not to enter the area in order to reduce the risk of contracting CF and to avoid exposure to chemicals or interfering with the mosquito control operations. Since the confirmation on December 10, 2025, of a case involving a person who had visited the Tsing Yi Nature Trails on November 30, 2025, no further local cases have been recorded to date. The CHP continues to urge individuals who have recently hiked along the Tsing Yi Nature Trails to seek medical attention as soon as possible if they develop relevant symptoms and to call the enquiry hotline (Tel: 2125 2373), which operates from 9am to 6pm.

The Food and Environmental Hygiene Department (FEHD) has been continuously conducting intensive fogging operations to eliminate adult mosquitoes along the Tsing Yi Nature Trails and the surrounding area. At suitable locations, large ultra-low volume foggers have been deployed, and a robot dog is being put on trial to enhance operational effectiveness. The FEHD has also set up new mosquito trapping devices, cleared discarded containers and garbage that could cause stagnant water, and applied larvicide oil or larvicides in areas with stagnant water that cannot be removed immediately. The FEHD has been collaborating with the Kwai Tsing District Office, the Lands Department and the Drainage Services Department to strengthen efforts in eliminating potential mosquito breeding sites along the Tsing Yi Nature Trails. Pamphlets have been distributed to hikers in the area, urging citizens to be vigilant against mosquito infestations and take personal protective measures. The FEHD has also held meetings of the interdepartmental task forces on anti-mosquito work across districts to discuss the latest developments regarding the situation and plan accordingly to co-ordinate relevant departments and stakeholders in strengthening mosquito prevention and control measures in areas under their purview.

Continuously strengthening prevention and control

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The FEHD and relevant departments have comprehensively enhanced the mosquito control operations in Hong Kong since July last year, and this has continued. Among these, the FEHD has conducted vector investigations and targeted mosquito control operations against the imported and local cases. In light of the local case, the FEHD has immediately conducted follow-up actions, including:

carrying out intensive fogging in scrubby areas within a 250-metre radius of the relevant locations to kill adult mosquitoes;

carrying out inspections of the locations, removing stagnant water, applying insecticides and disposing of abandoned water containers every week with a view to preventing mosquito breeding; and

enhancing public education efforts through organising health talks, setting up mobile education stations, and distributing publicity leaflets.

The abovementioned measures will be continued. Furthermore, the Government will further enhance the mosquito control efforts in addition to the existing measures.

Preventive measures to be taken by the public

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Members of the public should use DEET-containing insect repellents or other effective active ingredients properly to prevent mosquito bites, but the following precautions should be taken when using them:

read the label instructions carefully first;

apply right before entering an area with a risk of mosquito bites;

apply on exposed skin and clothing;

use DEET of up to 30 per cent for pregnant women and up to 10 per cent for children (for children who travel to countries or areas where mosquito-borne diseases are endemic or epidemic and where exposure is likely, those aged 2 months or above can use DEET-containing insect repellents with a DEET concentration of up to 30 per cent);

apply sunscreen first, then insect repellent;

reapply only when needed and follow the instructions; and

in addition to DEET, there are other insect repellents available on the market containing different active ingredients, such as IR3535 and picaridin. When using any insect repellent, the public should follow the usage instructions and precautions on the product label.

The FEHD also 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 empty cans and lunch boxes. The FEHD also advises members of the public and property management agencies 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.

The public should call 1823 in case of mosquito problems, and may visit the following pages for more information: the CF page of theCHPand theTravel Health Service, the latestTravel Health News,tips for using insect repellents, and the CHPFacebook Page,Instagram AccountandYouTube Channel, and also theMosquito Prevention and Control dedicated pageof the FEHD.

Source: AI-found images